Soil, Crop and Climate Sciences

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Open Access
Studies oor die toeganklike fosforstatus van sekere Vaalhartsgronde
(University of the Free State, 1971-12) Eloff, Jacobus Frederick; Laker, M. C.
Afrikaans: Op die Vaalhartsbesproeiingskema is 30 veldproewe uit gelê om die toeganklike fosforstatus van die verteenwoordigende gronde te bepaal. Sitroensuur-P, Bray-P, Olsen-P, CAL-P en hars-P uit die grond geëkstraheer, is gekorreleer met plantmassas van Zambesi-koring op pypstadium, fosforopname op pyp en met oesopbrengs ten einde die geskikste metode vir die voorspelling van "plantbeskikbare" fosfor vir hierdie gronde te vind. Ander plantvoedingstofkonsentrasies (K, Ca, Mg en Zn) in die plante op die pypstadium is bepaal, terwyl die P-, K-, Ca-, Mg- en Zn-konsentrasies in die graan en die hoeveelhede verwyder deur die oes ook bereken is. Al die ekstraksieprosedures het hoogs betekenisvol (P=0,01) met mekaar gekorreleer, alhoewel die metode van Olsen deurgaans 'n laer korrelasiekoëffisiënt met al vier die ander metodes vertoon het. Hoewel alle metodes beteknisvol gekorreleer het met plantmassas op pypstadium, fosforopname en oesmassas het die Olsenekstraheerbare-P in alle gevalle, maar veral met oesmassas, die beste korrelasies gelewer. Hierdie metode word dan ook aanbeveel vir die bepaling van plantbeskikbare fosfor in die gronde onder bespreking, waarin die Manganoserie oorheersend is. Dit is bevind dat die fosforstatus van 64% van die bogronde van die bewerkte grond reeds voldoende opgebou is en dat slegs onderhoudsbemesting daar nodig is. Die ondergronde het in alle gevalle prakties gesproke geen "plantbeskikbare" fosfor bevat nie. Dit is baie duidelik dat fosforbeweging as gevolg van loging nie plaasvind in die gronde onder bespreking nie. 'n Insiggewende verwantskap is aangetoon tussen die KAV's van die kleifraksies van die bogronde en die kalum-, kalsium- en sinkkonsentrasies en K:Mg verhouding in plante op pypstadium. Hierdie verwantskap is ook bevestig deur die K-konsentrasies in die graan.
Open Access
Die geohidrologie in die opvanggebied van die Moloporivier in die Noordelike Kalahari
(University of the Free State, 1977) Smit, Petrus Jurgens; Grobler, N. J.
Afrikaans: Die gebied wat 58 153 km2 beslaan en waarvan ongeveer 75 persent met sand bedek is, is uitsluitlik van ondergrondse water afhankliko Die gesteentes le hoofsaklik in die westelike en suidelike dele blootgele Die Kalaharilae is tot 180 m dik en die geologiese formasies onder die Kalaharilae is volgens boorgatgegewena vasgestel Die diepte van die grondwatervlak varieer tussen 15 m in dagsoomgebiede en 150 m in gebiede waar die Kalaharilae die dikste is. In die westelike dele Is die Kalaharilae waterdraend. In stollingsgesteentes lewer 34 tot 50 persent van die boorgate meer as 450 l/h en in sedimentire geateenteep behalwe die Formasie Dwyka, 50 tot 80 perssnte Boorgate wat wetenskaplik op Voor-Kalaharigeeteentes gekies is lewer 10 persent hoer suksease (lewering meer Ba 450 1/h) 88 boorgate wat op ander metodes gekies is. In 38 boorgate is watervlakakommelinge sedert 1967 gereeld gemeeto Seisoensveranderinge is ongeveer 3 keer groter in boorgate in dagsoomgebiede aa in boorgate waar'die Kalaharilae tussen 0 en 15 m dik is. Waar die Kalaharilae dikker as 15 m is, is geen seisoensveranderinge waarneembaar nie. Die gebied kan volgens die hoogtekontoere van die grondwatervlak in 8 grondwatereenhede r ingedeel word wat elk 'n afsonderlike grondwaterkompartement vorm. Die temperatuur van die grondwater varieer volgens die diepte van die grondwatervlak. Die geotermiese gradient is hiervolgens bereken as 54 m/°C in graniet, 50 m/°C in dolomiet, 35 m/°C in jaspiliet, 30 m/°C in lawa en 45 rn/°C 1n Kalaharilae. In totaal ia 204 grondwatermonsters chemies ontleed en totale opgeloste stowwe ia In 655 monsters bepaelo Die konsentrasie van T.O.S. in die grondwater in Voor-Kalaharigesteentea word progressief hoer met 'n toename in die dikte van die Kalaharilae. Die Kalaharilae veroorsaak nie 'n verhoging in die konsentrasie van totale opgeloste stowwe in die grondwater nie maer ioonuitruiling vind wel plaas waar grondwater deur die kleilae beweeg. Die grondwater in die Voor-Kalaharigesteentes en in die Kaleharilae kan elk in 4 tipes ingedeel word volgens die chemiese samestelling en oorsprong. Die grondwateraanvulling in dagsoomgebiede varieer tussen 2,2 persent in die weste by ‘n reenval van 220 mm per jaar, tot 3,8 persent in die ooste, by ‘n reenval van 550 mm per jaar. In gebiede waar die bedekking tussen 0 en 15 m is, is aanvulling moontlik 0,5 persent van die jaarlikse reenval en waar die Kalaharilae dikker as 15 m is, vind geen direkte aanvulling plaas nie. Die totale jaarlikse aanvulling tot die grondwater in die hele gebied is 227,2 x 106m3• Die totale grondwaterverliese in die gebied is 52,498 x 106m3 per jaar, waarvan 70 persent uit boorgate en 30 persent uit fonteine afkomstig is. Die jaarlikse toename in die waterverbruik word beraam op 1,5 persent in Blanke gebiede en 8 persent in Tuialandgebiede. Die waterverbruik deur mense en diere verteenwobrdig 39 persent van die totale gl'ondwaterverliese, verbruik deur besproeiing 36 persent, deur dorpe en myne 20 persent en deur verdamping en transpirasie 5 persent. Net 62 persent van die totale fonteinvloei word direk benut. Die totale grondwaterverliese in, die gebied verteenwoordig 23 persent van die jaarlikse bruto aanvulling, maar varieer tussen 91 en 17 persent in die verskillende grondwatereenhede. Die totale hoeveelheid water wat uit boorgate onttrek word is 36,856 x 106m3/j of 16 persent van die totale jaarlikse aanvulling. Die toekomstige waterverbruik in die gebied word beraam op 114,l4 x l06m3/j vir die jaar 2000, wat ongeveer 50 persent van die jaarlikse potensiele aanvulling verteenwoordige Die benutting varieer egter tussen 31 en 132 persent in die' verskillende grondwatereenhede. Ten einde die grondwaterpotensiaal beter te bepaal is verdere navorsing nodig op die natuurlike aanvulling tot die grondwater in dagsoomgebiede, die optimale dikte van die bedekking in verhouding tot aanvulling, die ondergrondse vloei deur die dolerietgange in dolomiet en op die ondergrondse vloei uit sommige van die grondwatereenhede. Ondersoek is ook nodig op die ontginningspotensiaal en stoorkapaaiteit van die verskillende formasies insluitende die Kalaharilae wat oor groot gebiede ‘n belangrike akwifeer vorm. Die ontginning van grondwater vernaamlik in granietgelJiede is 'n wesenlike probleem en navorsing op metodes en tegnieke van boorplek aanwysing sowel as boorgatontwikkellng is nodig. In groot gebiede in die noordweste is die grondwater onbruikbaar sout en ontsouting van grondwater is ‘n baie belangrike aspek vir toekomstige benutting. Navorsing behoort ook gedoen te word op die ontwerp en beplanning van kunsmatige opvanggebiede ten einde reenwater in sekere gebiede direk te benut.
Open Access
Besproeibaarheid van gestruktureerde gronde
(University of the Free State, 1991-11) Nell, Johannes Petrus; Bennie, A. T. P.
Afrikaans: Data van 333 profiele se fisiese (breukmodulus, infiltrasie, hidrouliese geleivermoë, lugwaterdeurlatendheidverhouding, waterretensie en Atterberggrense), chemiese (KUK, UNP, NAV, pH, elektriese weerstand, elektriese geleivermoë, Fe-SBD, Al-SBD en organiese koolstof) , morfologiese (grondkleur, struktuur, kleiverhoudings en slik tot kleiverhoudings) en kleimineralogiese eienskappe was gebruik om neokutanies, pedokutanies, prismakutanies, rooi gestruktuurde en vertiese gronde te karakteriseer. Gronde van 15 dreineringstreke is in die ondersoek gebruik. Klem word egter op kalkryke gronde in die Sondagsrivier-, Klein-Visrivier- en Groot-Visrivierdreinerings- gebied geplaas, aangesien heelwat van die gronde deur verdere ontwikkeling van die Oranjerivierprojek geraak word. Daar bestaan regverdiging om verskille tussen diagnostiese horisonte as besproeiingsnorm te gebruik, aangesien duidelike fisiese en chemiese verskille tussen grondvorms, binne dreineringsgebiede voorkom. Daar is 'n afname in die geskiktheid van gronde vir besproeiing met 'n toename in graad van struktuurontwikkeling. Dit kan hoofsaaklik toegeskryf word aan 'n toename in opbou van skadelike soute en 'n verskuiwing van 'n oorwegend illietiese kleimineraalsamestelling na 'n smektietiese samestelling wat tot swelling en/of dispersie aanleiding gee. Laer infiltrasie en hidrouliese geleivermoë waardes, met 'n toename in struktuurontwikkeling, kan grootliks hieraan gewei word. Alhoewel die Na-inhoud ook 'n rol speel by die strukturele eienskappe van vertiese en rooi gestruktuurde gronde, het die tipe en hoeveelheid kleiminerale en seskwioksiedes 'n duideliker invloed by dié gronde se struktuurstabiliteit. Daar bestaan egter nie regverdiging om kleur volgens seriedifferensiasie as besproeiingsnorm by pedokutaniese gronde te gebruik nie. Die stabiliserende effek van die ysteroksiedes wat vir rooi grondkleur verantwoordelik is, word egter in sommige dreinerings- gebiede oorbeklemtoon. Die soort en hoeveelheid soute tesame met die tipe kleiminerale het 'n meer dominante invloed op hierdie gronde se struktuurstabiliteit. Die groot variasie in hidrouliese eienskappe van gestruktuurde gronde kan moontlik beter verstaan word, indien die beskrywing van die graad, tipe en grootte van die struktuureenhede met spesifieke parameters gekwantifiseer kan word. Die oorgang tussen horisonte is ook van belang. By dupleksgronde kom daar in die algemeen 'n drastiese afname in infiltrasie van die A- na die B-horisonte voor. Die lae infiltrasievermoë van die B- horisonte veroorsaak dat horisontale infiltrasie tot 'n groter mate as vertikale infiltrasie plaasvind. Aansienlike interkorrelasie tussen fisiese, chemiese en kleimineralogiese eienskappe kom voor wat tot lae verwantskappe aanleiding gee. Indien gronde egter in pedologiese eenhede gegroepeer word en die korrelasies vergelyk word, kan sommige daarvan verhoog of beter verstaan word.
Open Access
Die verdraagsaamheid van wildehawer vir onkruiddoders
(University of the Free State, 1993-03) Smit, Hugo Amos; Human, J. J.; Du Toit, D.
No abstract available
Open Access
A system for drought monitoring and severity assessment
(University of the Free State, 1995-02) Lourens, Uys Wilhelm; De Jager, J. M.
English: The objectives of this study were: (i) to develop a near real-time crop-specific drought monitoring system that delimits drought stricken areas and assesses the severity of droughts in these areas, (ii) to produce products from the system which can be used for decision support by decision makers, and, (ii) to test the system for maize production using historical production seasons. Objectives (i) and (ii) An agricultural drought monitoring system was designed, which combined crop growth modelling and a Geographic Information System (GIS) . The use of crop models made it possible to assess the drought damage suffered by crops, in relation to their growth stage. As drought is a spatially related phenomenon, a GIS was used to present the geographic distribution of a drought situation. A grid based, spatially distributed, system was designed. The map units of the South African 1.:250 000 map series were used as the base units on which to present information. Each base unit was divided into cells covering an area of 2' by 2' minutes of latitude and longitude. There were thus 1.800 grid cells in one such unit. The models were run for each of these cells. The data inputs required by the crop models therefore had to be spatially distributed. Methods of creating spatially distributed weather data bases, were implemented or developed. Existing interpolation techniques were used to create the rainfall and temperature data bases. A technique developed for determining daily irradiance, from the Japanese Geostationary Meteorological Satellite, was adapted for use on METEOSAT data obtained over South Africa. A spatially distributed soil data base was also created. Maize was chosen as the crop to monitor in the initial evaluation of the system. Drought monitoring was undertaken at fortnightly intervals from the beginning of the crop production season. At each interval, observed weather data was used up to the present date, and the season completed with surrogate data. Three surrogate scenarios were used: a below normal rainfall year, a normal rainfall year, and, an above normal rainfall year. Surrogate data were created for each homogeneous climate zone (HCZ) within the study area. The HCZ within which the cell lay was determined and its data used to complete the season. A rainfall data generator, the accuracy of which had been proved, was used in establishing the surrogate data. The cumulative probability distribution function (CDF) of seasonal yield, was used as the norm against which to measure current season performance at the conclusion of each monitoring session. CDF's were established for all combinations of soil, climate, and planting dates used within the bounds of a particular 1:250 000 map unit. The yield simulated for each cell was compared with the appropriate CDF, and the probability range within which it lay, determined. A drought index value was assigned based on this comparison. The indices were: 1- Extreme Drought (CDF probability range 0- 10%), 2- Severe Drought (>10- 20%), 3- Moderate Drought (>20- 30%), 4- Mild Drought (>30- 40%), and, 5 - No Drought (>40 - 100%). Maps showing the distribution, and tables providing the extent of area classified, were produced. Objective (iii) The drought monitoring system was tested for three maize production seasons. The accuracy of the system was determined by comparing the average maize yield per magisterial district with measured yield data. Individual farm records were also evaluated. The system accurately portrayed the general maize production trends during a severe drought (91/92}, while an r 2 of 0.59 was obtained for the individual yields. The crop modelling approach to drought assessment takes the interaction of the soil, plant and atmosphere into account and is crop specific. The important influence of both the amount and timing of rainfall in relation to crop growth stages is therefore reflected in the drought index.
Open Access
Parametric analysis to describe genotype x environment interaction and yield stability in winter wheat
(University of the Free State, 1997) Purchase, John Luscombe; Van Deventer, C. S.
No abstract available.
Open Access
Effect of spray volume, water quality, adjuvants and ammonium salts on sethoxydim activity
(University of the Free State, 1998) Chiconela, Tomás Fernando; Ceronio, G. M.; De Villiers, B. L.
The effects of spray carrier, pH, adjuvants and ammonium salts, environmental factors, and spray volume on sethoxydim {2-[ 1-ethoxyirnino-butyl]-5-[2-( etylthio )propyl]-3- hydroxy-2-cyclohexen-1-one} activity in a glasshouse on tomato (Lycopersicum esculentum L cv. Star 9001) and oats (Avena sativa L cv. SSH 241) were studied. Sodium bicarbonate, potassium carbonate and spray solution pH were antagonistic to sethoxydim phytotoxicity. Spray solution pH and ions present were antagonistic to sethoxydim phytotoxicity only when the spray carrier pH exceeded 6.5. Sadol and ammonium salts (ammonium nitrate and ammoruum sulfate) were equally effective in enhancing sethoxydim activity regardless of the presence of antagonistic salts. Bladbuff 5 was moderately effective in the enhancement of sethoxydim phytotoxicity only when sethoxydim was applied at 186.0 g ai.ha¹ and not at 139.5. Addition of Agral 90 and Break- Thru were not beneficial, or were both of little value as adjuvants with sethoxydim. Sethoxydim applications at temperatures ranging between 25 and 35°C were equally more effective as compared to 15°C. However, Sadol, Break- Thru and ammonium salts were most effective in enhancing sethoxydim performance at 25°C than at 15 or 35°C. When averaged across sethoxydim rates and the presence of sodium bicarbonate and in potassium carbonate in the spray solution, oat fresh top mass reduction increased as carrier volume was decreased from 875 to 175 l.ha¹. In all the experiments conducted, tomato plants did not show any injury to negative growth suggesting that sethoxydim may be considered for control of grass weeds in tomatoes.
Open Access
The compaction susceptibility of soils in the Free State
(University of the Free State, 1998-12) Nhantumbo, Alfredo Bernardino Julio Da Costa; Bennie, A. T. P.
Crop production in the Free State is mainly performed on sandy soils. The compaction of these apedal soils can present a management problem which affects crop yields and financial returns. In addition, environmental problems such as soil erosion and siltation of rivers may result. The main objective of the study was to see whether the easily measured soil properties, texture and organic matter, could be used to classify the compact ion degree of soils and to predict their compaction susceptibility. Additional objectives were to define critical densities beyond which crop growth would be impeded, to test the applicability of the relative bulk density concept proposed by Bennie & Van Antwerpen (1988) and to propose a procedure for the prediction and classification of the compactibility of the soils in the Free State. Finally, the results were compared to the data from forestry soils (Smith, 1995) for more humid conditions. Twenty two (22) samples of selected soils covering a large range of soil texture variation were submitted to a determination of the maximum bulk density (using the Proctor test), minimum bulk density, uniaxial compression test and penetrometer resistance measurements. A procedure for the determination of minimum bulk density was developed. Good quadratic relationships were obtained between the maximum bulk density and silt plus clay or organic matter content as loss on ignition. The minimum bulk density can be predicted from the silt plus clay percentage or loss on ignition. When the actual bulk density and the silt plus clay or loss on ignition percentages are available, the relationships allow the estimation of maximum and minimum bulk densities. The measured bulk density can then be used to calculate the relative bulk density of a soil. Threshold relative bulk density classes (5) were derived which can be used to evaluate the degree of denseness or looseness of the soil, and its suitability for different applications. It is proposed that compactibility be regarded as the difference between the maximum and minimum bulk densities, instead of simply the maximum bulk density. Different classes of compactibility were derived. The compression index of all the soils at the critical water content showed good relationships with the silt plus clay, clay or organic matter contents of the soils. Compressibility classes were also established. A combination of the compactibility and compressibility of soils was used to determine its susceptibility to compaction. Compaction susceptibility was classified into five groups varying from very low to very high degrees of susceptibility for apedal soils. The data set from this study when combined with the data reported from the study of forestry soils by Smith (1995), made it possible to derive equations with a more universal applicability for the prediction of the maximum and minimum bulk densities, critical water content as well as compression index. The results from this investigation, when properly transferred in popular terminology set guidelines for the evaluation of the degree of compactness and compaction susceptibility of soils. These guidelines will allow persons responsible for soil evaluation to draw more meaningful conclusions from bulk density measurements.
Open Access
Characterization of Yr15 resistance to stripe rust of wheat
(University of the Free State, 1999-12) Kotzé, Pieter Malan; Pretorius, Z. A.; Spies, J. J.; Viljoen, C. D.
English: Stripe (yellow) rust, caused by Puccinia striiformis Westend f. sp. tritici, is a major disease of bread wheat, Triticum aestivum L., in South Africa. The objective of this study was to evaluate the Yr15 gene as a potential resistance source for breeding purposes. Histological evidence was provided that Yr15 conditions a hypersensitive reaction typical of non-durable resistance. Fluorescence, phase contrast and scanning electron microscopy complemented each other and may be used to quantify various aspects of resistance expression in the wheat stripe rust pathosystem. The frequency of stomatal penetration was extremely low and no meaningful differences in early infection structures were observed between the resistant Yr15 and susceptible Avocet 'S' lines. Papillae were not involved in the resistance response to pathotype 6E16. In studies of defense-related proteins, an induction of β- 1,3-glucanase activity in both resistant and susceptible wheat genotypes was detected within 96 h post-inoculation (hpi). This induction, however, was constitutive and did not depend on the infection process. Likewise, no changes in chitinase activity were observed between resistant and susceptible plants. A pronounced increase of peroxidase activity between 0 and 168 hpi, in both infected and uninfected resistant and susceptible plants was observed, suggesting a constitutive expression of this enzyme. Using AFLP (Amplified Fragment Length Polymorphism) technology to detect possible molecular markers for Yr15, two primer combinations yielded polymorph isms between the bulked susceptible and resistant SST55 x Yr15/6*AvS F2 DNA, as well as between the susceptible and resistant parents. Fragment sizes ranged from 50 to 420 bp. Of these, one 95 bp fragment identified using primers MseCAA + Eco-ACA and one 205 bp fragment identified using primers MseCAA + Eco-AAC were detected in the resistant parent and the resistant F2 group. This indicates that these fragments are closely associated with Yr15 making them ideal candidates for further investigation.
Open Access
Chemical factors influencing dry bean yield
(University of the Free State, 2000) Molahlehi, Lebone; Pretorius, J. C.; Ceronio, G. M.
English: The abscission of the reproductive organs (flower buds, flowers and pods) of the common bean, Phaseolus vulgaris L., has proved to be a very serious problem affecting bean yields. The yield reductions are mainly significant under conditions of environmental stress, which aggravate production of the abscission causing hormones such as ethylene. The study therefore evaluated the effect of certain nutrients, other chemicals and ethylene (growth regulator) applied as foliar sprays to determine their effect in as far as abscission of the reproductive organs in beans is concerned. Glasshouse trials were carried out during the 1998/99 and 1999/00 seasons to investigate the possible preventative role of some micro and macro-nutrients, abscission inhibitors (e.g. Silver) and growth regulators (e.g. ethylene) all applied as foliar sprays. In another trial, three cultivars were compared where no treatments were applied. Data were collected and the following parameters were measured; number of flowers and pods that abscised, pods formed and abscised, pods that matured and could be harvested, dry pod mass at harvest, seed number per pod, dry seed mass per pod and total yield per hectare. Data were analyzed using a SAS software system and interpreted accordingly. The results of this study indicated that flower and pod formation might not be considered as the major factor affecting bean yields. The reason being that flowering percentage was not very different between the treated and the untreated plants. The abscission of flower buds, flowers and pods, however, was relatively high in general, indicating that this is possibly a primary factor affecting poor yields in beans. Ethrel, an ethylene releasing compound, applied as a foliar spray, aggravated the problem of flower and pod abscission. An ethylene antagonist (silver salt) had a slight alleviating effect on organ abscission but did not improve the final yield significantly. Molybdenum and potassium salts improved flower formation to a certain extent but had no real alleviating effect on organ abscission. This was also revealed in the lack of yield improvement. Foliar application of a copper salt as well as treatment with ComCat®, a natural product with biocatalytic properties, did not influence flower and pod abscission significantly, but increased the final yields to some extend. The latter indicates that other factors besides organ abscission could have had an effect on determining the final yield outcome. In the light of these findings, it is suggested that further studies be undertaken to test a wider range of chemicals for their potential to circumvent flower and pod abscission and improve bean yields. The latter could also include treatment at other growth stages, including post flowering. Other attempts could include an investigation into the effect of other known ethylene antagonists such as AVG (L-a.-(2-arninoethoxyvinyl)-glycinehydrochloride), an inhibitor of ethylene synthesis and NBD (2,S-norbornadiene), an inhibitor of ethylene action, on organ abscission and yield outcome in beans. As the results also showed that other factors besides organ abscission could have played a role in yield improvement, it might be worthwhile to investigate the effect of promising chemicals on physiological processes.
Open Access
Influence of nitrogen and potassium applications on the early growth and development of maize (Zea mays L.)
(University of the Free State, 2000) Emmanuel, Willie President; Ceronio, G. M.; Du Preez, C. C.
English: It is well known that appropriate band applications of N and/or K can result in optimum early growth and development of maize. Two pot experiments were conducted in a glasshouse at the University of the Orange Free State, Bloemfontein to determine the application levels at which the above mentioned phenomena occur. The first experiment was conducted to determine the influence of band placed N and/or K on the early growth and development of maize, while the second experiment was set up to determine the influence of K placement through banding, topdressing and a combination of banding and topdressing on the early growth and development of maize. The first experiment was conducted from January to March 1999 with the cultivar PAN 6479. Two types of soil were used in the experiment, viz. a sandy loam soil collected from Ficksburg and a sandy soil collected from Boshof The plant density was maintained at three plants per pot and the experiment was terminated four weeks after seedling emergence. A complete randomized design with a factorial combination consisting of two main factors, viz. four N and/or K band application levels which were replicated thrice, was used in this experiment. The application rates were the equivalent of 0, 20, 40 and 60 kg N or K.ha-¹ for a row spacing of 1.5 m. The aerial and subsoil plant parameters, as well as, the nutrient uptake by maize were measured to determine the influence of different N and/or K applications on the early growth and development of maize. All the plant parameters measured showed that the interaction of N and K applications had no significant influence on the early growth and development of maize. The best results were obtained with an application of 20 to 40 kg N.ha-¹• An application of 20 kg K.ha-¹ provided the best results. The second experiment was conducted from October to November 1999. With the exception of the fertilization procedure, all other aspects pertaining to the execution of this experiment were the same as those used in the first experiment. This experiment was terminated six weeks after seedling emergence. The experiment consisted of two main factors, viz. four levels and three methods of K application, arranged in a factorial combination in a complete randomized design with four replications. The application rates were the equivalent of 0, 20, 40 and 60 kg K.ha-¹ placed through banding, topdressing and a combination of banding and topdressing for a row spacing of 1.5 m. With regards to the combination application, half of K was banded and another half topdressed. The aerial and subsoil plant parameters, as well as, the nutrient uptake by maize were studied to determine the effect of different levels of banded, top dressed and a combination of banded and topdressed K on the early growth and development of maize. All the plant parameters studied showed that the interaction of K application levels and methods had no significant influence on the early growth and development of maize. It seems the best results were attained with °to 20 kg K.ha-¹ The second experiment was conducted from October to November 1999. With the exception of the fertilization procedure, all other aspects pertaining to the execution of this experiment were the same as those used in the first experiment. This experiment was terminated six weeks after seedling emergence. The experiment consisted of two main factors, viz. four levels and three methods of K application, arranged in a factorial combination in a complete randornized design with four replications. The application rates were the equivalent of 0, 20, 40 and 60 kg K.ha-¹ placed through banding, topdressing and a combination of banding and topdressing for a row spacing of 1.5 m. With regards to the combination application, half of K was banded and another half topdressed. The aerial and subsoil plant parameters, as well as, the nutrient uptake by maize were studied to determine the effect of different levels of banded, top dressed and a combination of banded and topdressed K on the early growth and development of maize. All the plant parameters studied showed that the interaction of K application levels and methods had no significant influence on the early growth and development of maize. It seems the best results were attained with °to 20 kg K.ha-¹. A combination of banding and topdressing in the sandy loam soil and topdressing alone in the sandy soil provided the best results. Finally, it is recommended that field trials should be conducted in order to verify these glasshouse results under field conditions.The second experiment was conducted from October to November 1999. With the exception of the fertilization procedure, all other aspects pertaining to the execution of this experiment were the same as those used in the first experiment. This experiment was terminated six weeks after seedling emergence. The experiment consisted of two main factors, viz. four levels and three methods of K application, arranged in a factorial combination in a complete randornized design with four replications. The application rates were the equivalent of 0, 20, 40 and 60 kg K.ha-¹ placed through banding, topdressing and a combination of banding and topdressing for a row spacing of 1.5 m. With regards to the combination application, half of K was banded and another half topdressed. The aerial and subsoil plant parameters, as well as, the nutrient uptake by maize were studied to determine the effect of different levels of banded, top dressed and a combination of banded and topdressed K on the early growth and development of maize. All the plant parameters studied showed that the interaction of K application levels and methods had no significant influence on the early growth and development of maize. It seems the best results were attained with °to 20 kg K.ha-¹. A combination of banding and topdressing in the sandy loam soil and topdressing alone in the sandy soil provided the best results. Finally, it is recommended that field trials should be conducted in order to verify these glasshouse results under field conditions.. A combination of banding and topdressing in the sandy loam soil and topdressing alone in the sandy soil provided the best results. Finally, it is recommended that field trials should be conducted in order to verify these glasshouse results under field conditions.
Open Access
Effect of seed size, treatment and sowing depth on quality and yield of Ethiopian wheat (Triticum Spp.), faba bean (Vicia faba L.) and chickpea (Cicer arietinum L.) cultivars
(University of the Free State, 2000-11) Mengistie, Demissie Mitiku; Pretorius, J. C.; Van Niekerk, F.
English: This study was undertaken in an attempt to obtain information on the quality of seed produced by some of the important crops grown in Ethiopia. Bread and durum wheat was chosen amongst cereals while chickpea and faba bean represented pulses. For all crops two cultivars were included except in the case of durum wheat where a third South African cultivar was additionally investigated. All experiments were carried out at the Small Grain Institute, Bethlehem, South Africa under laboratory and field conditions. The main objectives of this study were 1) to classify seeds of each crop into three different sizes (small, medium and large) and to characterize seeds in terms of kernel mass, hectolitre mass, moisture content and protein content where applicable, 2) to determine the differences in germination potential of untreated seeds and seeds treated with different fungicides under laboratory and field conditions, 3) to evaluate the field performances of different seedlots, including yield components, by means of agronomic parameters, 4) to investigate the effect of two different sowing depths on emergence, seed yield and other yield components and 5) to statistically determine cultivar, seed size, fungicide treatment and sowing depth interactions in a variety of ways. Of the two Ethiopian bread wheat cultivars, Mitikie outperformed Kubsa under laboratory and field conditions for most of the seed quality parameters evaluated. The main reason appeared to be the fact that deeper planted seeds performed well, probably due to longer coleoptile lengths of seedlings, which in turn was positively associated with strong and taller plants. When soil moisture is minimal, as is the case in semi-arid regions, it is possible to plant seeds of this variety deeper than normal in order to utilize soil moisture better. On average, small sized bread wheat seeds performed worst of all and large sized seeds best in terms of most of the measured parameters. Large seeds contributed to a 13.8% increase in seedling emergence and produced plants with a 22.1 % higher yield as well as 11.8% increase in above ground biomass. The effect of fungicides on the field performance of bread wheat seeds was less pronounced as compared to that of seed size. Seedling emergence from shallow planted (5 cm) bread wheat seeds was much better than from deep planted (9 cm) ones. However, although the seed protein content of seeds harvested from plants grown from deep plantedseeds were higher than that from shallow planted ones, shallow planting is still recommended for the Eastern Free State area on grounds of the overall performance of these seeds observed in this study. Durum wheat cultivars performed in a similar fashion as bread wheat. Seedlings of semi-dwarf durum wheat cultivars, as was the case for semi-dwarf bread wheat cultivars, showed longer root lengths than did the tall cultivars. Moreover, seeds from the semi-dwarf cultivar, Gerardo, produced taller plants than Orania and outyielded both other cultivars. Some weevil damage was observed in seeds of Kilinto and therefore its true performance could not be evaluated properly. Large sized durum wheat seeds outperformed the medium and small ones in most respects. Fungicide treatments also had an improving effect on seed performance compared to untreated control seeds. Seedling emergence was also greatly improved by shallow planting and this was reflected in significantly higher yields. The seed protein content, as was the case in bread wheat, were significantly higher in seeds harvested from plants grown from deep-planted seeds except in the case of Gerardo. Seed treatment with Vitavax Plus, together with deep planting, had the most significant increasing effect on the protein content in durum wheat seeds. In comparing the two faba bean cultivars, it was clear that Kuse outperformed Cs 20dk in terms of most of the evaluated parameters under both laboratory and field conditions. Similar to the previous two crops, large sized seeds appeared to outperform the other two seed size groups in most respects. However, surprisingly the small sized seeds produced seedlings with longer epicotyls but this had no real effect on the other quality parameters. Moreover, the fungicide Dividend also had some improving effect on the germination of faba bean seeds. Celest, however, significantly reduced the root length of seedlings compared to the other treatments, and also on grounds of the outcome observed by means of other parameters, Celest is not recommended for treatment of faba bean seeds. Deep planted (10-12 cm) faba bean seeds outperformed the shallow planted ones in many respects and deep planting is therefore recommended. In chickpea, none of the fungicide treatments improved the field performance of seeds. Dividend treatment rather reduced seedling root length. As in the case of bean, deepplanted seeds (10 cm) performed better than shallow planted ones (5 cm). In general, and in most respects, laboratory and field data correlated well. Moreover, recently released cultivars of all crops investigated, outperformed the older ones. This emphasises the need for replacing older cultivars with newer ones on a larger scale in Ethiopia. Large sized seeds are preferred to medium and the medium to small ones for all the crops investigated. Shallow planting for Ethiopian wheat cultivars, but deep planting for pulse cultivars, is recommended. Seed treatment with fungicides is imperative in wheat crops but is not as critical in pulse crops.
Open Access
Hydrogeology of the Table Mountain sandstone aquifer - Klein Karoo
(University of the Free State, 2001) Kotze, Johanita Christelle; Van Tonder, G. J.; Verhagen, B. T. H.
Abstract not available
Open Access
The response of small white bean (Phaseolus Vulgaris L.) to different nitrogen and molybdenum fertilizer applications
(University of the Free State, 2001-09) Araremme, Daba Feyisa; Pretorius, J. P.
English: Dry bean production is normally associated with high soil fertility rich in organic matter content. However, dry beans are not exhibited dramatic improvements of seed yield through the development of high yielding cultivars, improved cultural practices and the use of external inputs, especially fertilizers when compared to other crops. The current acute bean shortage resulted in the need for better production systems to increase yield through fertilization. This study was therefore conducted with the objectives of investigating the role of N and Mo fertilizers in determining the growth and yield of beans, the different rates of N in band and broadcast placement methods that can give optimum yield, and the amount of total protein and total Mo found in the dry seeds as a result of the applied fertilizers. Two separate pot experiments of band and broadcast placement of N in different rates with and without Mo were executed during 2000/2001 growing season in the glasshouse at the University of the Free State, Bloemfontein, South Africa. Each pot was filled with red brown soil and planted to a dry bean cultivar, PAN 181. The plant density was maintained at three plants per pot. A completely randomized design with factorial combination consisting of four N levels (0, 20, 40 and 60 kg N ha") and three Mo treatments (0, 100 g Mo ha" leaf spray and 100 g Mo ha" seed treatment) replicated four times was used in the experiment. The results obtained indicated that the application of N and Mo fertilizers did not significantly affect the vegetative growth as well as the reproductive development of the tested dry bean cultivar. However, the application of N in band placement with Mo treatments affected seed yield more than the broadcast placement. With the band N placement method, higher seed yield was achieved at 60 kg N ha" with seed treated Mo while that of broadcast N placement was at zero N with seed treated Mo. With regard to the nutrient content of the dry seeds, higher seed total protein was obtained at 60 kg N ha" with zero Mo in banded N and at zero N with seed treated Mo in broadcasted N. Higher seed Mo content was achieved at 60 kg N ha" with seed treated Mo in band N placement whereas in broadcast N placement it was at zero N with seed treated Mo. Finally, further field trials are recommended in order to verify the glasshouse results under field conditions.
Open Access
Development of an index for wheat stripe rust infection
(University of the Free State, 2001-11) De Wet, Linda; Walker, S.; Pretorius, Z. A.
English: The main objective of this project was to develop an early warning index for infection of stripe rust (Puccinia striiformis f. sp. tritici) in susceptible cultivars of wheat (Triticum aestivum) for the main wheat growing areas of the R.S.A. Various authors are in agreement that temperature and moisture are the major climatic factors necessary for infection by stripe rust. Temperature limits from the literature vary between -4 and 30°C and no cut-off values were available. It was therefore decided to run an experiment to observe infection of stripe rust under conditions of high relative humidity and a range of temperatures, namely 5°C, 10°C, 15°C and 20°C. Results from the experiment indicated that little or no infection occurred for the 20°C temperature level and for exposure time periods of one hour or less. Exceptions occurred when sudden drops in temperature with removal of plants from growth chambers to the glasshouse took place. For both incidence and severity, it was found that temperatures greater than 22°C inhibited infection. The Pan 3349 cultivar was found to exhibit higher incidence than Karee. The statistical analysis shows significance for severity for Experiment 1 and 2, but not for incidence. Temperatures for Experiment 2 were slightly lower than those in Experiment 1 and could be explained by the presence of the fans in Experiment 2, to allow evaporation of dew from the sensors, allowing the sensors to register correct readings. The resulting higher moisture conditions in the still air In Experiment 1 could have contributed to the higher severity observed in Experiment 1. Conditions in the laboratory are not the same as in the field and possibilities for infections at higher temperatures in the field have been reported by Park (1990). He warned against extrapolation of results from the laboratory to the field, but it was nevertheless decided to use the results from the experiment as a basis for the development of an index for stripe rust infection of susceptible wheat cultivars in South Africa. Values of 14 day total degree days (TDDI4) were calculated from total degree hours (TDH) acquired from the experiment. TDDl4 for the experiment was calculated by summing degree days (DD) from inoculation until 14 days and relating them to average incidence observed on day 14. Two linear regression lines were obtained, one for 5°C 15°C temperature level and the other for the 15 °c - 20°C temperature levels. A cut-off TDDl4 value of 227 where the two lines crossed indicated 67 % cut-off value for incidence. TDDl4 was developed from this information and reads as follows: IfTDDI4> 227, then risk of incidence is low at < 67 %. IfTDDl4 < 227, then risk of incidence is high at > 67 %. TDDl4 was validated by testing on 1996 - 1998 and 1999 - 2000 data. Correct prediction values for highest and average incidence observation were 50 % and 29 % for 1996 - 1998 data (Table 4.7) and 40 % and 33 % for 1999 - 2000 data (Table 4.8). TDDl4 however, was thought to be impractical, so TDD7 was developed by using TDD7 for 7 days from a wet period. TDD7 = 128 was found to be 1.77 times less than the value for TDDl4 = 227 and so this value of 128 was used as the cut-off value. TDD7 thus reads as follows: If TDD7 > 128, then risk of incidence is low at < 67 %. If TDD7 < 128, then risk of incidence is high at > 67 %. TDD7 was validated using the 1999 - 2000 data, with total correct predictions of 53 % and 40 % (Table 4.10). It was therefore decided that TDD7 could be used by the producer as an early warning index, although the index would have to be tested in the field so that necessary improvements could be made. It is recommended that research on stripe rust-environment interaction be continued, also to include other diseases and the recommendations made in Chapter 2. Another possible recommendation would be to plan a refined laboratory experiment with a mechanistic approach to use a constant temperature data determined model in real life situations. Temperature and RH would vary and the results should be useful to producer, as well as the researcher. A model suitable for various other diseases as well, could be of great benefit when the cost of pesticides and fungicides are taken into account. The successful application of such a model would be of great benefit to all. After all, food is our fuel and sustainable production of high quality foodstuffs is essential to our survival.
Open Access
Micrometeorology and physiology of sugarcane crop during water stress
(University of the Free State, 2001-11) Koonjah, S. S.; Walker, S.; Singels, A.; Van Antwerpen, R.
Water stress is the single most important factor limiting yield in plants. The effects of water stress on the micrometeorology and physiology of sugarcane were investigated using the rainshelter facilities provided at the South African Sugar Association Experiment Station, Mount Edgecombe. Sugarcane variety NCo37 6 was stressed at the age of seven months during the first ratoon crop. Plant extension rate (PER) together with microclimatic measurements including radiation interception, and leaf and canopy temperature were measured continuously. Photosynthesis and leaf water potential were also measured on a daily basis together with the volumetric soil water content. Among the yield-determining processes, plant extension rate was the first to be significantly affected 10 days after onset of water stress. The leaf water potential (ΨL measured at this stage was -0.7 MPa. Leaf area index and radiation interception were the next processes to be affected. A significant decrease in photosynthetic rate occurred 19 days after onset of water stress when the ΨLwas at -1.0 MPa. More than 50% reduction in radiation use efficiency occurred 24 days after imposing water stress and the ΨLmeasured at this stage was -1.5 MPa. Recovery from the first stress as far as plant extension rate and photosynthesis were concerned, occurred within 3 to 4 days after irrigation was resumed. When the same sugarcane plants were stressed for a second time, it took fewer days for plant extension rate and photosynthesis to be severely affected as compared to the stress imposed during the first time.
Open Access
Organic matter restoration by conversion of cultivated land to perennial pasture on three agro-ecosystems in the Free State
(University of the Free State, 2002-01) Birru, Tilahun Chibsa; Du Preez, C. C.; Hensley, M.
English: Understanding the process of organic matter degradation and restoration is important with regard to sustainable agricultural production on any agro-ecosystem, and of particular importance where degradation is relatively rapid, such as in the coarse textured savannah soils of the South African highveld. Organic matter degradation studies on such soils in three agro-ecosystems, Harrismith, Tweespruit and Kroonstad, have been undertaken by Du Toit et al. (1994), and Lobe et al. (2001). This study is concerned with organic matter restoration on the same agro-ecosystems, and is therefore complementary to the two earlier studies. The objective was to investigate organic matter restoration at three depths, 0-50, 50-100 and 100- 200 mm, on perennial pastures of different ages that had been established on lands which had been cultivated continuously for more than 20 years. Representative C and N values for degraded lands and virgin grasslands for the three agro-ecosystems were obtained from the studies of Du Toit et al. (1994) and Lobe et al. (2001), and used as reference values. To reduce within-site error samples were collected at six places, separated from each other by a few meters, at each site. At each of these places six subsamples of each layer were taken to make up the final sample. There were therefore 18 soil samples per site. A total of 28 sites, ranging in ages from 4 to 25 years, were identified and sampled on the three agro-ecosystems, All the samples were analyzed for C and N, and selected samples were analyzed to characterize the soil fertility levels and particle size distribution at each site. Results showed a wide variation in the rate of organic matter restoration between sites in each of the agro-eco systems , due mainly to differences in natural resource factors and management techniques. Most important of the latter was the application of N fertilizer. Where this was inadequate or absent, very low organic matter restoration rates were generally measured. An approximate threshold value of available N below which organic matter restoration is severely impaired appears to be about 15 mg kg". On pastures up to the age of25 years most of the C and N storage has been in the 0-50 mm layer, a little in the 50-100 mm layer, and very little in the 100-200 mm layer. This observation accentuates the importance of the sampling depth in such studies. These results are in accordance with those of Potter ef al. (1999). The mean C gains over all the sites in the three agroecosystems, excluding those with a Nfertility level considered too low to initiate efficient C sequestration, is 0.56 Mg ha-I yr' as compared to 0.8 Mg ha" yr" suggested by Bruce el al. (1999) for the United States of America and Canada. The relatively coarse texture of the Free State soils, and the lower aridity indices, may account for the difference. An attempt was made by pooling the data for the three agro-ecosystems, and adopting a normalization procedure, to identify common C and Nrestoration curves with time. Although a definite upward trend is visible, large inter-site variation and the shortage of data points above 20 years results in relatively low correlation coefficients and the curves being unreliable at their top end. Further research to obtain data from very old pastures is recommended, as well as ecotope specific research on benchmark ecotopes to define in a reliable way the shape of the organic matter restoration curve.
Open Access
The effect of crop residue cover and soil texture on crusting
(University of the Free State, 2002-10) Massingue, Felicidade Isabel; Bennie, A. T. P.
Large areas of cultivated soils throughout the world develop rainfall-induced soil crusts. The soil crusts are usually the cause of reduced seedling emergence. To have quantitative information on the factors influencing the development of surface crusts and on the influence of ameliorating treatments on crust strength is valuable. The objectives of this study were firstly, to determine the influence of soil texture on the susceptibility of different soils for crusting; secondly, to quantify the effect of soil crusts on the emergence of wheat, sorghum, soybean and sunflower; and thirdly to determine the optimum level of crop residues that can be used as a mulch to mitigate the effect of soil crust strength. Five soils ranging in texture from sand to loam were sampled from the surface (0 - 200 mm). The soil samples were used in four greenhouse pot experiments that were conducted to examine the effect of crust strength on seedling emergence. Separate pot experiments in the greenhouse were conducted to determine how particle size distribution was related to soil crust strength. Regression analyses showed that silt, silt plus clay and clay contents were related to crust strength as indicated by modulus of rupture, penetration resistance and emergence force. All the relationships were of third order polynomial nature. The crust strength increased initially with increasing silt plus clay contents up to about 35 to 40 %, or clay contents up to about 25 %, then declined as a result of cracking that occurred upon drying. The emergence of wheat, soybean and sunflower was little affected at crust strengths less than 0.7 Mpa or 500 gf when measured as penetration resistance and emergence force respectively. Above these values seedling emergence decreased linearly with increasing crust strength. Large areas of cultivated soils throughout the world develop rainfall-induced soil crusts. The soil crusts are usually the cause of reduced seedling emergence. To have quantitative information on the factors influencing the development of surface crusts and on the influence of ameliorating treatments on crust strength is valuable. The objectives of this study were firstly, to determine the influence of soil texture on the susceptibility of different soils for crusting; secondly, to quantify the effect of soil crusts on the emergence of wheat, sorghum, soybean and sunflower; and thirdly to determine the optimum level of crop residues that can be used as a mulch to mitigate the effect of soil crust strength. Five soils ranging in texture from sand to loam were sampled from the surface (0 - 200 mm). The soil samples were used in four greenhouse pot experiments that were conducted to examine the effect of crust strength on seedling emergence. Separate pot experiments in the greenhouse were conducted to determine how particle size distribution was related to soil crust strength. Regression analyses showed that silt, silt plus clay and clay contents were related to crust strength as indicated by modulus of rupture, penetration resistance and emergence force. All the relationships were of third order polynomial nature. The crust strength increased initially with increasing silt plus clay contents up to about 35 to 40 %, or clay contents up to about 25 %, then declined as a result of cracking that occurred upon drying. The emergence of wheat, soybean and sunflower was little affected at crust strengths less than 0.7 Mpa or 500 gf when measured as penetration resistance and emergence force respectively. Above these values seedling emergence decreased linearly with increasing crust strength.
Open Access
Biokatalitiese komponente in sade van enkele spesies uit die families Fabaceae en Caryophyllaceae
(University of the Free State, 2002-11) Du Plessis, Helena Aletta; Pretorius, J. C.; Potgieter, G. P.
English: In the south of Germany it was observed that species of the families Fabaceae and Caryophyllaceae survived an unknown environmental catastrophy while this was not the case with plant species from other families (Huster, Personal observation). Seed suspensions of some species belonging to these two families were applied to agricultural crops as foliar sprays, improving both the vegetative growth and yield of the crops. This supplied the rationale to test the seeds of South African species from these two families for its biocatalytic properties. Seeds of two species from each of the mentioned families namely Acacia karroo and Acacia erioloba from the family Fabaceae as well as Pollichia campestris and Dianthus basuticus from the family Caryophyllaceae, were subsequently screened for similar biocatalytic properties. Not much information on the chemical composition of these four plant species and nothing at all about their biocatalytic activity could be found in literature. In the study that followed biocatalytic activity was confirmed in a seed suspension of Acacia erioloba (Fabaceae) as it increased the respiration rate of a mono culture yeast cells as well as root growth of Cress-seedlings markedly. Activity directed liquid-liquid extraction of the A. erioloba seed suspension revealed that most of the biocatalytic activity was present in the ethyl acetate fraction. Further column chromatographic fractionation of the ethyl acetate fraction produced 13 combined column fractions of which two were active. Activity directed preparative thinlayer chromatographic purification of compounds in one of these fractions produced one active compound that was identified as 2-ethylhexylphtalate by means of nuclear magnetic resonans (NMR) spectroscopy. From the second column chromatography fraction six compounds were isolated but in such small amounts that NMR analysis was not possible. By means of colour reagents it was, however, established that three of the six compounds were alkaloids, two were terpenoides and one a coumarin. It is recommended that active components in this group should be identified in a follow-up study by initially extracting much more seed material.
Open Access
Improvement of the nitrogen content of grape must with fertilisation
(University of the Free State, 2002-11) Jordaan, Jacques; Engelbrecht, G. M.; Du Preez, C. C.
English: Stuck fermentation is currently a serious production associated problem in the South-African wine industry. This can mainly be attributed to insufficient levels of nitrogen in grape must, thus are not being able to supply in yeast demands. This study was undertaken to investigate whether the nitrogen content of grape must can be improved by fertilisation. In order to achieve this three nitrogen application treatments (N1C = 20 kg N/ha-¹ post-harvest; N2F = 20 kg N/ha-¹ post-harvest, followed with 20 kg N/ha-¹ after budbreak and fruitset respectively; and N2V = 20 kg N/ha-¹ post-harvest, followed with 20 kg N/ha-¹ after budbreak and veraison respectively), were applied to six grape cultivars (Cabernet Sauvignon, Chenin blanc, Pinot noir, Weisser Riesling, Chardonnayand Pinotage) for two seasons (1999/2000 = 1st season and 2000/2001 = 2nd season). The vineyard is situated on a high potential loam soil, classified as a red-brown Oakleaf, with a mean organic matter content of 1.4%. The effect of these nitrogen application treatments on the growth characteristics, grape must composition, leaf nitrogen content, as well as the soil nitrate content, were measured. Nitrogen applications during the vegetative phase had a positive effect on the shoot length and shoot elongation during both seasons, although more so during the 1st season. The pruning mass was significantly affected by cultivar during both seasons. Treatments receiving no nitrogen fertilisation during the vegetative phase (N1C) resulted in higher free amino nitrogen (FAN) and FAN/oB ratio in grape must, indicating a negative reaction to nitrogen fertilisation for soils having a high organic matter content. No nitrogen fertilisation during the vegetative season resulted in significantly lower bunch and berry mass values than those receiving fertilisation. This might indicate a negative relationship between bunch and berry mass and the FAN content of grape must. The nitrate content of the soil differed for the different soil depths and was affected by sampling date and N treatments. Results indicated that 70% of the nitrate was available in the top 30 cm of soil. Nitrogen fertilisation during the vegetative season on soils with an organic matter content of 1.4% should be strongly discouraged. This study therefore indicates that although high organic matter content and inorganic fertiliser applications may increase the nitrate content of the soil, this might not have the same effect on the nitrogen status of the vine.