The influence of environmental factors and agricultural practices on wheat falling number

Abstract

English: Various environmental factors together with agricultural practices by producers that might contribute to reduced Hagberg Falling Numbers (HFN) of wheat, Triticum aestivum, in the absence of pre-harvest sprouting were simulated to determine whether HFN could be managed through specific management practices. Sufficient data have been generated to recommend that wheat should be allowed to dry to acceptable levels before they are harvested. Alpha-amylase activity could, however, not be successfully linked to reduced HFN at high kernel moisture content (KMC). Glyphosate treatments, administered at soft and hard dough stages to induce dry down of kernels at various KMC, produced more stable HFN for two of the three cultivars evaluated, but the optimal physiological growth stage resulting in the most stable HFN varied over seasons. Fifteen South African wheat cultivars were subjected to evaluation for their HFN response to various degrees of fertilizer application. No statistically significant effect on the HFN of wheat in general could be made. Cultivar differences did, however, occur that allowed for the individual effect of fertilizer on the HFN of these cultivars to be identified. This allowed for the grouping of cultivars into four response groups namely low, low to medium, medium and high response cultivars. Classification was refined with the use of a CVA (canonical variate analysis) that included the HFN, yield and protein response to fertilizer application. Recommendations regarding cultivar choice in areas prone to leaching can therefore be limited to cultivars that fall into the low and low to medium response groups identified in this study. Moderately high temperature exposure (32°C) during various grain filling stages of wheat resulted in reduced HFNs being measured. The physiological growth stage most affected by such temperatures, however, varied between cultivars. Further studies are suggested. In addition, farmers in areas that are known for their late frost should avoid planting early, as a study into the effect of a single night of low temperatures (–4°C) at late milk stage indicated that HFN could, as a result, be significantly reduced. A screening protocol was accordingly created to screen all cultivated varieties for such reactions, so that recommendations could be made as to which cultivars would be more tolerant to such conditions.Afrikaans: Verskeie klimaatsfaktore asook landboukundige-praktyke deur produseerders is ondersoek om die moontlike oorsake van lae Hagberg Valgetalle (HVGe) in die afwesigheid van uitloop te verklaar, asook om te bepaal of HVG sodoende deur spesifieke bestuurspraktyke gemanipuleer kan word om die beste moontlike HVG binne ‘n gegewe seisoen te verseker. Voldoende data is gegenereer om die aanbeveling te maak dat koring toegelaat moet word om natuurlik op die lande af te droog. Die effek van alfaamilase aktiwiteit by hoë vogpersentasies kon egter nie gekoppel word aan verlaagde HVGe wat waargeneem is nie. Glufosaatbehandelings, toegedien op sagte- en hardedeeg-stadia, was in staat om ‘n meer stabile HVG te lewer in twee van die drie cultivars wat geëvalueer is. Die spesifieke groeistadia waarop die behandelings gedoen is wat tot groter stabiliteit gelei het, het gewissel tussen seisoene. Vyftien Suid-Afrikaanse cultivars is ondersoek rakende hul HVG reaksie by verskillende bemestingsvlakke. Geen statistiese betekenisvolle effek kon egter aan bemesting en HVG gekoppel word as ‘n geheel nie. Cultivareffek het egter voorgekom, wat die indeling van die onderskeie cultivars in reaksiegroepe (laag, laag tot medium, medium en hoog) moontlik gemaak het. Klassifikasie is verfyn deur die gebruik van Kanoniese Variant Analiese (KVA) wat HVG, opbrengs asook proteïen reaksies op die verskillende bemestingsvlakke ingesluit het. Die groepering van die cultivars binne reaksiegroepe, skep egter die geleentheid om cultivaraanbevelings te maak in omgewings wat onderhewig is aan loging. Matige hoë temperature (32°C) gedurende die graanvullingstadia van koring het gelei tot betekenisvolle laer HVGe. Die fisiologiesegroeistadia wat die mees sensitief was, het tussen cultivars verskil. Addisonele studies in hierdie verband is egter noodsaaklik. Boere in gebiede wat bekend is vir laat ryp moet laat aanplantings vermy, aangesien ‘n enkele nag van lae temperature (-4°C) op laat melkstadia in staat is om HVG te verlaag. ‘n Protokol is saamgestel vir die evaluasie van cultivars vir rypsensitiwiteit sodat aanbevelings gemaak kan word rakende die graad van cultivartoleransie onder ryptoestande.