Maize response to in-field rainwater harvesting on the Fort Hare/Oakleaf ecotope

Abstract

The majority of rural households in the Eastern Cape Province struggle to meet basic needs especially in terms of household food security. Recent studies done in the Province indicate that agriculture contributes little to solve this problem especially in the villages around Alice. Despite poverty, most households rely on purchasing food from urban markets instead of producing food themselves. Crops are usually produced under dryland conditions by using mouldboard plough (conventional tillage) as the primary cultivation method. Research on clayey soils in semi-arid ecotopes showed that in-field rainwater harvesting technique (IR'WH) has potential to increase maize grain yield by up to 50% compared to conventional tillage (CON). The question was whether IRWH will also perform better than CON in the Alice district using Fort Hare/Oakleaf as a benchmark ecotope. The main aims of this study were to characterize important climate, soil properties and soil processes related to maize production on the selected ecotope and to compare the influence of IR WH treatments and CON on; (i) maize grain yield (ii) soil water balance components and (iii) crop-water related efficiencies. The ecotope was characterized in detail with respect to slope, long-term climate and soil characteristics. Long-term (27 years) climate data was used to analyze climate parameters which are related to maize production. A profile pit was dug next to the experimental plot and the soil was described in detail and classified using the South African Classification System. To compare the influence of IRWH treatments and CON on maize grain yield, a fully randomized complete block design experiment was used in 2004/05 and 2005/06 growing seasons. The three treatments viz. IRWH (with mulch), IRWH (without mulch) and CON were replicated three times. Maize cultivar PAN 6480 was planted at a population of 22 000 plants ha-¹. Since planting was done by hand, 32.5 g of fertilizer mixture 3:2:3 (22) + 0.5% Zn was applied per hole to supply 60 kg N ha-¹, 40 kg P ha-I and 60 kg K ha-¹. Evapotranspiration was calculated by using the soil water balance equation which depended on rainfall (measured with rain gauge), drainage (by comparing soil water measurements with drained upper limit), runoff (calculated) and change in soil water content (measured with neutron water meter). Grain yield was measured and crop-water related efficiencies were calculated. The results were used to compare maize response to three different treatments in terms of grain yield, soil water balance components and crop-water related efficiencies. The long-term climate data indicates that the ecotope qualifies as semi-arid due to high evaporative demand (1611 mm) and low rainfall (583 mm). The soil was classified as an Oakleaf form of the Ritchie family. The mean grain yield indicates that IRWH (with mulch) and IRWH (without mulch) produced 25 and 19% more grain than CON, respectively. The grain yield ranged from 2066 to 4373 kg ha-¹ over the two seasons. IRWH treatments had higher ET than CON at the end of both seasons. The low Es at the end of both growing seasons for CON was ascribed to the higher exfield runoff that decreased the available water for evaporation considerably. Cropwater related efficiencies' results followed the same trend as grain yield. It can be concluded that Fort Hare/Oakleaf ecotope is suitable for in-field rainwater technique due to its climate and soil properties. IR WH treatments were compared to CON and as hypothesized IR WH treatments performed better than CON in terms of to grain yield and crop-water related efficiencies. Mulch application increased grain yield by 25% compared to CON, while IRWH (without mulch) increased grain yield by 19% compared to CON Results showed that IRWH technique was able to harvest and store more rainwater than the CON due to the total stoppage of ex-field runoff.