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

[摘要] The majority of rural households in the Eastern Cape Province struggle to meet basicneeds especially in terms of household food security. Recent studies done in theProvince indicate that agriculture contributes little to solve this problem especially inthe villages around Alice. Despite poverty, most households rely on purchasing foodfrom urban markets instead of producing food themselves. Crops are usuallyproduced under dryland conditions by using mouldboard plough (conventionaltillage) as the primary cultivation method. Research on clayey soils in semi-aridecotopes showed that in-field rainwater harvesting technique (IR'WH) has potential toincrease maize grain yield by up to 50% compared to conventional tillage (CON). Thequestion was whether IRWH will also perform better than CON in the Alice districtusing Fort Hare/Oakleaf as a benchmark ecotope.The main aims of this study were to characterize important climate, soil properties andsoil processes related to maize production on the selected ecotope and to compare theinfluence of IR WH treatments and CON on; (i) maize grain yield (ii) soil water balancecomponents and (iii) crop-water related efficiencies. The ecotope was characterized indetail with respect to slope, long-term climate and soil characteristics. Long-term (27years) climate data was used to analyze climate parameters which are related to maizeproduction. A profile pit was dug next to the experimental plot and the soil was describedin detail and classified using the South African Classification System. To compare theinfluence of IRWH treatments and CON on maize grain yield, a fully randomizedcomplete 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 werereplicated three times. Maize cultivar PAN 6480 was planted at a population of 22 000plants 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 whichdepended on rainfall (measured with rain gauge), drainage (by comparing soil watermeasurements with drained upper limit), runoff (calculated) and change in soil watercontent (measured with neutron water meter). Grain yield was measured and crop-waterrelated efficiencies were calculated. The results were used to compare maize response tothree different treatments in terms of grain yield, soil water balance components andcrop-water related efficiencies.The long-term climate data indicates that the ecotope qualifies as semi-arid due tohigh evaporative demand (1611 mm) and low rainfall (583 mm). The soil wasclassified as an Oakleaf form of the Ritchie family. The mean grain yield indicatesthat IRWH (with mulch) and IRWH (without mulch) produced 25 and 19% more grainthan CON, respectively. The grain yield ranged from 2066 to 4373 kg ha-¹ over thetwo 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 exfieldrunoff that decreased the available water for evaporation considerably. Cropwaterrelated efficiencies' results followed the same trend as grain yield. It can beconcluded that Fort Hare/Oakleaf ecotope is suitable for in-field rainwater techniquedue to its climate and soil properties. IR WH treatments were compared to CON andas hypothesized IR WH treatments performed better than CON in terms of to grainyield and crop-water related efficiencies. Mulch application increased grain yield by25% compared to CON, while IRWH (without mulch) increased grain yield by 19%compared to CON Results showed that IRWH technique was able to harvest andstore more rainwater than the CON due to the total stoppage of ex-field runoff.

[发布机构] University of the Free State