Effects of Zai pit technology (tumbukiza) on soil moisture conservation for cowpea ( vigna unguiculata l. walp) production in dryland areas of Kenya

Abstract

Zai pit technology (T umbukiza) is a water harvesting technique that uses micro pits dug in the farms to collect water to support plants throughout the growing season. In this study, Zai pits were used in two ASAL locations in Kenya, to grow cowpeas (Vigmz unguiculata L.) as the test crop, with the main aim of determining the combined efifect of Zai pit technology and manure on selected soil properties, growth and yield of cowpea; to determine the effect of Zai pit technology on soil moisture dynamics and water use efficiency (WUE) of cowpea (Vigna zmguiculata L. Walp) in ASAL localities; and lastly, to assess gross margin of using Zai pit technology for soil moisture conservation in cowpea production. RCBD layout in split — plot amrngement was used, where Cow manure was the main plot factor while subplot factors were the various Zai pit depths of 30 cm (Z30), 45 cm (Z45), 60 cm (Z40) and flat fields (Z0), that is, plots Without the technology to act as control (farmer practice). Data was analysed using Statistical Analysis software (SAS), version 9.2 and means separated using Tukey’s Honestly Significant Difference (HSD). Inorganic nitrogen (Nin), and extractable phosphorus (Pm). Varied significantly (P 5 0.05) with Zai depth, with Z45 having highest Ni“ at 1.17 against the least, at 0.89 mg kg" in the Z0, while Pa was highest in Z30 at 102.3 mg kg" while Z0 having the least Pcx of 89.7 mgkg". Soil moisture (v/v), evaluated weekly, increased to 375% in Naivasha and 418% in Katumani cumulatively. Manure brought significant effect to the plant height, highest at 32.9 cm and stem diameter of cowpea, largest at 0.51 cm. Water use efiiciency (WUE) was significantly (P 5 0.05) different across Zai treatments with Z45 having the highest of 14.51 kg I-Ia"mm“ while flat plots (Z0) producing least of 7.76 KgHa"mm‘l. Similarly, gross margin was varied significantly across Zai treatments, with Z45 performing better, yielding KES. 57,167 per hectare, against KES 9,245 per Ha from flat plots in Naivasha while in Katumani, Z60 producing the highest GM of KES 48740 per Ha while flat farms making a loss of KES 3067 per Ha. The study revealed that Zzi pit technology improves soil environmental conditions hence higher grain yields fioru Zai pitted plots, with Z45 yielding 853.33 kg.Ha" against 685.0 kg.Ha" in Flat plots in Katurnani while 931.66 kg.Ha" in Z45 against 563.33 kg.Ha'l from Flat plots in Naivasha From this study, use of Zai pits enhances yields, WUE and is profitable for cowpea production in AEZ IV. Further studies in other AEZs and with other crops should be conducted to generate recommendations for scaling out the use of this technology.