Abstract
Erratic rainfall and temperature regimes, strongly affect agricultural productivity. To address the reduction in production, this study assessed the effect of Zai pit depths on selected soil properties and cowpea growth and grain yield. Zai pit technology was tested in two locations falling under Agroecological Zone IV (relatively dry areas) i.e. Machakos in Machakos County and Naivasha in Nakuru County, Kenya, aiming to determine the combined effect of four Zai pit depths and two levels of manure (plots with manure and plots without manure) on selected soil properties, growth and yield of cowpea. Experiment was laid out in split plot arrangement, with manure levels as the main plot factor and Zai pit depths (Flat: Z0, 30 cm: Z30, 45 cm: Z45 and 60 cm: Z60) as subplot factor, replicated four times. Cowpea (M66 variety) was used as the test crop. Inorganic nitrogen (Nin) and extractable phosphorus (Pex) were significantly (P ·kg−1 for Nin and 80.4 mg·kg−1 for Pex in Zai pits compared to flat plots which were at 0.91 mg·kg−1 for Nin and 47.1 mg·kg−1 for Pex. The values of Nin and Pex also varied depending on depths, with Z45 having highest Nin at 1.17 against the least, at 0.89 in the Z0, while Pex was highest in Z30 at 102.3 mg·kg−1 while Z0 having the least Pex of 89.7 mg·kg−1. Generally, crops in Zai pitted plots were larger in diameter (0.46 cm) and height (34.20 cm) than crops in flat plots at (0.42 cm) and (18.11 cm) diameter and height respectively. Better performance was observed in yield, with Z45 yielding 853.33 kg·Ha−1 against 685.0 kg·Ha−1 in Flat plots in Machakos while 931.66 kg·Ha−1 in Z45 against 563.33 kg·Ha−1 from Flat plots in Naivasha. This study demonstrated great potential of Zai pit technology on crop production, as reflected on improved growth and yield of cowpeas. Combining Zai pits with manure increases soil Nin, Pex and is a guarantee of great crop performance in terms of high final yields.
Highlights
Aridisols are degraded soils, mostly found in relatively dry areas experiencing unreliable rainfall regimes
Inorganic nitrogen (Nin) and extractable phosphorus (Pex) were significantly (P < 0.05) higher, at 1.37 mg∙kg−1 for Nin and 80.4 mg∙kg−1 for Pex in Zai pits compared to flat plots which were at 0.91 mg∙kg−1 for Nin and 47.1 mg∙kg−1 for Pex
This study demonstrated great potential of Zai pit technology on crop production, as reflected on improved growth and yield of cowpeas
Summary
Mostly found in relatively dry areas experiencing unreliable rainfall regimes. For farmers determined to cultivate these soils, they end up producing little that can only support their subsistence till production season, making it difficult for commercialization. With the current global warming, climate change is inevitable and aridisols continue deteriorating; farmers produce less than previously [2]. Reduction in rainfall intensity and duration results in low soil water storage, which reduces soil moisture availability that greatly affects crop production. Water is a critical factor of crop production and before planting, farmers have to consider its source. Some farmers are able to irrigate, while those who cannot afford rely on rainfed crop production, which are proven to reduce production expectations seasonally. Soil moisture conservation measures can be adopted, which include the use of Zai pit technology [3]
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