Effectiveness of soil moisture conservation techniques in sorghum under spate irrigation in Ewaso Nyiro south drainage basin

Abstract

Crop production is influenced by on-site soil moisture availability and application of water conservation methods for dry areas. This research explored the interactive effects of spate irrigation as an application method and the soil moisture conservation techniques. The objective of this research was to analyze the effectiveness of soil moisture conservation techniques and its correlation to water productivity for sorghum production under spate irrigation. The soil water holding capacity was investigated based on four moisture conservation techniques; mulching, ridging, ridge-furrow mulch and control. Soil moisture was monitored for 125 days under which Seredo sorghum variety was planted. A field experiment was set up using a Randomized Complete Block design (RCB), with three blocks each covering an area measuring 10 m by 10 m with replications. The effect of the treatments on moisture retention was monitored using digital YL-69 moisture sensors installed at 20 cm and 40 cm depths respectively. In addition, the crop coefficient and crop water requirement (CWR) were assessed during the crop’s growth period under the different treatments. Normalized Difference Vegetation Index (NDVI) was estimated from growth images obtained from sentinel 2 and then the NDVI used to establish the crop coefficient (Kc). The reference evapotranspiration was determined using the Hargreaves method and the values were then combined with the crop coefficients to obtain the crop water requirement. Results show that Kc values ranged from 0.44 in the initial crop development stage to 0.91 in the mid-season stage and varied with the type of moisture conservation technique. The Kc linearly increased with the increase in NDVI under the different moisture conservation techniques, with a regression coefficient ranging from 0.75 in the combined ridges and mulch to 0.86 in the mulch treatments. The maximum crop water requirement values under each moisture conservation technique were 41.8 mm, 95.1 mm, 177.6 mm and 82.6 mm in the initial development, mid-season and late stages respectively. In addition, the seasonal water requirement of sorghum variety ranged from 386 mm to 395.7 mm. The combined ridges and mulch had the highest water productivity of 2.08 kg/m3 as compared to the ridges, mulch and finally the control which had values of 1.83 kg/m3, 1.66 kg/m3 and 1.45 kg/m3 respectively. The findings from this study are important as they can be used by agriculturalists, farmers and relevant stakeholders in prioritized soil moisture conservation for increased sorghum crop production especially in ASAL areas.