Effect of Conservation Agriculture on Water Retention, Soil Properties and Maize Yields in Semi-Arid Kajiado County, Kenya
Ritei, Leonard Leakey
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Food insecurity and hunger are global challenges attributed to poor crop harvests, land degradation, low soil moisture and declining soil fertility. Low maize yields and household food insecurity in Kajiado, Kenya could be alleviated by use of sustainable agricultural practices such as conservation agriculture (CA), integrated soil fertility management (ISFM) and increased water use efficiency. This study was carried out in Kajiado during the long rainy season of March-July, 2016 to (i) determine the effects of conservation tillage on maize growth and yields (ii) determine the effects of conservation tillage on soil physical properties (soil moisture retention and soil structure) and (iii) determine the effect of conservation tillage on soil chemical properties (Soil Carbon, soil pH, soil N, P, and K). The treatments were laid out in a RCBD with three replications. The treatments included: 1. Conventional tillage with residue removal (Control). 2. Conventional tillage with residue retention (3 ton/ha). 3. Conventional tillage with residue retention (5 ton/ha incorporation). 4. Reduced tillage – (one plough with 3 ton/ha stover incorporation). 5. Reduced tillage – (one plough with 5 ton/ha stover incorporation). 6. No-tillage practice – (no prior tillage, 3 ton/ha stover residue chopped, surface applied). 7. No-tillage practice – (no prior tillage, 5 ton/ha stover residue chopped, surface applied). Analysis was done using SAS version 8. Results from the study show significant effects (p<0.05 and p<0.01) of CA on dry matter maize yields and water retention. The volumetric moisture content at 0-60 cm soil depth was highest in NT5 treatment, followed by NT-3 > RT-5 > CT-5>CT-3 > RT-3 and CTC (Control). At 0-20 cm depth, NT-5 had the highest volumetric soil moisture content of 0.299m3m-3 which was significantly higher than the other treatments. NT-5 increased soil moisture by 9.7%, NT3 by 9%, RT5 by 5.4%, while RT-3 by only 3.8%. After wet sieving, treatments, RT-5, NT-3 and NT-5 significantly increased the 2-1 mm soil aggregate size, thus indicating improvement in aggregate stability of the soils. Up to RT-3 does not degrade the soil structure because there was no significant reduction of the fraction less than 0.5mm. NT-5 significantly gave the highest stover yields of 5334kg/Ha and grain yields of 3228.2kg/ha which was 37.3% increase from the control. CT3 had the highest plant height at (12.5cm) 2 weeks after planting (2WAP). However, NT5 had the highest significant effect (P=0.01) on plant height 4WAP, 6WAP and 8WAP at 58.2 cm, 122.8 cm and 140.2 cm respectively. No significant effects (P<0.01 and P<0.05) were recorded in pH before and after the experiment. However, soil organic carbon (SOC) recorded significant improvements across all the treatments with NT-5 being the highest followed by RT-5 > RT-3 > NT- 3> CT-5 > CT-3 respectively in that order. The treatments had significant effects on soil mineral N (NH4+ and NO3-) and total N. On the other hand, the treatments also had significant effects on available P, Na+, and K+. Therefore, the results confirm that CA is very effective in enhancing crop yields and improving soil physical and chemical properties.