Critical analysis of tillage practices with fertility levels in maize and populations in beans as adaptation measures to climate change to enhance food security at Kabete

Trials were carried out in 2012/2013 short and 2013 long seasons at Kabete site representing a warm and wet environment in Kenya to determine, the appropriateness of combining fertilizer levels for maize and population levels with tied ridges for beans, as adaptation measures under changing climate. The maize experiment consisted of three fertilizer levels of 0, 20 and 40 kg/ha N while the bean experiment had three spacings of 12, 15 and 20 cm in a split plot design. The experiments were replicated thrice and consisted of conventional tillage and tied ridges as main plots representing the two soil water management practices while the three soil fertility levels (in maize N0, N20 and N40) or spacing options (12, 15 and 20cm) were sub plots in a Completely Randomized Block Design. The ridges were tied at intervals of 1 m and spaced at recommended crop spacings (i.e. 75cm for maize and 45cm for beans) and the crop planted on the slope of the ridge in 6 by 5 m plots. Basal phosphate (P205) fertilizer in the form of Triple Superphosphate was applied at planting time at the rate of 40kg/ha. Nitrogen in the form of Calcium Ammonium Nitrate was applied at 20 Kg/ha in the 20 and 40 N treatments at planting and further 20kg/ha N top dressed in the 40 treatment level. Harvesting was done at physiological maturity of grain which was air dried. Statistical analysis was done of the treatments and comparisons done of the adaptation advantages of the treatments. Tied ridging increased maize yields at the medium fertilizer level of 20 (+5.22%) but were negative under both zero (-15.56%) and 40 kg/ha application of fertilizers (-5.42%). In the short season, increased bean spacing from 12 to 20 decreased yields under normal (-13.6%) and tied ridges (-37.3%) but remained higher at populations of 12 and 15. In the long season increasing bean population from spacing of 12 cm to 20 had no advantage and under tied ridging compared to normal tillage. Tied ridging as a climate change adaptive measure should not be instituted as a blanket recommendation across rainfall regimes, crops, fertilization levels or plant populations and is more advantageous in drier seasons