Yield and yield components of sorghum, soil chemical properties and nutrient use efficiency as affected by integrated soil fertility, and soil and water management practices in Tharaka-Nithi County

Abstract

Soil fertility depletion due to soil erosion, leaching nutrient leaching and mining, and inappropriate land management by the farmers affects agricultural productivity in the drylands of Tharaka County, Kenya. We sought to evaluate the effects of integrated soil fertility, and soil and water management practices on sorghum yield, soil chemical properties and nutrient use efficiency. A four season field experiment was laid in randomized complete block design with twelve treatments replicated four times. The treatments include manure plus fertilizer plus tied ridging under high (120 kg ha^-1), moderate (60 kg ha^-1) and low (30 kg ha^-1) N application rates; manure plus fertilizer plus minimum tillage with crop residue mulch under high, moderate and low N application rates; manure plus fertilizer under conventional tillage with high, moderate and low N application rates; Managing Beneficial Interactions in Legume Intercrops (MBILI) with moderate rate of N application; MBILI (No fertilization) and the control. Soil samples were collected at the beginning and the end of the study at 0-15 cm depth for chemical analysis. Laboratory and field analysis for various soil properties was conducted following the standard procedures. Yield and above ground biomass were determined at every harvesting while other crop growth parameters taken periodically during the season. Student T-test was used for pairwise comparison of soil chemical properties before and after the experiment at p < 0.05. Yield and above ground data were subjected to ANOVA and Tukey’s honestly significant difference test used for mean separation at p < 0.05 where there were significant differences in SAS 9.4. Treatments in did not significantly improve Soil pH, organic carbon and N, while P improved under all the treatments after the four seasons. Soil micro-nutrients also improved by the treatments. Use of animal manure plus mineral fertilizer under high, moderate and low rates in combination with minimum tillage with mulch, tied ridges and conventional tillage, and MBILI intercrop improved sorghum grain and stover yield, crop growth parameters and nitrogen use efficiency in varying capacities. However, treatments with high fertility rate had lowest nutrient use efficiency across the season despite having the highest yield and crop growth parameters. Ideal fertilization rate that improves productivity and economically sustainable is therefore moderate fertilizer application. This necessitate the need of assessing of thee high fertilization rate before recommendation.