Evaluation of Soil Fertility Status and Potato (Solanum Tuberosum L.) Response to Fertilizers in Central Kenya Highland

Abstract

Increasing the low potato productivity due to declining soil fertility in Kenya requires an understanding of fertility status and potato response to site-specific fertilizer formulations. This study was conducted in central Kenya highland; Meru and Nyandarua regions with the objectives as follows: i) identify limiting nutrients to potato production ii) determine response to the addition of the limiting nutrients, and iii) evaluate the effect of potato fertilizer blend(s) on yield of the potato crop. Soil and potato nutrient content were determined using inductively coupled plasmaoptical emission spectrometry (ICP-OES) procedures and grouped into adequacy levels. Leaf area index (LAI) and aboveground biomass were determined during flowering and tuber bulking growth stages from the experimental trial. Tuber yields were determined during the bulking stage and at full maturity. Harvest index and nutrient use efficiency were estimated for the experimental trials. Cluster and factor analyses were performed on survey data while generalized linear models were used for data from the field trials using R software version 2.2.3. Means were separated using Tukey’s Honest Significant Difference (HSD) at (p ≤ 0.05). Pearson correlation and linear regression analyses were applied to determine the relationship between the measured variables. Soils from both Meru and Nyandarua with nutrient contents below critical levels constituted 66% and 20% for N, 46% and 85% for P, 67% and 31% for S, 9% and 51% for Cu, and 87% and 80% for B respectively. Subsequently, low tissue nutrient concentrations were observed for N, P, K, and S elements. A reduction in potato yields was observed when specific nutrients were omitted as follows; 9 t ha-1 when N was omitted and 3 t ha-1 when P was omitted. DAP fertilizer exerted the most significant effect on potato haulm (16 g plant-1) on the variety Sherekea. The effect was also observed on potato yield in which 29.2 t ha-1 was recorded with DAP, and a yield of 26.6 t ha-1 with the application of new Mavuno on variety Sherekea. A significant positive interaction (P <0.05) between fertilizer type and soil type was observed. Fertilizers had a significant effect on the agronomic efficiency of N (AEN), P (AEP), and K (AEK). These results show that N, P, K, S and B are the nutrients limiting potato productivity in central Kenya and their fortification would depend on specific soil nutrient requirements and associated applications.