Effect of soil amendments on availability of soil phosphorus and uptake by maize in Vihiga County, western Kenya

Abstract

The combined use of organic inputs and fertilizers as promoted via Integrated Soil Fertility Management (ISFM) approach may have a significant effect on bioavailability of phosphorus (P) and enhance its uptake by crops. To assess this, a field study was conducted to determine the effects of combined use of lime, NPK fertilizer, farmyard manure (FYM) and Zinc (Zn) on short-term changes in available soil P. This was followed by determination of P uptake in the stover and the maize grain. Thus, four field experiments were established in four sites in Vihiga County, western Kenya; two sites (Gurugwa 1 and 2) in Sabatia sub-county and two (Bumuyange and Jivogoli) in Hamisi sub-county during the long rain (LR) and short rain (SR) seasons of 2015. The treatments comprised of (i) an absolute control, (ii) NPK (100 kg N ha-1, 30 kg P ha-1 , 42 kg K ha-1 ), (iii) NPK + FYM (2 t ha-1), (iv) NPK + FYM (2 t ha-1) + Lime (2 t ha-1) + Zn (3 kg ha-1), (v) NPK + FYM (3 t ha-1), (vi) NPK + FYM (4 t ha-1) and (vii) NPK + Lime (2 t ha-1) + Zn (3 kg ha-1). Each of these treatments were replicated three times and randomly allocated within each replicate. Soils were sampled at 0, 42, 86 and at 120 days after planting and analyzed for available P content. Results showed that combined use of NPK fertilizer, FYM, lime and Zn (treatment iv) gave significantly larger (P<0.05) available P levels after 42, 86 and 120 DAP (Days after planting) relative to the control. In the maize ear leaf, the largest total P content were observed in all treatments containing FYM. In the maize grain, again, the treatment (iv) resulted in the largest P content. Further, use of NPK fertilizer with FYM at 3 t ha-1 and 4 t ha-1 resulted in significantly larger (P<0.05) P content in the maize stover. By embracing ISFM strategies, low P uptake at farm level may be alleviated. Locally adapted fertilizer packages and amendment blends aimed at addressing specific limiting soil conditions such as Zinc deficiencies can further enhance P uptake in maize.