White Lupin (Lupinus albus L. cv. Amiga) Increases Solubility of Minjingu Phosphate Rock, Phosphorus Balances and Maize Yields in Njoro Kenya

Joyce J Lelei,Richard N Onwonga

doi:10.5539/sar.v3n3p37

Joyce J Lelei, Richard N Onwonga

Open Access

https://doi.org/10.5539/sar.v3n3p37

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Abstract

Exudation of high amounts of citrate in white lupin (Lupinus albus L. cv. Amiga) has the advantage of being effective in mobilization of a wide range of sparingly soluble P sources. To improve cultivation system of maize, a field experiment was conducted to assess effectiveness of white lupin (Lupinus albus L. cv. Amiga) in increasing solubility of minjingu phosphate rock (MPR), phosphorus balances and maize yields in Njoro sub-County, Kenya. The randomized complete block design experiment was conducted for four seasons; short (October – February) and long rain seasons (March-September) of 2010 and 2011. The treatments were; (i) fallow (F) – maize (M) rotation with triple superphosphate (TSP) applied (MTSP- F), (ii) fallow - maize rotation with MPR applied (MMPR –F), (iii) lupin (L) – maize rotation with MPR applied (MMPR- L) and (iv) maize/lupin intercrop with MPR applied (M/LMPR – F). Soil and plant P and maize grain yield were higher in M/LMPR – F (with additional lupin grain yield) and MTSP– F treatments. All treatments resulted in positive P balances at the end of two years with highest values in MTSP– F treatment and lowest in M/LMPR – F. Intercropping lupin with maize amid application of MPR is recommended for enhanced maize performance in the farming systems of resource poor farmers. Measurement of available soil nitrogen and comparison of lupin with other legumes in solubilizing MPR is recommended.

Highlights

Phosphorus (P) is an essential macronutrient for plant growth and its availability is often the limiting factor for crop cultivation (Marschner, 1995)
In the seasons; long (LRS) and short (SRS) of 2010 soil available P was significantly (P < 0.05) higher in maize rotation with MPR applied (MMPR- L) and M/LMPR – F treatments at the seedling stage while at 50% flowering and maturity, levels of available P in the soil were significantly higher in the MMPR– L treatment
Higher yields in M/LMPR – F treatment was due to increased mobilization of P by lupin which subsequently increased maize yields

Summary

Introduction

Phosphorus (P) is an essential macronutrient for plant growth and its availability is often the limiting factor for crop cultivation (Marschner, 1995). To address soil fertility problems associated with depletion of phosphorus, minjingu phosphate rock (MPR) is an affordable alternative (Onwonga et al, 2013). It is the predominant type of phosphate rock (PR) deposit in Eastern Africa with sufficient quantity and reactivity cum potential for direct application (Okalebo et al, 2007). The PRs are natural minerals requiring minimum processing, mainly involving grinding, are environmentally friendly and could be more efficient than the soluble fertilizers in terms of recovery of phosphate by plants (Schultz, 1992; Yeates & Clarke, 1993; Rajan et al, 1994)

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