Interactive effects of lime, manure, N and P fertilizers on maize (Zea mays L.) yield and N and P uptake in an acid mollic Andosol of Molo Kenya
Mochoge, B. O.
Lelei, Joyce J.
Onwonga, Richard N.
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Maize production in Molo division, situated in the central Rift Valley is constrained by acid soil infertility and high P fixation. To realize maximum crop production, the acid infertile soil may be corrected through liming, use of organic manure or high application rates of P and N fertilizers. Use of high N and P fertilizer doses is however unviable to small-scale farmers. It was thus hypothesized that use of lime, manure, urea and TSP in combination would improve the immediate availability of N and P to crops and consequently boost maize yield. The study was conducted at the Kenya Agricultural Research Institute (KARI) farm, Molo. A randomized complete block design (RCBD) with a 23 factorial arrangement was used. Lime (L), manure (M), and urea/TSP (NP) ferti1izers each at two levels; 0 (as the first level for all treatments) and 2.5 t ha-1, 5 t ha-1, and 50/75 kg ha-1, respectively as the second level, were the factors. The NP fertilizers and manure treatments gave significant increases in maize grain and DM yields. L*M*NP interaction gave the highest grain (4387 kg ha-1) and DM (7410 kg ha-1) yields. The lowest grain (3067 and 3158 kg ha-1) and DM (5250 and 5300 kg ha-1) yields were obtained in the control and lime treatments, respectively. Plant N and P uptake was significantly higher in L*M*NP, NP, L*NP and M*NP interactions and M treatment. In a para1lel study the effect of lime on P availability and consequently maize yield was investigated using a RCBD. The treatments were 2.5 t ha-1 of lime (blanket application) and four rates of TSP (0, 25, 50 and 75 kg ha-1). Liming did not reduce P application rates as higher P rates combined with liming gave significantly better grain and stover yields than the lower (0 and 25 kg ha-1) rates. The results of this study show that to enhance maize production and available N and P in the acid soil, application of manure (5t ha-1) two weeks before planting and/or TSP (75 kg ha-1) at planting and urea (50 kg ha-1) as a top dress a month after planting is necessary. Key words: Acidity, andosol, interactions, Kenya, lime, manure, TSP, ure