Comparative effects of Kraal Manure and Phosporus Fertilizer on Sil acididty and Phosphorus Availability to Maize(zea mays l)
Soil acidity is a major constraint to crop productivity and lime, the primary amendment, is seldom effective when applied alone and it is not easily accessed by resource-poor farmers. Organic residues around the farm are seldom used as soil amendments. This study was conducted at the University of Zambia Farm to determine the comparative effects of kraal manure and phosphorus fertilizer on soil acidity and phosphorus availability to maize. The site is situated at an altitude of 1140 m a.s.l (15˚21`-15˚24` S and 20˚27`-20˚28` E). The soil was classified as mixed, fine-loamy, isohyperthermic Oxic Paleustalf . Treatments comprised of two levels of lime (0t/ha and 3t/ha), three levels of phosphorus (0kgP/ha, 20kgP/ha and 30kg/P/ha and four levels of kraal manure (0t/ha, 2.5t/ha, 5t/ha and 10t/ha).The treatments were replicated three times in a split- split plot design. Lime levels as main plot treatments, four organic amendment levels for Kraal manure as sub plot and three phosphorus levels as sub-subplot treatments. Maize was the test crop. Selected soil chemical properties and plant tissue analysis were determined at the start of the experiment and after crop harvest. Addition of agricultural lime rapidly increased soil pH, concentrations of Ca, Mg and extractable P. Kraal manure additions increased concentrations of Ca and Mg, organic matter and plant available P, but it had a small effect on increasing soil pH (11%). Applied lime increased available P in the soil by unlocking the residual P. The increase in plant available P when kraal manure was applied was expected because the extra P was derived from the kraal manure which contained 1.18% of P. When P fertilizer is applied in combination with lime or kraal manure, the application rates for P would be lower than to when P is applied alone. The increase in grain yield was due to addition of amendments and optimal P fertilizer to ameliorate soil acidity and increase nutrient uptake. Application of 3t/ha lime and 20kgP/ha may be recommended for increasing maize yield on acid soils particularly in the study area. It was concluded that kraal manure alone may be used as amendment to overcome poor soil fertility and increase crop yield on acid soils were lime is expensive and not easily accessed by farmers.