THE EFFECT OF IMPROVED SOLUBILITY AND UPTAKE OF LIME BY THE USE OF TRIPLE SUPER PHOSPHATE FERTILIZER AND SLUDGE ON CROP PRODUCTION

Abstract

Soil acidity is one of the major problems that limit agricultural productivity. Improving fertilizer uptake is a key issue to sustainability of crop production. Fertilizer efficiency by most crops and farming systems is still very poor. Calcium carbonate, the chief component of limestone, is widely used for amendment of soil acidity and to supply calcium for plant nutrition. Since agricultural lime is more soluble in acid soils than in neutral or alkaline soils, its solubility can be improved in acidic conditions, using triple superphosphate (TSP) fertilizer which has a pH of 2.47 and therefore when used with sludge can improve lime uptake. This study aimed finding how crop production can be improved using TSP, lime and sludge, and the research was conducted at the University of Eldoret over a period of two seasons, 2006 and 2007 during long rains. Treatment combinations were; control, lime + sludge, TSP + lime, TSP + sludge, TSP + sludge +lime. Randomized complete block design was adopted with treatments being replicated twice in each block. The test crops used were; maize (H614), wheat (Mwamba), beans (Rose coco). The treatments were replicated two times and applied in plots measuring 4 m x 4 m. planting was done in early May after onset of long rains. Lime was applied in plots one week before planting the crops at 1.5 tons per hectare. Nitrogen was applied one month after planting the crops. All crops were harvested after reaching full maturity. Data collected included laboratory solubility test data for the fertilizer material formed from combinations of lime, TSP and sludge. All samples (lime, TSP and sludge) were mixed in different proportions and their pH and phosphorous content analyzed. Soil available P was determined by Olsen method while total soil nitrogen was done using the Kjedahl method. Measurement of pH was done using glass electrode meter and water as a reagent. In addition; grain yield and stover biomass measurements were taken. Analysis of variance and mean separation were done on the grain yields and stover biomass to establish best treatment combinations. All fertilizer treatment combinations‟ effect on grain yield and biomass were statistically different form each other (p<.001). The combination of (TSP + lime + sludge) gave highest grain yields and stover biomass in maize of over 21 kg and 45 kg, respectively. The combination of TSP and lime produced highest grain yield and biomass in wheat and beans. There was no significant difference between a combination of (TSP + lime) and (TSP + lime + sludge) on wheat grain yields. The combination of (lime + sludge) gave the lowest yields for both grain and stover biomass for the 3 crops. There was, however, no significant difference in production (both grain and biomass) of the 3 crops for different growing seasons or years (p<.367). It is recommended that the combination of (TSP + lime + sludge) should be used in maize production while (TSP and lime) production of wheat and beans as this will increase productivity by improving soil fertility and health of the crops