Phosphorus Fixing Capacity Of Laterite Soil Blended With Spent Coffee Ground

Abstract

Phosphorus fixation, which is responsible for low availability of P, is one of the major problems of crop growth in acidic soils such as LS. Therefore, the incubation study was conducted to determine the suitability of SCG as soil amender to reduce P fixing capacity of LS. LS samples were collected from three different Karsa areas at depth of 0-15 cm using soil auger and SCG samples were collected from eight coffee houses at Jimma Town. Treatment soils containing 0, 20, 60 and 180 mg/L were prepared from KH2PO4.25 ml portions of the treatment solutions were added to 2 g of LS samples and LS +SCG (2:0.25, 2:0.5, 2:0.75 and 2:1) in cups and were plugged respectively. The samples were incubated at room temperature and allowed to stand for 1, 3, 7, 14 and 28 days respectively. At the set days, the fixed P was determined using of Ascrobic Acid method. The amount of P recovered at different incubation periods increased with increasing a dose of SCG addition. The study revealed the percentage of organic carbon contents in both LS and SCG were as follows: LS (2.106%) < (47.95%). pH of LS (5.61) < pH of SCG (7.21) and available P of LS (41.91 mg/kg) < SCG (1745 mg/kg). The fixed decreased with added a dose of SCG throughout the incubation period in mixture of LS and SCG. The LS blended with SCG showed a less P fixing capacity between 60-66% as compared with LS which shows high P fixing capacity between 92-99%. Less than 63% of P fixation in the mixture of LS and SCG was decreased after one day of incubation. Application of SCG is recommended for LS to increase soil fertility. Organic carbon and available P could therefore be responsible in minimizing of P fixation of LS