Soil Fertility as Influenced by Phosphorus Management in Preceding Lucerne under Lucerne-fodder Sorghum Cropping System

摘要

The N, P, K and S uptake by lucerne was significantly higher under 75 kg P2O5 ha"1 from SSP with VAM. The single super phosphate recorded higher N, P, K and S uptake than rock phosphate. VAM inoculated lucerne plants removed more N, P, K and S over their same level of P uninoculated plants irrespective of P sources except higher levels of P. The highest N and K uptake by fodder sorghum were recorded under the residual effect of 75 kg P2O5 ha~(-1) from SSP with VAM, while the highest P uptake was recorded with 500 and 250 kg RP ha~(-1) with VAM and the highest S uptake was observed under 750 kg RP ha1 with VAM and 75 kg P2O5 ha1 from SSP with VAM during 2007 and 2008, respectively. Hundred percent (100 %) recommended dose of fertilisers (RDF) recorded significantly higher nutrients uptake than 50 % RDF. Soil available N, P and S showed negative balance after two years of fallow-fodder sorghum, whereas it was positive under lucerne-fodder sorghum cropping system. Soil available K showed negative balance after two years of both fallow-fodder sorghum and lucerne-fodder sorghum cropping system. The soil available N, P and S showed positive balance under both fertiliser levels after two years of lucerne-fodder sorghum cropping system and increased from 50 to 100 % RDF. The soil available K showed negative balance and higher under 50 % RDF.