Enhancing soil fertility through intercropping,inoculation and fertilizer

The present study was conducted to investigate the effects of intercropping grass (panicum maximum) and legumes (vicia sativa and cowpeas) alone or coupled with inoculation or fertilizer on soil fertility. the study comprised of two field experiments conducted under rain fed conditions for two years (june,2005 to september,2007) at national agriculture research centre,islamabad,pakistan. in one experiment intercropping (33,50 and 67%) of grass and legumes alone as well as coupled with seed inoculation were studied while,same set of treatments was combined with fertilizer application at the rates of 25,75 and 50 kg/ha (n,p 2o5 and k 2o) in the second experiment. total soil n increased by 0.008% due to symbiotic fixation in addition to plant uptake under best treatment when compared with grass alone while,soil organic matter increased by 0.19%. after crop harvest soil n content was determined to be higher in all the treatments of the experiment compared with growing grass alone. legumes caused rhizobial n fixation that caused an increase in soil n. similarly,intercropping and inoculation increased this soil characteristic that was found to be non-significant in the first crop but later on became significant,especially when intercropping of grass with legumes after seed inoculation was investigated or fertilizer was supplemented to the crops. thus,not only grass used the symbiotically fixed n by companion legumes but also enhanced the soil n content. the effect of fertilizer was not measurable statistically in case of soil organic matter. this parameter,in general,was not affected significantly when assessed after first crop harvest. nevertheless,legumes alone or intercropped within grass increased this important soil constituent. inoculation proved further beneficial in this regard but combination of intercropping (especially 67%) either with seed inoculation or application of fertilizer was found as the best technique for increasing soil organic matter.