Impact of sole cropping and multiple cropping on soil humified carbon fractions

The present study was planned to improve our understanding how crop rotation can enhance humified c fractions. a long term experiment was conducted on vanmeter farm of the ohio state university south centers at piketon ohio,usa from 2002 to 2007. crop rotation treatments included were continuous corn (cc),corn-soybean (cs) and corn–soybeanwheat- cowpea (csw) rotations. randomized complete block design with 6 replications was used under natural field conditions. the findings of this long-term study revealed that multiple cropping had significantly improved humified carbon fractions compared to mono-cropping system. although total humified carbon (thoc),sugar free humified carbon (hoc) concentration were non-significant however,humin (nh) contents,humic (ha),fulvic acids (fa),humic and fulvic acid associated glucose (ha-nh and fa-nh) were significantly affected by various crop rotations within five years. the soil under cc had 22-52% significantly greater nh concentration than csw and cs rotations respectively. similarly all crop rotations had shown 5–16 increase in ha and 5-17% decreased in fa over time. likewise soil under cc had 16 and 54% greater ha-nh concentration as compared to csw and cs rotations. the fa-nh concentration increased significantly by 27– 51% in soil under all treatments over time. the soil under csw had greater ha/fa (1.6) fallowed by cc (1.4) and cs (1.1). soils under csw had significantly greater ha/hoc (12–18%) as compare to cc and cs respectively. conversely,the value of fa/hoc decreased (1–23%) in soil under all crop rotation treatments within five years. degree of humification (dh) had shown a significant increase (7–12%) in soil under all treatments as compared to 2002. irrespective of crop rotation thoc,hoc,nh,humin,ha,hr and fa/hoc concentration decreased significantly with increase in soil depth. while fulvic acid concentration ha/hoc in all crop rotation increased with increase in soil depth. the effect of crop rotation on humified c fractions could be because of variations in type,amount and quality of c returned by different plants into the soil. so replacing mono-cropping with multiple cropping can enhance humified c fractions and can improve soil functional properties. © 2014,pakistan botanical society. all rights received.