IMPACT OF SOLE CROPPING AND MULTIPLE CROPPING ON SOIL HUMIFIED CARBON FRACTIONS

Abstract

The present study was planned to improve our understanding how crop rotation can enhance humified C fractions. Along term experiment was conducted on Vanmeter farm of the Ohio State University South Centers at Piketon Ohio, USAfrom 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 fieldconditions. The findings of this long-term study revealed that multiple cropping had significantly improved humified carbonfractions 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 acidassociated glucose (HA-NH and FA-NH) were significantly affected by various crop rotations within five years. The soilunder CC had 22-52% significantly greater NH concentration than CSW and CS rotations respectively. Similarly all croprotations 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 by27– 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, thevalue 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 croprotation 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 croprotation on humified C fractions could be because of variations in type, amount and quality of C returned by different plantsinto the soil. So replacing mono-cropping with multiple cropping can enhance humified C fractions and can improve soilfunctional properties.