An analysis of soil organic matter dynamics in relation to management, erosion and yield of wheat in long-term crop rotation plots

We examined the influence of management on soil organic matter (SOM) dynamics and yield of wheat grain in semiarid Chernozemic and humid Gray Luvisolic soils. The Century model was tested with data obtained from long-term research plots cropped to wheat (Triticum aestivum L.) monoculture and cereal-hay (CH). Century simulated changes in soil organic-C (DC) and organic-N (ON) within 10% of actual measurements taken over decades. Our analysis indicated that management and soil erosion affected the rime required for SOM to achieve new steady-state level (T-st). T-st ranged between 12 yr under wheat and 46 yr under CH cropping. Increasing the SOM content of degraded soils to new steady-state level appears to increase grain yield between 86 kg ha(-1) and 840 kg ha(-1). Wheat-fallow (WF) rotation plots receiving <10 kg N ha(-1) yr(-1), and with erosion >13.6 t ha(-1) yr(-1) degraded SOM. The average long-term yield of wheat grain (including new high yielding varieties) was maintained at < 910 kg ha(-1) yr(-1) under degraded SOM content. Well-fertilized continuous wheat (CW) and CH rotation plots with erosion <4 t ha(-1) yr(-1) aggraded SOM content, and maintained the long-term average grain yield at >1290 kg ha(-1) yr(-1). Sustained OC levels were attained by returning 1030 kg C ha(-1) yr(-1) as plant residue (roots + aboveground) and keeping soil erosion less than or equal to 12.8 t ha(-1) yr(-1). Sustainable crop production systems need to consider SOM dynamics and erosion as factors limiting grain yield even after introducing genetically improved wheat varieties.