Rotation system

Abstract: In order to calculate the actual erosion according to the universal soil loss equation (USLE) and to estimate the impact of land use on soil erosion it is important to know the C-factor. Based on the USLE crop-growth stages, the cover-management C-factors were calculated for the main crop rotation systems on arable farms in Belgium with particular reference to those occurring on 40 farms on silt and silt loam soils in the Kemmelbeek watershed, West-Flanders, Belgium. The different rotation systems were composed of the following crops: sugar beet (SB), winter wheat (WW), potato (PO), maize (M), beans (B), winter barley (WB), peas (PE), chicory (CH), leek (L), carrot (CA), celeriac (CE), rye grass (RG) and temporal grassland (TG). The erosivity factor R during the rotation was calculated on the basis of a detailed rainfall time series over a time period of 27 years. The crop data (development of cover, sowing and harvesting date, amount of residue) were collected from literature and personal communications. For most rotation systems the C-factors were between 0.28 and 0.38. High C-factor values were obtained with M/M/M/PO (C=0.47), and with CE/L/PO (C=0.51). Remarkable small C-values (C=0.24–0.27) were found when winter cereals (WW and WB) were put in the rotation scheme. Whether or not the foliage of the sugar beets was removed, had no effect on the C-factor. The effect of green manuring on the C-factor in some rotation schemes was smaller than could be expected. The C-factor was also affected by the position of the crop in the rotation scheme. The calculated C-factors indicated that the application of some rotation systems might cause more erosion by runoff. Therefore, these calculated C-factors can be used as a criterion to select an appropriate rotation system to reduce erosion risk on site. However, validation of these values using experimental field plot data is still required.

Abstract: Development and utilization of cropping systems in rainfed areas are highly dependent on their water use efklciencies, especially in subhumid areas. The objective was to evaluate the effect of crop rotation and N fertilizer rates on precipitation use efficiency by dryland corn (L.). Corn was grown under rainfed conditions at Mead, NE, on a Sharpsburg silty clay loam (fine, montmorillonitic, mesic Typic Argiudoll) in four cropping systems: (i) continuous corn, (ii) a 2-yr soybean [ (L.) Merr.]-corn rotation, (iii) a 4-yr rotation of oat [ (L.)] + clover [80% Lam. and 20% L.]-grain sorghum [ (L.) Moench]-soybean-corn, and (iv) a 4-yr rotation of soybean-grain sorghum-oat + clover-corn. Nitrogen fertilizer rates used for corn were 0, 90, and 180 kg N ha as NHNO. Corn grain precipitation use efficiency was significantly affected by year, rotation, and N fertilizer rates from 1984 through 1991. Precipitation use efficiency ranged from 36 to 137 kg ha cm for continuous corn and from 57 to 165 kg ha cm for corn grown in rotation from 1984 through 1991. Precipitation use efficiency was greater in rotation (101.8 kg ha cm) than in continuous corn (83.6 kg ha cm). In dryland production areas, cropping systems with greater and more stable precipitation use efficiency can reduce crop failures.