Abstract:
Land degradation in the form of soil erosion is a serious global problem. To sustain land productivity, besides the commonly adopted crop rotation practices, level soil bunds have been implemented. However, their effectiveness has not been reflected yet in the study area. The objective of this study was to investigate the three year cumulative effect of crop rotation and conservation practice on selected soil physico-chemical properties in Northwestern part of Ethiopia. Soil samples (0-20 cm depth) were collected from seven crop rotation practices with conservation practice and adjacent fields without any conservation measure in three replications. A total of forty two composite samples were used for analysis by using SAS software. The soil parameters bulk density, texture, soil organic matter, total nitrogen, pH, exchangeable acidity, exchangeable bases, cation exchange capacity, available phosphorus, available potassium and C:N ratio were analyzed. The land rotated with maize-wheat-faba bean exhibited significantly higher mean bulk density (1.06g/cm3) than the other crop rotation (i.e ranged from 1.02-1.04g/cm3). All the values of bulk density were below the critical values for agricultural use (1.4 g/cm). The analysis of variance revealed there was significant (p<0.05) effects of crop rotation and conservation practice in all studied soil properties. Mean values of pH (5.34, 4.98 and 5.4), Ex. acidity (2.03, 2.53 and 2.16cmolc/kg ), Soil OM (4.53%, 5.12% and 5.02%), CEC (45.17, 48.03 and 49.47cmolc/kg ), TN (0.23, 0.25 and 0.27%), Av.P (10.21, 7.23 and7.95ppm) and C:N ratio (11.18, 11.95 and 10.8) were recorded under rotations with continuous maize, maize-pepper-pepper and maize-faba bean-pepper respectively. Mean values of pH (5.34 and 4.97), Av.P (9.51 and 6.53ppm), CEC (48.3 and 46.87cmolc/kg) and Ex. acidity (2.5 and 2.85cmolc/kg) were also recorded under conserved and un-conserved farmlands respectively. Considering the interaction effect of crop rotations by conservation practice, all studied parameters except bulk density, CEC and C: N ratio, were significantly (p<0.05) affected. High value of pH (5.6) was recorded under maize-maize-maize and maize-wheat-faba bean rotations plus conservation practice. Maize-wheat-maize, maize-maize-maize and maize-wheat-pepper plus conservation practice showed low value of exchangeable acidity 1.71, 1.81 and 1.81cmolc/kg respectively. The findings indicate more diverse crop rotations, growing of grain legume and constructions of soil bund were the best option to improve most soil properties. A critical study on such type of issue should be carried out over a longer period of time in order to announce detail understanding about cropping system to the community.
