TILLAGE, GRASS MULCH AND INTEGRATED NUTRIENT MANAGEMENT EFFECT ON SELECTED SOIL CHEMICAL PROPERTIES, YIELD AND YIELD ATTRIBUTES OF SORGHUM (Sorghum bicholar L. Moench) IN ASSOSA DISTRICT, WESTERN ETHIOPIA

Abstract

Tillage in general and conservation tillage in particular is a crop production system that retains an everlasting soil cover through preservation of crop residues on soil surface with zero and reduced till to enhance natural biological processes. Sustainable soil and crop management practices that reduce soil erosion and nitrogen (N) leaching, conserve soil organic matter, and optimize sorghum yields remain a challenge particularly in western part of Ethiopia. Towards addressing this problem, four field experiments were carried out in the acidic soil of Assosa, western Ethiopia, for two years 2020 and 2021 growing seasons. The first experiment was conducted with the objective to ascertain the effect of integrated application of tillage methods (conventional, minimum and zero) and grass mulching (0, 2.5, 5, 7.5, and 10 ton ha-1 ) on soil chemical properties, yield and yield attributes of sorghum. The second experiment was conducted with the objective to identify the effect of integrated application of grass mulching (0, 2.5, 5 and 7.5 ton ha-1 ) and inorganic fertilizers (0, 50, 100 and 150%P) + 46 kg N ha-1 on productivity of sorghum and subsequent changes on chemical properties of the soil. The third experiment was conducted with the objective to assess the effect of integrated application of tillage methods and cattle manure (0, 5, 10, 15 and 20 ton ha-1 ) on soil chemical properties, yield and yield attributes of sorghum. Finally, the fourth experiment was conducted with the objective to assess the effect of integrated application of cattle manure (0, 5, 10, and 15 ton ha−1) and inorganic fertilizers (0, 50, 100 and 150%NPS) + 46 kg N ha-1 on productivity of sorghum and subsequent changes on chemical properties of the soil. All experiments were laid out in randomized complete block design with three replications. The ANOVA of the first experiment showed CEC significantly (P<0.05) affected by the main effect of year, tillage method and grass mulch; whereas, soil OC significantly (P<0.01) influenced by the three way factors and also soil pH, OC, TN, P and S significantly (P<0.05) influenced by the three way factors(Y, TM and GM). Number of heads significantly (P<0.05) affected by the combined factors of tillage and grass xx mulch, whereas LAI and TSW significant (P<0.05) influenced by three way factors. Grain yield, biological yield and HI were significantly (P<0.05) affected by the two way factors (TM and GM). The ANOVA of the second experiment showed TN and available S significantly (P<0.01) influenced by the three way factors, while soil pH, organic carbon, available P, and CEC significantly (P<0.05) influenced by the three way factors(Y, GM and IF).Number of tillers significantly (P<0.05) affected by the three way factors; while, number of heads (NH), LAI and TSW of sorghum was significantly (P<0.01) influenced by the three way interaction (Y x GM x IF). The three way interactions of Y x GM x IF showed significant (P<0.01) influences only on grain yield, while significant (P<0.05) influences on BY and HI of sorghum. The ANOVA of the third experiment showed that the three way interactions (Y x TM x CM) significantly (P<0.01) influenced soil organic carbon, while significantly (P<0.05) influenced soil pH TN, available P, available S and CEC of the soil. Number tillers and number of heads significantly (P<0.05) affected by the two way factors (TM and CM), while LAI and TSW significantly (P<0.05) influenced by the three way interactions (Y, CM and TM). The three way interactions of Y, CM and TM significantly (P<0.01) influences the biological yield, while significantly (P<0.05) influences GY and HI of sorghum. In the fourth experiment, all those selected soil chemical properties were significantly (P<0.05) affected by the three way interactions of Y, CM and IF. Number of tillers, heads and leaf area index significantly (P<0.05) affected by three way interactions (Y, CM and IF), while TSW significantly (P<0.01) affected by three way interactions (Y, CM and IF). Grain yield highly significantly (P<0.001) affected by the three way interactions of Y, CM and IF, while biological yield and HI significantly (P<0.01) affected by the three way interactions of Y, CM and IF. All those soil chemical properties, yield attributes and yields of sorghum were improved from the first experiment to third year and fourth, but decline observed in the second experiment. However, the integrated use of cattle manure and inorganic fertilizers has shown the best improvement on SOC, TN, available P, available S and CEC in the fourth experiments. In general, there was a grain yield increment from the first (0.82 t ha-1 ) to the third (2.02 t ha-1 ) to the second (3.16 t ha-1 ) and then to fourth (3.98 t ha-1 ) objectives Therefore, integrated application of 10 t ha-1 cattle manure and 150% NPS ha-1 with 46 kg N ha-1 could be best to enhances of soil chemical properties and yields of sorghum in the study area.