EFFECT OF SURFACE MANAGEMENT PRACTICES ON HYDROLOGICAL RESPONSE AND LAND PRODUCTIVITY UNDER MAIZE-SOYABEAN (Zea mays L.-Glycine max L.) PRODUCTION SYSTEM AT ASSOSA, BENISHANGUL GUMUZ REGIONAL STATE OF ETHIOPIA

Abstract

Soil erosion is a global environmental crisis in the world today that threatens natural environment and also the agriculture where it can be mentioned as more serious in Ethiopia. Thus, site specific soil and water conservation measures study that can easily attain both agricultural and environmental sustainability had been carried out at Assosa. A field experiment was conducted under natural rainfall conditions to investigate the effects of farming systems (soil tillage and cropping systems) on runoff, soil and nutrient losses and yield of both maize and soya bean grows on Nitisol of Assosa area, western Ethiopia. Eighteen experimental runoff plots of 8 m long and 3 m wide each were framed with corrugated iron sheets. The experimental design used was randomized complete block design (RCBD) with six treatment in factorial combinations vis-à-vis three cropping systems (sole maize, sole soya bean and intercropping of maize with soya bean), with tillage system (no tillage and convectional tillage), that were replicated three times. The results revealed non-significant variationamong the treatments regarding their effect on nutrient loss, runoff depth, soil loss, sediment concentration, in situ water conservation and grain yield of maize whereas significant variation were observed for soil loss, bulk density,porosity,void ratio and yield components of soyabean except height of first branch fruiting for soya bean. The treatments had shown non-significant variation for all parameters showing Enrichment ratio of ≥ 1 except some no tillage treatments. Higher enrichment ratios for clay and silt fraction were observed under conventional tillage treatments and thereby high loss of nutrients like nitrogen, available phosphorus, and organic carbon than no tillage treatments. No tillage with soya bean and no tillage with intercropping treatments had shown the value of ≤ 1 for total nitrogen and phosphorus than conventional tillage treatments. No tillage treatments in concomitant with cropping system especially intercropping had retained more nutrients than conventional tillage by reducing runoff and soil loss to Enrichment ratio of ≤ 1. No tillage had reduced sediment concentration per litre of runoff by (3.26 g/L, 3.13 g/L and 4.37 g/L), total runoff volume (by 0.06m3, 0.03m3and 0.06m3per plot and soil loss per hectare by (507 kg/ha, 1300.4 kg/ha and 897.3 kg/ha) as compared to conventional tillage with intercropping, sole maize and sole soya bean cropping systems respectively. Also, No tillage had increased in situ-water retention by 18 mm, 21.3 mm and 14.63 mm per plot as compared to conventional tillage for maize, soya bean and maize-soya bean intercropping systems respectively. Totally, the study ratified the key importance of no tillage for both soil and water conservation than conventional tillage. In cognizant to soil and water conservation, conventional tillage showed the greater result on yield and yield traits than no tillage. Conventional tillage gave the difference of 992 and 694.7kg/ha than no tillage under sole and intercropping of maize respectively. Also, the yield of soya bean has shown the difference of 331.6 and 131.3 kg/ha under conventional tillage for sole and intercropping respectively than no tillage.