Effect of Tillage Systems and Residue Management on Penetrometer Resistance of Nitisols under Maize Production in Western Ethiopia

Abstract

Penetrometer resistance is one of soil physical properties influenced by tillage systems and crop residue management. Therefore, a field experiment was conducted to determine integrated effects of tillage systems and crop residue management on penetrometer resistance of Nitisols under maize production at five locations in western Ethiopia. Three tillage systems (minimum tillage with residue retention = MTRR, minimum tillage with residue removal = MTRV and conventional tillage = CT) and three N fertilizer levels (69, 92 and 115 N ha-1) were combined in complete factorial arrangement. The experiment was laid out in a randomized complete block design with three replications. The experimental plots were kept permanent for five cropping seasons to observe carry-over effects on soil penetrometer resistance. Tillage systems and depth intervals had significant (P<0.05) influence on penetrometer resistance of Nitisols at all five locations. Maize grain yield was significantly (P<0.05) affected by tillage systems and N application. After five years, penetrometer resistance of Nitisols within 0-15 cm soil layer was higher under MTRR than CT, while MTRV revealed the highest soil strength. Below 15 cm soil layers, the penetrometer resistance of the CT soils tended to be slightly higher than that of the MTRV and MTRR soils. The penetrometer resistance of Nitisols was below the threshold value of 2 MPa at field capacity. Maize grain yield was significantly higher with MTRR, followed by MTRV and CT. The MTRR increased grain yield by 6.6 and 12% as compared to MTRV and CT, respectively. Nitrogen fertilizer application increased grain yield regardless of tillage systems. Application of 92 kg N ha-1 was significantly higher to 69 kg N ha-1, but on par with the 115 kg N ha-1 application, implying 92 kg N ha-1 application could be optimum level for both MTRR and CT systems. Root penetration of maize in the Nitisols could not be impeded by soil penetration resistance after five consecutive years practice of CT, MTRV and MTRR in the study and similar areas.