Impacts of conservation agriculture-based farming systems on optimizing seasonal rainfall partitioning and productivity on vertisols in the Ethiopian drylands uri icon

abstract

  • Field water conservation practices are a way to build resilience against drought by increasing productive green water through reducing runoff and evaporation and thereby boosting crop yield. A field study was undertaken on permanently kept rainfed experimental plots established in 2005 on a vertisol in order to evaluate two resource saving cropping systems based on conservation agriculture (CA) that integrate in situ soil and water conservation tillage practices (derdero+ and terwah+) as compared to a conventional system in terms of soil moisture, runoff, water loss (drainage and evapotranspiration together), water productivity and crop yield. The experimental layout was a randomized complete block design with three replications and a plot size of 5 m x 19 m. The farming systems differed in tillage practice, but all had wheat, teff, barley and grass pea crops grown in rotation. The tillage treatments were (i) derdero+ (DER+) with a furrow and permanent raised bed planting system, plowed only by refreshing the furrow once at planting with no tillage on top of the permanently kept raised beds, 30% standing crop straw retention, and with,similar to 20% of the crop residue being covered with soil during refreshing the furrow at planting, (ii) terwah+ (TER+) with furrows made at 1.5 m intervals, plowed once at planting, 30% standing crop straw retention and fresh broad beds, and crop residue being partly covered with soil during tillage at planting, and (iii) conventional tillage (CT) with a minimum of three plain tillage operations and complete removal of crop straw. All plowing as well as the maintenance of the furrows of the permanent raised beds was done using a local ard plow called mahresha. Glyphosate was sprayed at 2l ha(-1) to control weeds before crop emergence, starting from 2007 with DER+ and TER+. Runoff was collected at the lower end of each plot in calibrated runoff collectors after each runoff event. Soil water content was measured using the gravimetric method at 5-6 day intervals. Normalized Difference Vegetation Index (NDVI) was measured in the field at several phenological stages, using a handheld GreenSeeker (TM) Optical Sensor Unit. Soil water storage (0-80 cm soil depth) during the growing season was always highest with DER+ followed by TER+ and CT, whereas the opposite trend was observed for runoff. On the other hand, deep drainage and evapotranspiration was always highest in the DER+ compared to CT. NDVI records throughout the growing season were significantly highest with DER+ for wheat and grass pea, while the highest values were observed with TER+ when under teff. These values were directly proportional to the above ground crop biomass and yield. The grain and straw yield of wheat in 2009 was increased from 1.6 and 3.7 t ha(-1) with CT to 2.6 and 5.2 t ha(-1) with DER+, respectively. Our study demonstrates that field water conservation tillage practices that incorporate CA principles are effectively increasing green water in the root zone available for crops and thus, improve crop productivity and yields substantially on vertisols in drylands without other inputs. (C) 2014 Elsevier B.V. All rights reserved.

publication date

  • 2015
  • 2015