Abstract
Smallholder agriculture constitutes the main source of livelihood for the Ethiopian rural community. However, soil degradation and uneven distribution of rainfall have threatened agriculture at present. This study is aimed at investigating the impacts of conservation agriculture on irrigation water use, nutrient availability in the root zone, and crop yield under supplementary irrigation. In this study, conservation agriculture (CA), which includes minimum soil disturbance, grass mulch cover, and crop rotation, was practiced and compared with conventional tillage (CT). We used two years’ (2018 and 2019) experimental data under paired-t design in the production of a local variety green pepper (Capsicum annuum L.). The results showed that CA practices significantly (α = 0.05) reduced irrigation water use (13% to 29%) and runoff (29% to 51%) while it increased percolated water in the root zone (27% to 50%) when compared with CT practices under the supplementary irrigation phase. In addition, CA significantly decreased NO3-N in the leachate (14% to 44%) and in the runoff (about 100%), while PO4-P significantly decreased in the leachate (33% to 50%) and in the runoff (16%) when compared with CT. Similarly, CA decreased the NO3-N load in the leachate and in the runoff, while the PO4-P load increased in the leachate but decreased in the runoff. The yield return that was achieved under CA treatment was 30% higher in 2018 and 10% higher in 2019 when compared with the CT. This research improves our understanding of water and nutrient dynamics in green pepper grown under CA and CT. Use of CA provides opportunities to optimize water use by decreasing irrigation water requirements and optimize nutrient use by decreasing nutrient losses through the runoff and leaching.
Highlights
Water and soil nutrients remain the most limiting resources for agriculture
Irrigation water was significantly reduced (p < 0.05) under conservation agriculture (CA) compared to conventional tillage (CT) management
We observed that CA practices increased yields, reduced irrigation water, reduced runoff and the associated NO3-N in the leachate and runoff compared to CT
Summary
Water and soil nutrients remain the most limiting resources for agriculture. rainfed and irrigated agriculture is often hindered by the depletion of soil nutrients through surface runoff and leaching during rainy phases [1,2], as well as by the scarcity of water during dry phases [2,3]. Surface runoff adversely affects the availability of water [3,4,5], soil nutrients [5,6,7], and soil organic matter for plant growth and development [8,9]. Percolated water (leaching) can affect water and nutrient availability to some extent [5]. The nutrient and water components of surface runoff and percolation may deteriorate the water quality of wells, reservoirs, and lakes [11]. The nutrients often removed by water movement and dynamics contribute to water quality deterioration, but this imply an economic loss of soil fertility to the farmer. The current approach of agricultural systems, which promotes the use of more chemical fertilizers [12], for vegetable production, shows a wider expansion of the above risks and is becoming a serious threat to our environment [12,13,14]
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