Comparison of sprinkler, trickle and furrow irrigation efficiencies for onion production

In the Mesilla Valley of southern New Mexico, furrow irrigation is the prim ary source of water for growing onions. As the demand for water increases, there will de increasing competition for this limited resource. Water manag ement will become an essential practice used by farmers. Irrigation efficie ncy (IE) is an important factor into improving water management but so is e conomic return. Therefore, our objectives were to determine the irrigation efficiency, irrigation water use efficiency (TWUE) and water use efficiency (WUE), under sprinkler, furrow, and drip irrigated onions for different yi eld potential levels and to determine the IE associated with the amount of water application for a sprinkler and drip irrigation systems that had the highest economic return. Maximum IE (100%) and economic return were obtained with a sprinkler system at New Mexico State University's Agriculture Science Center at Farmington, NM. This IE compared with the 54-80% obtained with the sprinkler irrigatio n used by the farmers. The IEs obtained for onion fields irrigated with sub surface drip irrigation methods ranged from 45 to 77%. The 45% represents t he nonstnssed treatments, in which an extra amount of irrigation above the evapotranspiration (Et) requirement was applied to keep the base of the oni on plates wet. The irrigation water that was not used for Et went to deep d rainage water. The return on the investment cost to install a drip system o perated at a IE of 45 was 29%. Operating the drip system at a IE of 79% res ulted in a yield similar to surface irrigated onions and consequently, it w as not economical to install a drip system. The IEs at the furrow-irrigated onion fields ranged from 79 to 82%. However, the Ifs at the furrow-irrigat ed onion fields were high because farmers have limited water resources. Con sequently, they used the concept of deficit irrigation to irrigate their on ion crops, resulting in lower yields. The maximum IWUE (0.084 t ha(-1) mm(- 1) of water applied) was obtained using the sprinkler system, in which wate r applied to the field was limited to the amount needed to replace the onio ns' Et requirements. The maximum IWUE values for onions using the subsurfac e drip was 0.059 and 0.036 t ha(-1) mm(-1) of water applied for furrow-irri gated onions. The lower IWUE values obtained under subsurfacedrip and furro w irrigation systems compared with sprinkler irrigation was due to excessiv e irrigation under subsurface drip and higher evaporation rates from fields using furrow irrigation. The maximum WUE for onions was 0.009 t ha(-1) mm( -1) of Et. In addition, WUE values are reduced by allowing the onions to su ffer from water stress. (C) 2001 Elsevier Science B.V. All rights reserved.