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

In the Mesilla Valley of southern New Mexico, furrow irrigation is the primary source of water for growing onions. As the demand for water increases, there will de increasing competition for this limited resource. Water management will become an essential practice used by farmers. Irrigation efficiency (IE) is an important factor into improving water management but so is economic 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 yield 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 irrigation used by the farmers. The IEs obtained for onion fields irrigated with subsurface drip irrigation methods ranged from 45 to 77%. The 45% represents the nonstnssed treatments, in which an extra amount of irrigation above the evapotranspiration (Et) requirement was applied to keep the base of the onion plates wet. The irrigation water that was not used for Et went to deep drainage water. The return on the investment cost to install a drip system operated at a IE of 45 was 29%. Operating the drip system at a IE of 79% resulted in a yield similar to surface irrigated onions and consequently, it was 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-irrigated onion fields were high because farmers have limited water resources. Consequently, they used the concept of deficit irrigation to irrigate their onion 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 water applied to the field was limited to the amount needed to replace the onions' Et requirements. The maximum IWUE values for onions using the subsurface drip was 0.059 and 0.036 t ha(-1) mm(-1) of water applied for furrow-irrigated onions. The lower IWUE values obtained under subsurfacedrip and furrow irrigation systems compared with sprinkler irrigation was due to excessive 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 suffer from water stress. (C) 2001 Elsevier Science B.V. All rights reserved.