Yield and water use efficiency of cowpea under water deficit

ABSTRACT The state of Pará is the main regional producer of cowpea, but its yield is still low compared to other states of the Northern region such as Amazonas and Tocantins, due to the management adopted and the water regime during the cycle, since its cultivation is conducted on a rainfed basis. The objective of this study was to evaluate how water deficit imposed during reproductive stage interferes in the yield of cowpea and in its water use efficiency under the climatic conditions of Castanhal, Pará, Brazil, for agricultural planning purposes. The experiment was carried out in Castanhal, northeastern region of the Pará state during the dry season of 2014, 2015 and 2016. The experimental design was randomized blocks with six blocks and four treatments, corresponding to different irrigation depths in the reproductive stage, defined as 100, 50, 25 and 0% of the crop evapotranspiration. Water use efficiency (WUE) was determined by the ratio between total grain yield and total water used in each treatment. Maximum water availability led to an average increase in yield of 58% compared to the treatment without irrigation. Water depths below 260 mm limited yield to values lower than 1,000 kg ha-1. The cultivar adopted had WUE of 4.63 kg ha-1 mm-1, in response to the higher levels of water supply, but showed WUE of 4.31 kg ha-1 mm-1 under water depth of 50% of water demand.

摘要 帕拉州（Pará）是巴西主要的区域豇豆（cowpea）产区，但相较于北部地区的亚马逊州（Amazonas）、托坎廷斯州（Tocantins）等其他州，其豇豆产量仍偏低，这主要受制于所采用的种植管理方式及生育期内的水分状况——当地豇豆种植均为雨养模式。本研究旨在评估巴西帕拉州卡斯塔纳尔（Castanhal）的气候条件下，生殖阶段施加的水分亏缺对豇豆产量及水分利用效率（WUE）的影响，以期为农业规划提供参考。本试验于2014、2015及2016年旱季在帕拉州东北部的卡斯塔纳尔开展，试验采用随机区组设计，设置6个区组与4个处理，分别对应生殖阶段不同的灌溉定额，即作物蒸发蒸腾量（crop evapotranspiration）的100%、50%、25%和0%。水分利用效率（WUE）通过各处理下籽粒总产量与总用水量的比值计算得到。结果表明，与无灌溉处理相比，充分供水可使产量平均提升58%；当灌溉定额低于260 mm时，产量被限制在1000 kg·ha⁻¹以下。供试品种在高供水水平下的水分利用效率为4.63 kg·ha⁻¹·mm⁻¹，而在灌溉定额为需水量50%的处理下，其水分利用效率为4.31 kg·ha⁻¹·mm⁻¹。