Mitigation fluctuations of inter-row water use efficiency of spring wheat via narrowing row space in enlarged lateral space drip irrigation systems

Abstract

Water use efficiency (WUE) is key indicator of balance between crop water demand and artificial water input in irrigation management. This makes specific importance of accurate evaluating largely diverse WUE of plants differently distant from the drip tube in the enlarged lateral space (ELS) drip irrigation wheat systems. To achieve this, we compared WUE calculated from differentiation of stable carbon isotopes (δ13C, WUE13 C), with those from grain yield (WUEYield) or dry matter accumulation (WUEDM) per evaportranspirated water in a two-year field trial with different ELS patterns in Xinjiang. Seven patterns were included, the normal ELS pattern by simply expanding drip tube to plant rows ratio from four (TR4, conventional pattern) to six (TR6) and eight (TR8) with row space (RS) of 15 cm; modified ELS by narrowing RS (NRS) to 10 cm to leave large inter-block space (IBS) of 35 cm and 45 cm for TR6L and TR8L, respectively; and Shortened IBS to 25 cm of TR6S and TR8S. Compared with TR4, ELS effectively improved all WUE parameters due to significant WUE increase in the outermost rows to drip tube, probably as a result of reduced received irrigation water (RIW). This led to large variations in WUE between rows, with inter-row coefficient of variation (C.V) of 6.2 %− 13.6 % for TR6 and TR8 (only 0.2 %− 2.3 % for TR4), respectively. The modified ELS patterns effectively reduced inter-row C.V to 2.9 %− 7.0 % for TR6L and TR8L, and 2.2 %− 5.7 % for TR6S and TR8S, respectively. NRS and SIBS effectively reduced the inter-row WUE heterogeneity, and facilitated overall yield and WUE. Considering satisfied WUE and high yield, TR6S was recommended the optimum ELS drip irrigation pattern. Moreover, WUE13 C was less fluctuant in response to reduced RIW as WUEDM and WUEYield, and was suggested proper indicator reflecting WUE of different rows in ELS patterns. The results should help guide better WUE evaluation under complex conditions and optimize more water-saving and productive drip irrigated wheat patterns.