Mulching Measures Improve Soil Moisture in Rain-Fed Jujube (Ziziphus jujuba Mill.) Orchards in the Loess Hilly Region of China

Water shortage is the main bottleneck restricting the sustainable development of rain-fed jujube (Ziziphus jujuba Mill.) orchards in the loess hilly region of China. Given the effect of mulching on soil moisture conservation, straw mulching (SM) and jujube branch mulching (BM) were applied to a rain-fed jujube orchard in this study. Soil moisture dynamics, soil water storage, water consumption, and soil moisture attenuation after typical rainfall under SM, BM, and clean tillage (CT) were studied. The results showed the following: (1) The 0–60 cm soil layer was the seasonal fluctuation layer of soil moisture under SM, BM, and CT in both the normal precipitation year and the dry year studied. The moisture contents of the 0–60, 60–160, and 160–280 cm soil layers under SM and BM were higher than that under CT in the three experimental years studied, and SM showed the most obvious effect of increasing soil moisture. (2) SM and BM showed a significant soil water storage effect in all of the jujube growth stages, and SM had a better water storage effect than BM. (3) SM reduced the amount of water consumption by 94.3, 60.8, and 121.3 mm compared to CT in the whole jujube growth period in 2014, 2015, and 2016, respectively. The amount of water consumption of BM decreased by 34.8 and 31.0 mm compared to that of CT in the whole growth period in 2014 and 2015, respectively. (4) CT had the maximum soil moisture loss rate under continuous drought after rainfall. The soil moisture loss rate of CT was above 37.3% on the eleventh day after typical rainfall in 2014, 2015, and 2016. With the extension of drought, the soil moisture loss rate under SM increased slowly. This study suggests that SM is the best mulching measure for rain-fed jujube orchards, and pruned jujube branches can also be used for in situ mulching to obtain a certain moisture conservation effect.