Understanding the effects of irrigation regime and soil texture on potassium-use efficiency (KUE) of rice (Oryza sativa. L) is essential for improving rice productivity. In this regard, experiments were conducted from July to October in 2016 and 2017 by using a randomized complete block design in a factorial arrangement with four replications. The rice plants were grown in three soils, with clay contents of 40%, 50%, and 60%, which were marked as S _(40%), S _(50%), and S _(60%), respectively. For each soil type, irrigation regimes, namely, R _{(F, S100%)}, R _{(F, S90%)}, and R _{(F, S70%)}, were established by setting the lower limit of irrigation to 100%, 90%, and 70% of saturated soil water content, respectively, and the upper limit of irrigation with 30 mm of flooding water above the soil surface for all irrigation regimes. Results showed that the responses of the roots and shoots and the potassium accumulation (KA) and KUE of rice were significantly affected by the water regime and soil texture. In the same irrigation regime, increasing the soil clay content improved the K utilization of rice. Under the same soil type, R _{(F, S100%)} was the optimal water management practice for growing rice. The R _{(F, S100%)} S _(60%) treatment presented the highest KUE, which was 56.4% in 2016 and 68.1% in 2017. The R _{(F, S70%)} S _(40%) treatment showed the lowest KUE, which was 13.8% in 2016 and 14.9% in 2017. These results enrich knowledge regarding the relationship among soil, water, and rice, and provide valuable insights on the effect of irrigation regime and soil texture on the KA and KUE of rice.

A two-year field experiment was executed to investigate the impact of different controlled irrigation and drainage regimes on the morphological and mechanical traits related to the lodging resistance of rice in Jiangsu province, China. Three irrigation regimes were comprised of conventional flooding practices (CK), controlled irrigation and drainage mode I (CID-1), and controlled irrigation and drainage mode II (CID-2). Results indicated that there was no significant difference in the heights of rice plants under the three irrigation regimes, but the average diameter of CK treatment was 21% higher than that of CID-2 in the 2013 season. Similarly, the value of the section modulus of CK was significantly higher than that of CID-2 (p < 0.05). On the contrary, the length of basal internodes of CK and CID-1 was significantly lower than that of CID-2 in 2013 (p < 0.05). For both seasons, the safety factor against stem breakage (SFs) of CID-2 always had the lowest value under different irrigation regimes, which might be related to the significantly lower values of bending strength of culm at breaking (S) and the bending stress (BS) as well as lower ash content and cellulose content in CID-2 compared with CK and CID-1. Collectively, properly increasing the depth of water levels after heavy rain under the current water-saving mode (CID-1) would not increase the risk of lodging for rice plants, whereas if the water depth after heavy rain was kept higher than 20 cm (CID-2), the SFs would be significantly lower than that of CK, and the rice plants would be much more likely to undergo lodging.

Aquaculture wastewater contains considerable quantities of organic matter, nitrogen, and phosphorus. Irrigation of paddy rice with aquaculture wastewater can make full use of water and fertilizer, which has practical significance for alleviating water-use conflicts in the coastal areas of Jiangsu Province and promoting soil desalinization. Our objective in this study was to evaluate the effects of water quality indexes of surface discharge in paddy fields, total nitrogen (TN) and total phosphorus (TP) losses of discharge in paddy fields, growing indexes of plants, grain yield, as well as soil salinity affected by the different irrigation treatments. To achieve this objective, experiments were conducted from May to October in 2017. There were four treatment combinations: I1W1 (shallow–frequent irrigation and aquaculture wastewater), I2W1 (shallow–wet irrigation and aquaculture wastewater), I3W1 (flooding irrigation and aquaculture wastewater), and I1W2 (shallow–frequent irrigation and fresh water). The results revealed that there was no significant difference in grain yield among the three wastewater irrigation treatments. Meanwhile, the values of water quality indexes were optimal in I3W1; the total losses of TN and TP of the I3W1 treatment were the lowest over the three important growth stages; the desalinization rate of I3W1 was the largest due to its long hydraulic retention time and large irrigation depth. The overall results suggested that the I3W1 treatment was the optimal treatment.