Advances in Research on the Approaches of Improving Water Utilization Efficiency in Rice

Water shortage is increasingly an important factor limiting the sustainable development of global economy, posing a hugethreat to social security and human existence. Water usage in agriculture accounts for about 70% of total water consumptionin the world, and rice cultivation is in turn the largest water user, which accounts for about 50% of total water usage inagriculture. Therefore, it is quite important to improve water utilization efficiency to reduce water consumption in rice.Water stress causes severe inhibition of plant growth and development as well as yield reduction, however the extent ofinhibition or reduction varies greatly with the growth stages, duration and severity of stress, and plant genotypes. In rice,drought resistance and water utilization efficiency might be improved by developing stress resistant cultivars and conductingproper agronomic practices. It is hence imperative to determine the suitable criteria in morphological and physiologicaltraits for drought resistance and water utilization efficiency in conventional breeding of rice. At present, leaf rolling, leafwater potential and carbon isotope discrimination are commonly used criteria for the evaluation and identification ofgermplasm with high drought resistance or water utilization efficiency. With rapid development of molecular biology,marker-assisted selection has been used in rice breeding against water stress. In this review, therefore, the agronomicaspect of water saving techniques such as selection of suitable rice cultivars, planting pattern, mulching, deficit irrigationand alternative drying and moist irrigation are discussed and effective approaches are also recommended.

Effects of Different Rainwater Diversion Patterns on Rainwater Collection Efficiency and Water Utilization Efficiency in Cornfield

Four rainwater diversion patterns including undisturbed soil ditch （T1）, slope compaction （T2）, asbestos sheet covering after compac- tion （T3） and plastic film covering after compaction （T4） were set in cornfield in arid areas of Yunnan Province, and effects of various patterns on rainwater collection efficiency, water utilization efficiency and corn yield were studied. The results shows that rainwater collection efficiency, water utilization efficiency and corn yield of the four diversion patterns presented the same trend, namely T4 〉T3 〉T2 〉T1. Overall, rainwater collection efficiencies of the four diversion patterns ranged from 41.7% to 58.7% ; compared with T1, water utilization efficiencies of T2 ,T3 and T4 increased by 34.9%, 53.5% and 92.5%, and maize yields of them improved by 1 767.0, 1 981.5 and 2 385.0 kg/hm2.

The Relationship between Water Resources Use Efficiency and Scientific and Technological Innovation Level: Case Study of Yangtze River Basin in China

The Yangtze River Basin’s water resource utilization efficiency(WUE)and scientific and technological innovation level(STI)are closely connected,and the comprehension of these relationships will help to improve WUE and promote local economic growth and conservation of water.This study uses 19 provinces and regions along the Yangtze River’s mainstream from 2009 to 2019 as its research objects and uses a Vector Auto Regression(VAR)model to quantitatively evaluate the spatiotemporal evolution of the coupling coordination degree(CCD)between the two subsystems of WUE and STI.The findings show that:(1)Both the WUE and STI in the Yangtze River Basin showed an upward trend during the study period,but the STI effectively lagged behind the WUE;(2)The CCD of the two subsystems generally showed an upward trend,and the CCD of each province was improved to varying degrees,but the majority of regions did not develop a high-quality coordination stage;(3)The CCD of the two systems displayed apparent positive spatial autocorrelation in the spatial correlation pattern,and there were only two types:high-high(H-H)urbanization areas and low-low(L-L)urbanization areas;(4)The STI showed no obvious response to the impact of the WUE,while the WUE responded greatly to the STI,and both of them were highly dependent on themselves.Optimizing their interaction mechanisms should be the primary focus of high-quality development in the basin of the Yangtze River in the future.These results give the government an empirical basis to enhance the WUE and promote regional sustainable development.

Experimental study on water-saving and emission-reduction effects of controlled drainage technology

Field experiments and laboratory analysis were carried out to determine the effects of controlled drainage（CTD） and conventional drainage（CVD） technologies on drainage volume, concentrations of NH4^＋ -N, NO3^-N, and total phosphorus（TP）, nitrogen and phosphorus losses, rice yield,and water utilization efficiency. Results show that CTD technology can effectively reduce drainage times and volume; NH4^＋ -N, NO3^-N, and TP concentrations, from the first to the fourth day after four rainstorms decreased by 28.7%e46.7%, 37.5%e47.5%, and 22.7e31.2%, respectively,with CTD. These are significantly higher rates of decrease than those observed with CVD. CTD can significantly reduce nitrogen and phosphorus losses in field drainage, compared with CVD; the reduction rates observed in this study were, respectively, 66.72%, 55.56%, and 42.81% for NH4^＋ -N, NO3^-N, and TP. Furthermore, in the CTD mode, the rice yield was cut slightly. In the CVD mode, the water production efficiencies in unit irrigation water quantity, unit field water consumption, and unit evapotranspiration were, respectively, 0.85, 0.48, and 1.22 kg/m^3, while in the CTD mode they were 2.91, 0.84, and 1.61 kg/m^3 din other words, 3.42, 1.75, and 1.32 times those of CVD. Furthermore, the results of analysis of variance（ANOVA） show that the indicators in both the CVD and CTD modes, including the concentrations of NH4^＋ -N, NO3^-N, and TP, the losses of NH4^＋ -N, NO3^-N, and TP, irrigation water quantity, and water consumption, showed extremely significant differences between the modes, but the rice yield showed no significant difference.

Water resource utilization efficiency and spatial spillover effects in China

Based on provincial panel data of water footprint and grey water footprint, and with the help of data envelopment analysis model considering and without considering the unde- sirable output, this paper estimates the water resources utilization efficiency in China from 1997 to 2011. The spatial weighting matrix based on economy-spatial distance function is established to discuss spatial autocorrelation of water resources utilization efficiency. With the help of absolute/3-convergence model, this paper concludes that there exists/%convergence in the water resources utilization efficiency. Under the conditions of considering and without considering the undesirable output, it takes about 52.6 and 5.6 years respectively to achieve the extent of half of convergence. By mean of the spatial Durbin econometric model, this paper studies spatial spillover effects of the provincial water resources utilization efficiency in China. The results are as follows. 1） With considering and without considering the undesir- able output, there is significant spatial correlation in provincial water resource efficiency in China. 2） Under the two cases, the spatial autoregressive coefficients （p） are 0.278 and 0.507 respectively, at 1% significance level. There exist the spatial spillover effects of provin- cial water resources utilization efficiency. 3） With considering the undesirable output, these factors of the education funds, the transportation infrastructure, and the industrial and agri- cultural water consumption proportion have positive impacts. These factors of foreign direct investment, the industry value-added water consumption per ten thousand yuan, per capita water consumption, and the total precipitation have negative impacts. 4） Without considering the undesirable output, the factor of GDP per laborer has a greater positive significant influ- ence on the water resources utilization efficiency. However the facts of industry value-added water consumption in ten thousand yuan and the transportation infrastructure have no sig- nificant influence. 5） Regardless of undesirable output of water resources utilization efficiency the assessment of the present real water resources utilization in China will be distorted and policy-making will be misled. The water efficiency measure considering environmental factors （such as gray water footprint） is more reasonable.