Amplified warming induced by large-scale application of water-saving techniques

Large-scale agricultural activities can exacerbate global climate change. In the past three decades, over 5 Mha of cultivated land have been equipped with Water-Saving Techniques (WST) in Northwest China to cope with water scarcity. However, the effect of WST on local climate and its mechanisms are not yet understood. Here we quantified the local climatic effect by comparing temperature and humidity at controlled and irrigated sites before and after the large-scale implementation of WST. Results show that the substantial reduction in irrigation water use has led to an average increase of 0.3°C in growing-season temperature and reduced relative humidity by 2%. Near-surface air temperature responds nonlinearly to percentage area of WST and a threshold value of 40% is found before any noticeable warming effect over the study area. Moreover, it is found that regions with relatively humid climates respond more significantly to WST. This study reveals the mechanism of WST on near-surface climate and highlights the importance of incorporating this feedback into sustainable water management and land-surface models for assessing the impact of irrigated agriculture on regional climate change.

Assessment of Non-Conventional Irrigation Water in Greenhouse Cucumber (Cucumis sativus) Production

Climate change, urbanization and subsequent environmental changes are depleting freshwater resources around the globe. The reuse of domestic, industrial and agricultural wastewater is an alternative approach to freshwater that can be used for irrigation purposes. However, these wastewaters may contain hazardous and toxic elements, such as heavy metals that are hazardous for human health and the environment. Therefore, an experiment was conducted to evaluate the concentration of macro, micro and heavy metals in cucumber irrigated with different resources (tap water, greywater, dairy water and wastewater). The results showed that the use of different irrigation resources has increased the level of macro (sodium (Na), potassium (K), calcium (Ca), magnesium (Mg)), microelements (zinc (Zn), iron (Fe), manganese (Mn)), and heavy metals (copper (Cu), barium (Ba), lead (Pb) and cadmium (Cd)) in cucumber leaves and fruits. However, their levels were in the range that is safe for human health and the environment was as recommended by FAO maximum values of trace elements (Zn, 2.0; Fe 1.0; Mn, 0.2; Cu, 0.2; Pb, 5.0, and Cd, 0.01 mgL−1). Based on observations, it was also revealed that among different irrigation resources, the use of dairy water in cucumber improved its agronomic attributes and maximum plant yield (1191.02 g), while the different irrigation resources showed a non-significant impact on fruit diameter. However, total soluble solid contents (TSS) were more significant in cucumber fruits treated with wastewater (2.26 °brix) followed by dairy water (2.06 °brix), while the least TSS contents (1.57 °brix) were observed in cucumber plants treated with tap water. The significance of non-conventional irrigation water use in agriculture, particularly greenhouse cucumber (Cucumis sativus) production, is discussed.

Efficacy of benzyladenine for compensating the reduction in soybean productivity under low water supply

Undoubtedly, drought is a negative consequence of climate change. Farmers have to deal with this issue and may be forced to irrigate their crops with less water than required, however reduction in productivity is anticipated. Thus, two–year field trials were conducted to assess the impact of irrigation regimes (60, 80 and 100% of crop evapotranspiration, denoted ET60, ET80, and ET100, respectively) and benzyladenine rates (0, 50, 100, 150 and 200 mg L−1, symbolized as BA0, BA50, BA100, BA150, BA200, respectively) on soybean. Findings clarified that the maximum increases in plant height and net assimilation rate were obtained with the interactions of ET100 or ET80 x BA200 or BA150 in both seasons. ET80 x BA200 (in both seasons) and ET100 x BA150 (in the first season) were as similar as ET100 x BA200 for enhancing pods number plant−1. Irrigation water use efficiency progressively increased with decreasing irrigation water amount and increasing benzyladenine rate. In conclusion, the reduction in seed yield due to lowering water supply up to 80% of crop evapotranspiration (with saving 20% of irrigation water) could be compensated using benzyladenine, 150 mg L−1, thus it should be involved in soybean irrigation programs.

Reduced Water Use in Barley and Maize Production Through Conservation Agriculture and Drip Irrigation

The Mexican Bajío region is the country's main barley (Hordeum vulgare) producing area. Barley is commonly produced during the dry autumn–winter season using furrow irrigation with ground water, following which rainfed maize (Zea mays) is grown in the spring–summer season using supplementary irrigation. Ground water levels in the region are steadily dropping, and the introduction of water-saving technologies in agriculture is urgently required. Drip irrigation can reduce water use but is costly. Conservation agriculture—the combination of minimal tillage, permanent soil cover and crop diversification—might reduce water use, but studies in irrigated systems are scarce. We compared water use and grain yield in tillage-based conventional agriculture and conservation agriculture, both with furrow irrigation and drip irrigation, in a 3-year (six growing seasons) barley-maize field experiment. Additionally, side-by-side demonstrations of conventional and conservation agriculture were installed simultaneously in farmers' fields and yields, water use and fuel use were recorded. In the field experiment, yields did not differ significantly between production systems, but irrigation water use was on average 17% lower in conservation agriculture than in conventional agriculture, ~36% lower with drip irrigation compared with furrow irrigation in conventional tillage, and 40% lower with drip irrigation and conservation agriculture combined compared with conventional agriculture with furrow irrigation. Water use reductions differed strongly between years, depending on weather. The water saving through conservation agriculture in farmers' fields was similar to the water saving in the controlled experiment with about 17%. Additionally, in farmer's fields conservation agriculture reduced greenhouse gas emissions by 192 kg CO2 ha−1 and improved soil health. The implementation of conservation agriculture would be a cost-effective method to reduce water use in the barley-maize production system in the Mexican Bajío, while simultaneously reducing greenhouse gas emissions.