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Abstract:Global warming has resulted in increasingly frequent and severe drought and/or precipitation events. Severe drought limits crop water availability and impacts agricultural productivity and socioeconomic development. To quantify drought-induced yield loss during the main crop stages in Liaoning province, China, aspects of drought episodes (magnitude, duration, and frequency) were investigated during the period 1960-2015 using the Standardized Precipitation Index (SPI) and the Standardized Precipitation Evapotranspiration Index (SPEI), respectively. Then the relationship between the SPI/SPEI and the standardized yield residuals series (SYRS), and the drought-induced yield loss were analyzed for maize, rice, sorghum, soybean, and millet. Liaoning underwent a province-wide increase in temperature, reduced precipitation, and reduced reference crop evapotranspiration. As expected, Liaoning experienced province-wide meteorological drying trends during the main crop growth stages, while the drought frequency, duration, and magnitude were not as serious as revealed by using the SPI. As compared to the SPI, the SPEI considering potential evapotranspiration explained 39%-78% yield variability of SYRS and evaluated the drought-induced yield loss more accurately. The increased drought frequency mainly affected the rain-fed crops (maize, sorghum, soybean, and millet), while it did not reduce irrigated rice production. No major impact was exerted on the rain-fed crops caused by mild drought. However, severe drought (SPEI < −1.0) markedly reduced yield performance, in particular at the anthesis-silking stage for maize, the jointing-booting stage for sorghum, the flowering-podding stage for soybean, and the sowing-milking stage for millet. It is concluded that the SPEI is a more useful measure for the identification of drought episodes and the assessment of drought impact on agricultural production in Liaoning province.

Phosphorus (P) deficiency often occurs in paddy fields due to its high fixation, and low solubility and mobility in soils, especially under water stress. Available soil P and plant P uptake could be improved through the application of zeolite. However, little is known about the impact of zeolite on P uptake in rice under water stress. A two-year lysimetric experiment using a split-split plot design investigated the effects of zeolite (0 or 15 t ha−1) and P (0 or 60 kg ha−1) applications on water use, P uptake, and grain yield in rice under two irrigation management systems (continuous flooding irrigation (CF) and improved alternate wetting and drying irrigation (IAWD)). Both irrigation systems produced equivalent effective panicles and grain yield. Compared with CF, IAWD reduced water use and aboveground P uptake and improved water-use efficiency (WUE) in rice. The applications of zeolite or P alone increased grain yield, WUE, soil available P, and stem, leaf, and panicle P concentration, and aboveground P uptake, but had no significant effect on water use. The enhanced grain yield induced by zeolite was related to the increase in aboveground P uptake. The zeolite application enhanced NH4+–N retention in the topsoil and prevented NO3−–N from leaching into deeper soil layers. Moreover, Zeolite made lower rates of P fertilizer possible in paddy fields, with benefits for remaining P supplies and mitigating pollution due to excessive P. These results suggest that the combined application of zeolite and P under improved AWD regime reduced water use, improved P uptake and grain yield in rice, and alleviated environment risk.

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The effect of biochar application on photosynthetic traits and yield in peanut (Arachis hypogaea L.) is not well understood. A 2-year field experiment was conducted in Northwest Liaoning, China to evaluate the effect of biochar application [0, 10, 20, and 40 t ha−1 (B0, B10, B20, and B40)] on leaf gas exchange parameters, chlorophyll fluorescence parameters, and yield of peanut. B10 improved photochemical quenching at flowering and pod set and reduced non-photochemical quenching at pod set, relative to B0. B10 and B20 increased actual photochemical efficiency and decreased regulated energy dissipated at pod set, relative to B0. B10 significantly increased net photosynthetic rate, transpiration rate, stomatal conductance, and water use efficiency at flowering and pod set, relative to B0. Compared with B0, B10 significantly improved peanut yield (14.6 and 13.7%) and kernel yield (20.2 and 14.4%). Biochar application increased leaf nitrogen content. B10 and B20 significantly increased plant nitrogen accumulation, as compared to B0. The net photosynthetic rate of peanut leaves had a linear correlation with plant nitrogen accumulation and peanut yield. The application of 10 t ha−1 biochar produced the highest peanut yield by enhancing leaf photosynthetic capacity, and is thus a promising strategy for peanut production in Northwest Liaoning, China.

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