In the dominant winter wheat （WW）-summer maize （SM） double cropping system in the low plain located in the North China, limited access to fresh water, especially during dry season, constitutes a major obstacle to ...In the dominant winter wheat （WW）-summer maize （SM） double cropping system in the low plain located in the North China, limited access to fresh water, especially during dry season, constitutes a major obstacle to realize high crop productivity. Using the vast water resources of the saline upper aquifer for irrigation during WW jointing stage, may help to bridge the peak of dry season and relieve the tight water situation in the region. A field experiment was conducted during 2009-2012 to investigate the effects of saline irrigation during WW jointing stage on soil salt accumulation and productivity of WW and SM. The experiment treatments comprised no irrigation （T1）, fresh water irrigation （T2）, slightly saline water irrigation （T3：2.8 dS m-l）, and strongly saline water irrigation （T4：8.2 dS m-1） at WW jointing stage. With regard to WW yields and aggregated annual WW-SM yields, clear benefits of saline water irrigation （T3 ＆ T4） compared to no irrigation （T1）, as well as insignificant yield losses compared to fresh water irrigation （T2） occurred in all three experiment years. However, the increased soil salinity in eady SM season in consequence of saline irrigation exerted a negative effect on SM photosynthesis and final yield in two of three experiment years. To avoid the negative aftereffects of saline irrigation, sufficient fresh water irrigation during SM sowing phase （i.e., increase from 60 to 90 mm） is recommended to guarantee good growth conditions during the sensitive early growing period of SM. The risk of long-term accumulation of salts as a result of saline irrigation during the peak of dry season is considered low, due to deep leaching of salts during regularly occurring wet years, as demonstrated in the 2012 experiment year. Thus, applying saline water irrigation at jointing stage of WW and fresh water at sowing of SM is most promising to realize high yield and fresh irrigation water saving.展开更多
Fruit yield, yield components, fruit mineral content, total phenolic content, antioxidant activity and irrigation water use efifciency （IWUE） of summer squash responses to different irrigation quantities were evalua...Fruit yield, yield components, fruit mineral content, total phenolic content, antioxidant activity and irrigation water use efifciency （IWUE） of summer squash responses to different irrigation quantities were evaluated with a ifeld study. Irrigations were done when the total evaporated water from a Class A pan was about 30 mm. Different irrigation quantities were adjusted using three different plant-pan coefifcients （Kcp, 100% （Kcp1）, 85% （Kcp2） and 70% （Kcp3））. Results indicated that lower irrigation quantities provided statistically lower yield and yield components. The highest seasonal fruit yield （80.0 t ha-1） was determined in the Kcp1 treatment, which applied the highest volume of irrigation water （452.9 mm）. The highest early fruit yield, average fruit weight and fruit diameter, length and number per plant were also determined in the Kcp1 treatment, with values of 7.25 t ha-1, 264.1 g, 5.49 cm, 19.95 cm and 10.92, respectively. Although the IWUE value was the highest in the Kcp1 treatment （176.6 kg ha-1 mm-1）, it was statistically similar to the value for Kcp3 treatment （157.1 kg ha-1 mm-1）. Total phenolic content and antioxidant activity of fruits was higher in the Kcp1 （44.27 μg gallic acid equivalents （GAE） mg-1 fresh sample） and in the Kcp2 （84.75%） treatments, respectively. Major （Na, N, P, K, Ca, Mg and S） and trace （Fe, Cu, Mn, Zn and B） mineral contents of squash fruits were the highest in the Kcp2 treatment, with the exception of P, Ca and Cu. Mineral contents and total phenolic content were signiifcantly affected by irrigation quantities, but antioxidant activity was not affected. It can be concluded that the Kcp1 treatment was the most suitable for achieving higher yield and IWUE. However, the Kcp2 treatment will be the most suitable due to the high fruit quality and relatively high yield in water shortage conditions.展开更多
Two independent SST atlases have confirmed that there is a double seasonal signal in the surface layer of the northwestern Indian Ocean. The area enclosed by the 80F isotherm increases from January to a maximum in May...Two independent SST atlases have confirmed that there is a double seasonal signal in the surface layer of the northwestern Indian Ocean. The area enclosed by the 80F isotherm increases from January to a maximum in May followed by a decrease, a cool-down, to August, which has been explained recently. Then there is a second maximum of warm surface area in October/November, called a “second summer” for convenience. A hypothesis is proposed to explain this unusual second summer feature by extrapolating from available data. During July, August and September, the sea level slopes downward from the equator to the north providing a horizontal force to drive the warm surface water accumulated in the equatorial region back into the NW Indian Ocean basin. New observations are needed to check up on the hypothesis.展开更多
In order to explore the appropriate irrigation schedule for summer maize,a field experiment was conducted in 2013 in Lubotan of Shaanxi Province.Soil water content,soil salinity,soil hydraulic parameters,crop growth p...In order to explore the appropriate irrigation schedule for summer maize,a field experiment was conducted in 2013 in Lubotan of Shaanxi Province.Soil water content,soil salinity,soil hydraulic parameters,crop growth parameters and summer maize yield were measured in the experiment.The SWAP model was calibrated based on field experiment observation data in 2013.The SWAP model was used to simulate and optimize irrigation schedule for summer maize after calibration.The results showed that model simulation results of soil water content,soil salinity and summer maize yield agreed well with the measured values.The Root Mean Square Error(RMSE)and Mean Relative Error(MRE)were within the allowable error ranges.The RMSE values were all lower than 0.05 cm3/cm3 and the MRE values were lower than 15%in soil water content calibration.The RMSE values were all lower than 0.1 mg/cm3 and the MRE values were lower than 20%in soil salinity calibration.The RMSE and MRE values were 1299.6 kg/hm2 and 15.26%in summer maize yield calibration.The model parameters suitable for the study area were obtained in calibration.The SWAP model could be used to simulate and optimize irrigation schedule for summer maize after calibration.The SWAP model was used to simulate soil water-salt balance,summer maize yield and water use efficiency under different irrigation schedules.The model simulation results for different irrigation schedules indicated that the optimal irrigation schedules of summer maize were three times each for jointing stage(July 5),heading stage(August 5)and grain filling stage(August 30)with irrigation amount of 128 mm,128 mm and 96 mm,respectively.The optimal irrigation quota was 352.0 mm for summer maize in the study area.展开更多
基金funded by the National Scientific and Technological Supporting Scheme,China (2013BAD05B02 )the Demonstration Plan of Modern Agriculture of Chinese Academy of Sciences (CXJQ120108-2)the support by the Sino-German Center for Research Promotion,Germany (GZ 1149)
文摘In the dominant winter wheat （WW）-summer maize （SM） double cropping system in the low plain located in the North China, limited access to fresh water, especially during dry season, constitutes a major obstacle to realize high crop productivity. Using the vast water resources of the saline upper aquifer for irrigation during WW jointing stage, may help to bridge the peak of dry season and relieve the tight water situation in the region. A field experiment was conducted during 2009-2012 to investigate the effects of saline irrigation during WW jointing stage on soil salt accumulation and productivity of WW and SM. The experiment treatments comprised no irrigation （T1）, fresh water irrigation （T2）, slightly saline water irrigation （T3：2.8 dS m-l）, and strongly saline water irrigation （T4：8.2 dS m-1） at WW jointing stage. With regard to WW yields and aggregated annual WW-SM yields, clear benefits of saline water irrigation （T3 ＆ T4） compared to no irrigation （T1）, as well as insignificant yield losses compared to fresh water irrigation （T2） occurred in all three experiment years. However, the increased soil salinity in eady SM season in consequence of saline irrigation exerted a negative effect on SM photosynthesis and final yield in two of three experiment years. To avoid the negative aftereffects of saline irrigation, sufficient fresh water irrigation during SM sowing phase （i.e., increase from 60 to 90 mm） is recommended to guarantee good growth conditions during the sensitive early growing period of SM. The risk of long-term accumulation of salts as a result of saline irrigation during the peak of dry season is considered low, due to deep leaching of salts during regularly occurring wet years, as demonstrated in the 2012 experiment year. Thus, applying saline water irrigation at jointing stage of WW and fresh water at sowing of SM is most promising to realize high yield and fresh irrigation water saving.
文摘Fruit yield, yield components, fruit mineral content, total phenolic content, antioxidant activity and irrigation water use efifciency （IWUE） of summer squash responses to different irrigation quantities were evaluated with a ifeld study. Irrigations were done when the total evaporated water from a Class A pan was about 30 mm. Different irrigation quantities were adjusted using three different plant-pan coefifcients （Kcp, 100% （Kcp1）, 85% （Kcp2） and 70% （Kcp3））. Results indicated that lower irrigation quantities provided statistically lower yield and yield components. The highest seasonal fruit yield （80.0 t ha-1） was determined in the Kcp1 treatment, which applied the highest volume of irrigation water （452.9 mm）. The highest early fruit yield, average fruit weight and fruit diameter, length and number per plant were also determined in the Kcp1 treatment, with values of 7.25 t ha-1, 264.1 g, 5.49 cm, 19.95 cm and 10.92, respectively. Although the IWUE value was the highest in the Kcp1 treatment （176.6 kg ha-1 mm-1）, it was statistically similar to the value for Kcp3 treatment （157.1 kg ha-1 mm-1）. Total phenolic content and antioxidant activity of fruits was higher in the Kcp1 （44.27 μg gallic acid equivalents （GAE） mg-1 fresh sample） and in the Kcp2 （84.75%） treatments, respectively. Major （Na, N, P, K, Ca, Mg and S） and trace （Fe, Cu, Mn, Zn and B） mineral contents of squash fruits were the highest in the Kcp2 treatment, with the exception of P, Ca and Cu. Mineral contents and total phenolic content were signiifcantly affected by irrigation quantities, but antioxidant activity was not affected. It can be concluded that the Kcp1 treatment was the most suitable for achieving higher yield and IWUE. However, the Kcp2 treatment will be the most suitable due to the high fruit quality and relatively high yield in water shortage conditions.
文摘Two independent SST atlases have confirmed that there is a double seasonal signal in the surface layer of the northwestern Indian Ocean. The area enclosed by the 80F isotherm increases from January to a maximum in May followed by a decrease, a cool-down, to August, which has been explained recently. Then there is a second maximum of warm surface area in October/November, called a “second summer” for convenience. A hypothesis is proposed to explain this unusual second summer feature by extrapolating from available data. During July, August and September, the sea level slopes downward from the equator to the north providing a horizontal force to drive the warm surface water accumulated in the equatorial region back into the NW Indian Ocean basin. New observations are needed to check up on the hypothesis.
基金This research was financially supported by Jiangxi Educational Bureau Science-Technology Research Program(GJJ170981)National Natural Science Foundation of China(51709144)and Farmland Irrigation Research Institute,Chinese Academy of Agricultural Sciences(FIRI2017-22-01).
文摘In order to explore the appropriate irrigation schedule for summer maize,a field experiment was conducted in 2013 in Lubotan of Shaanxi Province.Soil water content,soil salinity,soil hydraulic parameters,crop growth parameters and summer maize yield were measured in the experiment.The SWAP model was calibrated based on field experiment observation data in 2013.The SWAP model was used to simulate and optimize irrigation schedule for summer maize after calibration.The results showed that model simulation results of soil water content,soil salinity and summer maize yield agreed well with the measured values.The Root Mean Square Error(RMSE)and Mean Relative Error(MRE)were within the allowable error ranges.The RMSE values were all lower than 0.05 cm3/cm3 and the MRE values were lower than 15%in soil water content calibration.The RMSE values were all lower than 0.1 mg/cm3 and the MRE values were lower than 20%in soil salinity calibration.The RMSE and MRE values were 1299.6 kg/hm2 and 15.26%in summer maize yield calibration.The model parameters suitable for the study area were obtained in calibration.The SWAP model could be used to simulate and optimize irrigation schedule for summer maize after calibration.The SWAP model was used to simulate soil water-salt balance,summer maize yield and water use efficiency under different irrigation schedules.The model simulation results for different irrigation schedules indicated that the optimal irrigation schedules of summer maize were three times each for jointing stage(July 5),heading stage(August 5)and grain filling stage(August 30)with irrigation amount of 128 mm,128 mm and 96 mm,respectively.The optimal irrigation quota was 352.0 mm for summer maize in the study area.
