• Energy Research

To mitigate the climate change-induced water shortage and realize the sustainable development of agriculture, drip irrigation, a more efficient water-saving irrigation method, has been intensively implemented in most arid agricultural regions in the world. However, compared to traditional border irrigation, how drip irrigation affects the biophysical conditions in the cropland and how crops physiologically respond to changes in biophysical conditions in terms of water, heat and carbon exchange remain largely unknown. In view of the above situation, to reveal the mechanism of drip irrigation in improving spring wheat water productivity, paired field experiments based on drip irrigation and border irrigation were conducted to extensively monitor water and heat fluxes at a typical spring wheat field (Triticum aestivum L.) in Northwest China during 2017–2020. The results showed that drip irrigation improved yield by 10.3 % and crop water productivity (i.e., yield-to-evapotranspiration-ratio) by 15.6 %, but reduced LAI by 16.9 % in contrast with border irrigation. Under drip irrigation, the lateral development of spring wheat roots was promoted by higher soil temperature combined with frequent dry-wet alternation in the shallow soil layer (0–20 cm), which was the basis for efficient absorption of water and fertilizer, as well as efficient formation of photosynthate. Meanwhile, drip irrigation increased net radiation and decreased latent heat flux by inhibiting leaf growth, thereby increased sensible heat, causing a higher soil temperature (+1.10 ℃) and canopy temperature (+1.11 ℃). Further analysis proved that soil temperature was the key factor affecting yield formation. Based on the above conditions, the decrease in leaf distribution coefficient (−0.030) led to the decrease in evapotranspiration (−5.7 %) and the increase in ear distribution coefficient (+0.029). Therefore, drip irrigation emphasized the role of soil moisture in the soil-plant-atmosphere continuum, enhanced crop activity by increasing field temperature, especially soil temperature, and finally improved yield and water productivity via carbon reallocation. The study revealed the mechanism of drip irrigation for improving spring wheat yield, and would contribute to improving Earth system models in representing agricultural cropland ecosystems with drip irrigation and predicting the subsequent biophysical and biogeochemical feedbacks to climate change.

To mitigate the climate change-induced water shortage and realize the sustainable development of agriculture, drip irrigation, a more efficient water-saving irrigation method, has been intensively implemented in most arid agricultural regions in the world. However, compared to traditional border irrigation, how drip irrigation affects the biophysical conditions in the cropland and how crops physiologically respond to changes in biophysical conditions in terms of water, heat and carbon exchange remain largely unknown. In view of the above situation, to reveal the mechanism of drip irrigation in improving spring wheat water productivity, paired field experiments based on drip irrigation and border irrigation were conducted to extensively monitor water and heat fluxes at a typical spring wheat field (Triticum aestivum L.) in Northwest China during 2017–2020. The results showed that drip irrigation improved yield by 10.3 % and crop water productivity (i.e., yield-to-evapotranspiration-ratio) by 15.6 %, but reduced LAI by 16.9 % in contrast with border irrigation. Under drip irrigation, the lateral development of spring wheat roots was promoted by higher soil temperature combined with frequent dry-wet alternation in the shallow soil layer (0–20 cm), which was the basis for efficient absorption of water and fertilizer, as well as efficient formation of photosynthate. Meanwhile, drip irrigation increased net radiation and decreased latent heat flux by inhibiting leaf growth, thereby increased sensible heat, causing a higher soil temperature (+1.10 ℃) and canopy temperature (+1.11 ℃). Further analysis proved that soil temperature was the key factor affecting yield formation. Based on the above conditions, the decrease in leaf distribution coefficient (−0.030) led to the decrease in evapotranspiration (−5.7 %) and the increase in ear distribution coefficient (+0.029). Therefore, drip irrigation emphasized the role of soil moisture in the soil-plant-atmosphere continuum, enhanced crop activity by increasing field temperature, especially soil temperature, and finally improved yield and water productivity via carbon reallocation. The study revealed the mechanism of drip irrigation for improving spring wheat yield, and would contribute to improving Earth system models in representing agricultural cropland ecosystems with drip irrigation and predicting the subsequent biophysical and biogeochemical feedbacks to climate change.

AbstractBACKGROUNDIncreasing crop yield per unit area by increasing planting density is essential to ensure food security. However, the optimal combination of planting density and nitrogen (N) application for high‐yielding maize and its source–sink characteristics need to be more clearly understood.RESULTSA 2‐year field experiment was conducted combining three planting densities (D1: 70 000 plants ha−1; D2: 100 000 plants ha−1; D3: 130 000 plants ha−1) and three nitrogen rates (N1: 150 kg hm−2; N2: 350 kg hm−2; N3: 450 kg hm−2). The results showed that increasing planting density significantly increased leaf area index and grain yield but negatively affected ear traits. The Richards model was used to fit the dynamic changes of dry matter accumulation of maize under different treatments, and the fitting results were good. Increasing planting density increased population yield while limiting the development of individual plants, bringing the period of rapid dry matter accumulation to an early end and accelerating leaf senescence. An appropriate nitrogen rate could prolong the period of rapid accumulation of dry matter in maize, and increase the 100‐kernel weight. Increasing planting density enhanced post‐silking dry matter accumulation to a lesser extent, and the source–sink relationship of the maize population gradually developed from sink limitation to source limitation with increasing planting density.CONCLUSIONThe decrease in yield due to the insufficient source strength to meet the sink demand at too high densities was the reason that limited further improvement of the optimal planting density. An appropriate nitrogen rate facilitated the realization of yield potential at high density. © 2023 Society of Chemical Industry.

AbstractBACKGROUNDIncreasing crop yield per unit area by increasing planting density is essential to ensure food security. However, the optimal combination of planting density and nitrogen (N) application for high‐yielding maize and its source–sink characteristics need to be more clearly understood.RESULTSA 2‐year field experiment was conducted combining three planting densities (D1: 70 000 plants ha−1; D2: 100 000 plants ha−1; D3: 130 000 plants ha−1) and three nitrogen rates (N1: 150 kg hm−2; N2: 350 kg hm−2; N3: 450 kg hm−2). The results showed that increasing planting density significantly increased leaf area index and grain yield but negatively affected ear traits. The Richards model was used to fit the dynamic changes of dry matter accumulation of maize under different treatments, and the fitting results were good. Increasing planting density increased population yield while limiting the development of individual plants, bringing the period of rapid dry matter accumulation to an early end and accelerating leaf senescence. An appropriate nitrogen rate could prolong the period of rapid accumulation of dry matter in maize, and increase the 100‐kernel weight. Increasing planting density enhanced post‐silking dry matter accumulation to a lesser extent, and the source–sink relationship of the maize population gradually developed from sink limitation to source limitation with increasing planting density.CONCLUSIONThe decrease in yield due to the insufficient source strength to meet the sink demand at too high densities was the reason that limited further improvement of the optimal planting density. An appropriate nitrogen rate facilitated the realization of yield potential at high density. © 2023 Society of Chemical Industry.

Agricultural ecosystem water use efficiency (WUE) is an important indicator reflecting carbon-water coupling, but its control mechanisms in managed fields remain unclear. In order to reveal the influencing factors of WUE in the agricultural field under mulched drip irrigation (DM), we carried out the 8-year continuous observations in a maize field from Northwestern China. The structural equation model, relative importance analysis and principal component analysis were used to quantify the regulation effects of environmental and biological factors on WUE at different time scales, in different growth stages and under different hydrothermal conditions. The results showed that annual WUE varied between 2.18 g C Kg-1 H2O and 3.60 g C Kg-1 H2O, with a multi-year mean of 2.91 g C Kg-1 H2O. The total effects of air temperature on the daily WUE in the whole growth period, the vegetative growth stage, the warm and dry years, the cold and wet years, and the warm and wet years were the largest, with values of 0.61, 0.80, 0.70, 0.70 and 0.91 respectively. However, vapor pressure deficit and net radiation had the largest total effect in the cold and dry years (-0.63) and the reproductive growth stage (-0.49), respectively. Leaf biomass played a leading role in regulating the daily and interannual WUE, and the relative importance of leaf biomass to WUE in the vegetative growth stage was up to 75 %. In the warm and wet years, the relative importance of root biomass to WUE was 33 %, slightly higher than that of leaf biomass (31 %). At the same time, we found that Ta has the potential to increase WUE under future climate warming. Our results improve the understanding of carbon-water coupling mechanisms and provide important enlightenment on how crop ecosystems should adapt to future climate change.

Agricultural ecosystem water use efficiency (WUE) is an important indicator reflecting carbon-water coupling, but its control mechanisms in managed fields remain unclear. In order to reveal the influencing factors of WUE in the agricultural field under mulched drip irrigation (DM), we carried out the 8-year continuous observations in a maize field from Northwestern China. The structural equation model, relative importance analysis and principal component analysis were used to quantify the regulation effects of environmental and biological factors on WUE at different time scales, in different growth stages and under different hydrothermal conditions. The results showed that annual WUE varied between 2.18 g C Kg-1 H2O and 3.60 g C Kg-1 H2O, with a multi-year mean of 2.91 g C Kg-1 H2O. The total effects of air temperature on the daily WUE in the whole growth period, the vegetative growth stage, the warm and dry years, the cold and wet years, and the warm and wet years were the largest, with values of 0.61, 0.80, 0.70, 0.70 and 0.91 respectively. However, vapor pressure deficit and net radiation had the largest total effect in the cold and dry years (-0.63) and the reproductive growth stage (-0.49), respectively. Leaf biomass played a leading role in regulating the daily and interannual WUE, and the relative importance of leaf biomass to WUE in the vegetative growth stage was up to 75 %. In the warm and wet years, the relative importance of root biomass to WUE was 33 %, slightly higher than that of leaf biomass (31 %). At the same time, we found that Ta has the potential to increase WUE under future climate warming. Our results improve the understanding of carbon-water coupling mechanisms and provide important enlightenment on how crop ecosystems should adapt to future climate change.

Irrigation, as one of the most impactful human interventions in the terrestrial water cycle, has been arousing great attention due to research on the impacts of its interaction with climate. In this paper, we used a scientometric analysis method to explore the overall publication output of the climatic effects of irrigation (CEI) field from the Web of Science Core Collection (WSCC) database, covering the time period from 1993 to 2022. And, through a visual scientific citation analysis tool, CiteSpace, we studied the knowledge structure, disciplinary trajectory, frontier hotspots, and academic impacts in the field of CEI. Using topic screening, 2919 publications related to irrigation climate were searched. CEI research has gone through the knowledge germination stage (1993–2005), knowledge accretion stage (2006–2012), and the knowledge prosperity stage (2013–2022), respectively. Ecology, earth, and marine are the most influential disciplines of research in this field, and they are influenced by earth, geology, geophysics and plant, ecology, zoology. AWM and SOTTE are the most popular journals currently. The academic impacts of scientific stakeholders are uneven. European and American countries have profound influence in the research field. The keyword of “Climate change” is the turning point in the co-word analysis network, and research hotspots focus on “carbon dioxide”, “model”, “climate”, “growth”, “temperature”, “biomass”, “global warming”, “CO2”, “global change”, “dynamics”, “adjustments”, and “atmospheric CO2”. The knowledge base of the CEI field can be divided into 14 clusters, such as cotton production, semi-arid condition, and irrigation water supply, and these three clusters are the three largest among them. This paper offers a comprehensive scientometric review of CEI, and, to some degree, provides some reference for the relevant research on the climate effects of irrigation, which will be beneficial to understand the current research situation and development trend in this field, as well as provide state-of-the-art and future perspectives.

Irrigation, as one of the most impactful human interventions in the terrestrial water cycle, has been arousing great attention due to research on the impacts of its interaction with climate. In this paper, we used a scientometric analysis method to explore the overall publication output of the climatic effects of irrigation (CEI) field from the Web of Science Core Collection (WSCC) database, covering the time period from 1993 to 2022. And, through a visual scientific citation analysis tool, CiteSpace, we studied the knowledge structure, disciplinary trajectory, frontier hotspots, and academic impacts in the field of CEI. Using topic screening, 2919 publications related to irrigation climate were searched. CEI research has gone through the knowledge germination stage (1993–2005), knowledge accretion stage (2006–2012), and the knowledge prosperity stage (2013–2022), respectively. Ecology, earth, and marine are the most influential disciplines of research in this field, and they are influenced by earth, geology, geophysics and plant, ecology, zoology. AWM and SOTTE are the most popular journals currently. The academic impacts of scientific stakeholders are uneven. European and American countries have profound influence in the research field. The keyword of “Climate change” is the turning point in the co-word analysis network, and research hotspots focus on “carbon dioxide”, “model”, “climate”, “growth”, “temperature”, “biomass”, “global warming”, “CO2”, “global change”, “dynamics”, “adjustments”, and “atmospheric CO2”. The knowledge base of the CEI field can be divided into 14 clusters, such as cotton production, semi-arid condition, and irrigation water supply, and these three clusters are the three largest among them. This paper offers a comprehensive scientometric review of CEI, and, to some degree, provides some reference for the relevant research on the climate effects of irrigation, which will be beneficial to understand the current research situation and development trend in this field, as well as provide state-of-the-art and future perspectives.

The Soil–Water–Atmosphere–Plant (SWAP) model does not have a mulching module to simulate the effect of film mulching on soil water, heat dynamics and crop growth. In this study, SWAP model parameters were selected to simulate the soil water–heat process and crop growth, taking into account the effect of film mulching on soil evaporation, temperature, and crop growth, in order to predict the influence of future climate change on crop growth and evapotranspiration (ET). A most suitable scheme for high yield and water use efficiency (WUE) was studied by an experiment conducted in the Shiyang River Basin of Northwest China during 2017 and 2018. The experiment included mulching (M1) and non-mulching (M0) under three drip irrigation treatments, including full (WF), medium (WM), low (WL) water irrigation. Results demonstrated that SWAP simulated soil water storage (SWS) well, soil temperature at various depths, leaf area index (LAI) and aboveground dry biomass (ADB) with the normalized root mean square error (NRMSE) of 16.2%, 7.5%, 16.1% and 16.4%, respectively; and yield, ET, and WUE with the mean relative error (MRE) of 10.5%, 12.4% and 14.8%, respectively, under different treatments on average. The measured and simulated results showed film mulching could increase soil temperature, promote LAI during the early growth period, and ultimately improve ADB, yield and WUE. Among the treatments, M1WM treatment with moderate water deficit and film mulching could achieve the target of more WUE, higher yield, less irrigation water. Changes in atmospheric temperature, precipitation, and CO2 concentration are of worldwide concern. Three Representative Concentration Pathway (RCP) scenarios (RCP2.6, RCP4.5, RCP8.5) showed a negative effect on LAI, ADB and yield of seed-maize. The yield of seed-maize on an average decreased by 33.2%, 13.9% under the three RCPs scenarios for film mulching and non-mulching, respectively. Predicted yields under film mulching were lower than that under non-mulching for the next 30 years demonstrating that current film mulching management might not be suitable for this area to improve crop production under the future climate scenarios.