Growth Period Of Winter Wheat Research Articles

Meteorological disaster disturbances on the main crops in the north‒south transitional zone of China

Global climate change, with warming as its main feature, has altered the spatial-temporal evolution of factors such as precipitation and temperature that can cause meteorological disasters. The complex and changeable climate has led to frequent natural disasters, while the frequency and intensity of extreme climate events have also significantly increased, posing an enormous threat to societal production and human life. As the most important geoecological transitional zone of mainland China, the stability of agricultural production in China’s north–south transitional zone is crucial for ensuring food security under climate change. With the use of daily precipitation and potential evapotranspiration data from 1961 to 2018, this study focused on analysing disturbances such as extreme precipitation and drought disasters at different time scales during the winter wheat and summer maize growing seasons in the north–south transitional zone of China from an agricultural production perspective and attempted to answer the following questions: first, from an agricultural production perspective, what are the temporal and spatial distribution patterns of extreme precipitation and arid climate events in the north–south transitional zone? Second, which areas are at high risk of being disturbed by different types of meteorological disasters and require increased attention? The results indicated that (1) in terms of the overall temporal variation, the degree of extreme precipitation and drought stress faced by agricultural production in the region is decreasing. However, the temporal variation at each station in the north–south transitional zone was not completely consistent with the overall trend, and both increasing and decreasing trends were observed. The sites exhibiting an increase overlapped with typical regions of the north–south transitional zone to varying degrees, indicating that the typical regions represented not only theoretical potential risk areas under climate change but also suffered from meteorological disaster disturbances. (2) The precipitation distribution during the winter wheat growth period in the south–north transitional zone was uneven and varied significantly. High values of extreme precipitation indices during the winter wheat growth period were mainly concentrated in the southern part of the eastern section of the north‒south transitional zone. The precipitation distribution during the summer maize growth period significantly differed, with the highest amount of heavy rain and largest number of rainstorm days concentrated in the southeastern part of the north‒south transitional zone. The spatial distribution of the drought frequency in the north–south transitional zone, as indicated by the monthly standardized precipitation evapotranspiration index (SPEI1), showed that the areas with high total drought frequencies were mainly concentrated in northeast Jiangsu, southeast Henan, and north Anhui, which primarily experienced light drought. The central part of Jiangsu Province exhibited a high frequency of moderate drought, while southern Jiangsu Province and southwestern Shaanxi Province were prone to severe drought. Additionally, southeastern Hebei and eastern Henan were identified as areas with a high frequency of extreme drought. Finally, the central region of Sichuan Province was characterized by both severe and extreme drought conditions. Based on the SPEI12-derived spatial distribution of the drought frequency in the north–south transitional zone, the areas with a high total drought frequency were mainly concentrated in central and eastern Henan, southeast Shaanxi, southeast Shandong, and central Sichuan, which primarily experienced light to moderate drought. The northwestern part of Jiangsu, the southern part of Hebei, and the western part of Shandong are regions with a high frequency of severe drought, while the eastern part of Henan is an area with high frequencies of both severe and extreme drought. (3) High-value areas of extreme precipitation and drought disturbance in the north–south transitional zone overlapped with the edge of the transitional zone to varying degrees. Approximately 63.58% of the north‒south transitional zone of China was characterized by moderate or high stress levels, primarily concentrated along the southern boundary and central core area, and nearly 39.5% of all counties experienced two or more types of disaster stresses.

Analysis of the Spatial-Temporal Distribution Characteristics of Climate and Its Impact on Winter Wheat Production in Shanxi Province, China, 1964-2018.

The possible influence of global climate changes on agricultural production is becoming increasingly significant, necessitating greater attention to improving agricultural production in response to temperature rises and precipitation variability. As one of the main winter wheat-producing areas in China, the temporal and spatial distribution characteristics of precipitation, accumulated temperature, and actual yield and climatic yield of winter wheat during the growing period in Shanxi Province were analysed in detail. With the utilisation of daily meteorological data collected from 12 meteorological stations in Shanxi Province in 1964-2018, our study analysed the change in winter wheat yield with climate change using GIS combined with wavelet analysis. The results show the following: (1) Accumulated temperature and precipitation are the two most important limiting factors among the main physical factors that impact yield. Based on the analysis of the ArcGIS geographical detector, the correlation between the actual yield of winter wheat and the precipitation during the growth period was the highest, reaching 0.469, and the meteorological yield and accumulated temperature during this period also reached its peak value of 0.376. (2) The regions with more suitable precipitation and accumulated temperature during the growth period of winter wheat in the study area had relatively high actual winter wheat yields. Overall, the average actual yield of the entire region showed a significant increasing trend over time, with an upward trend of 47.827 kg ha-1 yr-1. (3) The variation coefficient of winter wheat climatic yield was relatively stable in 2008-2018. In particular, there were many years of continuous reduction in winter wheat yields prior to 2006. Thereafter, the impact of climate change on winter wheat yields became smaller. This study expands our understanding of the complex interactions between climate variables and crop yield but also provides practical recommendations for enhancing agricultural practices in this region.

A novel habitat adaptability evaluation indicator (HAEI) for predicting yield of county-level winter wheat in China base on multisource climate data from 2001 to 2020

The effective collaboration between crop habitat adaptability evaluation and yield prediction is of great significance. Climate factors occupy an indispensable role, but the contributions of different climate factors to crop growth present spatiotemporal heterogeneity and confusion, amplifying the challenges associated with large-scale dynamic evaluations. Additionally, the mounting input parameters in yield prediction compound the uncertainty and intricacy of modeling. To address these challenges, a climate-driven dynamic habitat adaptability evaluation indicator (HAEI) was developed, capable of forecasting county-level winter wheat yields in China. First, the distribution characteristics and matching relationship between climate and yield variability were explored from multi-source data in the long time series, and a novel method of multiple-factor adaptive matching habitat membership degree was proposed. Second, considering the interaction and contribution differences between multiple-factor at different phenological periods, a comprehensive HAEI suitable for the entire growth period of winter wheat is constructed. The results showed that HAEI can integrate climate information that has a greater impact on yield variability and has a significant correlation with yield in various regions and periods, with an average correlation of 0.70. Remarkably, the predictive models incorporating HAEI consistently outperformed other yield prediction algorithms, demonstrating superior accuracy (R2 = 0.62–0.76, nRMSE = 0.1517–0.2031). Even in the least favorable scenario, involving a linear model with HAEI input, satisfactory results were achieved. This comprehensive framework effectively mitigates the adverse consequences of widespread agricultural climate heterogeneity and evaluates the habitat adaptability and yield status of wheat at the county level in China.

Loss of Net primary production of seasonal winter wheat due to multiple drought types in the main Grain-Producing area of China

Droughts have a severe impact on ecosystems and food security. Net primary production (NPP), a critical component of the carbon cycle of an ecosystem, is strongly associated with crop yield and serves as an indicator of drought impact. In the present study, the loss of NPP in seasonal winter wheat was evaluated through an analysis of the changes in frequency and probability of exceeding NPP loss. This study also analyzed the drought thresholds for various types of drought, namely meteorological drought (MD), natural agricultural drought (NAD), and actual agricultural drought (AAD), in the North China Plain (NCP). The standardized precipitation evapotranspiration index, Palmer Drought Severity Index, and Vegetation Health Index were used to define these drought categories. The study findings reveal that although the NCP has experienced increased dryness, the severity of AAD has decreased. Within the study period, the frequency of winter wheat NPP loss due to drought in the area was within the range of 30% to 40%, with higher sensitivity to drought occurring during the middle growth period of winter wheat and in the NCP’s dry subhumid region. The highest probability of NPP loss was observed in March in the humid and dry subhumid regions of the NCP and in April in the semiarid region. Farmers in the NCP can effectively cope with extreme loss caused by drought. However, they have less experience with handling mild and moderate losses, which were the primary forms of NPP loss during the study period, particularly in the semiarid region. To ensure NPP can be sustained at a normal level or increased, MD and AAD must be prevented during the growing period of winter wheat, and NAD in the semiarid region must be managed to ensure its effects remain mild. Furthermore, farmers’ management of AAD may lead winter wheat to have a higher tolerance to MD and NAD. Our results deepen the understanding of seasonal NPP loss in winter wheat due to different types of drought, providing practical assistance to farmers in the region.

Sustainable nitrogen placement depth under different rainfall levels can enhance crop productivity and maintain the nitrogen balance in winter wheat fields

The deep placement of nitrogen (N) fertilizer is considered as an effective strategy for crop growth and yield formation. However, it is unclear how deep N fertilizer placement under different rainfall levels might affect the nitrogen balance of winter wheat fields. Thus, we conducted a two-year field experiment in a semi-humid region to assess the effects of different N fertilizer placement depths of 5 cm (D5), 15 cm (D15), 25 cm (D25), and 35 cm (D35) under three rainfall levels during winter wheat growth period (dry year = 125 mm, T1; normal year = 200 mm, T2; wet year = 275 mm, T3) on the N balance and crop productivity in winter wheat fields. Our results indicated that compared to D5, deeper N placement treatments increased the crop yield by 0.1–1.1 t ha–1 and N uptake by 3.0–18.0%, and reduced gaseous N losses by 0.2–1.1 kg N ha–1 under T1 and T2 (p < 0.05). T3D15 decreased the gaseous N losses by 1.2 kg N ha–1 compared with T3D5, and increased the yield and crop N uptake by 0.7–0.9 t ha–1 and 10.0–20.1 kg N ha–1 compared with T3D25 and T3D35, respectively (p < 0.05). T1 and T2 helped to maintain the N balance under deeper N placement (p < 0.05). Although T3 significantly increased NO3–-N concentration in the 60–100 cm soil layer and decreased the crop N uptake under D25 and D35, which was not conducive to maintaining the N balance, while D15 was beneficial in maintaining N balance (p < 0.05). Placement of N fertilizer at depths of 13.5 cm, 17.5 cm, and 21.6 cm in the wet year (T3), normal year (T2), and dry year (T1), respectively, could maintain the N balance in winter wheat fields through increasing crop N uptake, reducing gaseous N losses, and preserving the soil N pool.

Combining conservation tillage with nitrogen fertilizer measures promotes maize straw decomposition by regulating microbial community and enzyme activities

Straw return can effectively improve the farmland soil microenvironment and soil fertility. However, excessive straw in the topsoil adversely affects seed germination and crop growth. At present, the characteristics and key driving factors of straw decomposition in dry farmlands are unclear. Based on the interaction between three tillage practices (i.e., zero-till (ZT) and chisel-till (CPT) vs. conventional plow-till (PT)) and three nitrogen fertilizer rates (i.e., low nitrogen (N1: 180 kg N ha-1) and high nitrogen (N3: 300 kg N ha-1) vs. normal nitrogen (N2: 240 kg N ha-1)), quantitative polymerase chain reaction (qPCR) technology and an enzymatic detection kit were used to investigate the effects of key straw-decomposition enzyme activities and microbial abundance on straw decomposition during the growth period of winter wheat. Between 2018 and 2020, repeated in situ measurements of straw decomposition indicated that zero-till and chisel-till significantly increased winter wheat yield (ZT: 10.94%; CPT: 12.79%) and straw decomposition velocity (ZT: 20%; CPT: 26.67%), compared with plow-till. N2 (240 kg N ha-1) significantly increased wheat yield (N1: 4.65%; N3: 5.31%) and straw decomposition velocity (N1: 26.33%; N3: 13.21%), compared to N1 (180 kg N ha-1) and N3 (300 kg N ha-1), respectively. The partial least squares pathway model showed significant positive direct effects of soil moisture, NO3-, NH4+, total nitrogen, bacteria, cellulase, laccase and xylanase activities on straw decomposition, while pH, fungi and Actinomycetes had significant negative direct effects on straw decomposition. Overall, conservation tillage (zero-till and chisel-till) combined with N2 (240 kg N ha-1) is beneficial for straw decomposition in the drylands of the Loess Plateau and improve straw resource utilization and basic soil fertility. The results of the study clarify the key drivers of straw decomposition in dryland farmlands, and provide new ideas for developing updated soil management practices and adaptive nitrogen application strategies to promote the resource utilization of straw and achieve the goals of carbon peaking and carbon neutrality.

Climate warming extends the effective growth period of winter wheat and increases grain protein content

Climate warming causes an impact on the protein supplied to grains by affecting the winter wheat growth period and yield formation; however, research on the effects of warming on protein formation of winter wheat grains is limited. We investigated this phenomenon by conducting no-tillage (NT) and conventional tillage (CT) field warming trials in the North China Plain for four consecutive years (2017–2020). The results showed that warming significantly advanced the re-greening period and extended the effective growth period of winter wheat. Warming also improved the physiological characteristics of winter wheat as well as N accumulation in the stems and leaves during anthesis, facilitating the transport of N to the grains. Moreover, warming reduced the number of fertile spikelets in winter wheat and diverted N that would otherwise be supplied to produce more grains to the final effective grains, resulting in a significant increase in grain protein content (15.75% in CT, 19.11% in NT; p < 0.05). Our findings suggest that winter wheat can partially counteract the adverse effects of climate warming on its grain protein content. This study further elucidates the effect of climate warming on the protein content of winter wheat grains.

Evapotranspiration of Winter Wheat in the Semi-Arid Southeastern Loess Plateau Based on Multi-Source Satellite Data

Continuous monitoring of evapotranspiration (ET) at high spatio-temporal resolutions is vital for managing agricultural water resources in arid and semi-arid regions. This study used the enhanced spatial and temporal adaptive reflectance fusion model (ESTARFM) to calculate the ET of winter wheat between the green-up and milk stages in Linfen Basin, a typical, semi-arid area of the Loess Plateau, at temporal and spatial resolutions of 30 m and 8 d, respectively. We then analyzed the impact of meteorological factors on ET and its variation during the main growth period of winter wheat. The fused ET data displayed the spatial details of the OLI ET data better and could accurately reflect ET variation and local sudden variations during the main growth period of winter wheat. Moreover, winter wheat ET in rain-fed areas is more heavily influenced by meteorological factors, and the effect is more direct. Affected by the synergistic effect of wind velocity, precipitation, and temperature, the ET of winter wheat in rain-fed area was lower in the green-up stage. Then, ET gradually increased, reaching its maximum in the heading–grain filling stage. At the jointing stage, temperature had a significant effect on ET. A combination of precipitation and temperature had the greatest impact on the ET of winter wheat in the heading–filling stage. In the milk stage, meteorological factors had a minor impact on ET. This study serves as a reference for ET in winter wheat in semi-arid areas and its influencing meteorological factors, which can assist in drought mitigation and regional food security strategies.

Correlation of climate change and human activities with agricultural drought and its impact on the net primary production of winter wheat

Drought is a major natural disaster worldwide. Understanding the correlation between meteorological drought (MD) and agricultural drought (AD) is essential for relevant policymaking. In this paper, standardized precipitation evapotranspiration index and standardized soil moisture index were used to estimate the MD and AD in the North China Plain (NCP) to identify the correlation between MD and AD during the growth period of winter wheat. In addition, we investigated the contributions of climate change (CC) and human activity (HA) to AD and the factors influencing the loss of winter wheat net primary production (NPP). Drought propagation time (PT) increased spatially from the southern to northern NCP (from 3 to 11 months). PT first increased and then decreased during the phenological period of winter wheat, and the decreasing trend was delayed with an increasing latitude. In general, the relative contribution of CC to AD was higher than that of HA; the correlation between MD and AD exhibited a weakening trend, particularly during the middle and late phenological stages of winter wheat. Precipitation was the main driver of the effects of HA on AD; the effects were stronger in areas with less precipitation. However, because of the improved irrigation conditions and scarce rainfall during the growth period of winter wheat in the study area, the effects of precipitation on AD were nonsignificant. Instead, temperature, wind, and total solar radiation, which are highly correlated with evapotranspiration, were identified as the primary drivers of AD; spatiotemporal variations were noted in these correlations. Prolonged drought PT reduced NPP; the sensitivity of winter wheat NPP to AD was higher in humid areas than in semiarid or semihumid areas. NPP loss occurred primarily due to HA. Our findings revealed a correlation between MD and AD in agroecosystems and may facilitate policymaking related to drought mitigation and food security.

In-season assessment of agronomic nitrogen use efficiency and its components in winter wheat using critical nitrogen dilution curve.

Accurate and timely nitrogen (N) scheduling requires knowledge of in-season crop N deficit. Therefore, understanding the association between crop growth and crop N demand during its growth period is imperative for fine-tuning N scheduling decisions to actual crop N demand and to enhance N use efficiency. The concept of the critical N dilution curve has been employed to assess and quantify the intensity and time of crop N deficit. However, research regarding the association between crop N deficit and N use efficiency in wheat is limited. The present study was carried out to determine whether there are relationships between the accumulated nitrogen deficit (Nand) and agronomic N use efficiency (AEN) as well as with its components (N fertilizer recovery efficiency (REN) and N fertilizer physiological efficiency (PEN)) of winter wheat and to explore the potential capacity of Nand for predicting AEN and its components. Data acquired from five variable N rates (0, 75, 150, 225, and 300kg ha-1) field experiments using six winter wheat cultivars were used to establish and validate the relationships between Nand and AEN, REN, and PEN. The results indicated that plant N concentration in winter wheat was significantly affected by N application rates. Nand varied from -65.73 to 104.37kg ha-1 after Feekes stage 6 under different N application rates. The AEN and its components were also affected by cultivars, N levels, seasons, and growth stages. A positive correlation was observed between Nand, AEN, and its components. Validation using an independent data set showed the robustness of the newly developed empirical models to accurately predict AEN, REN, and PEN with an RMSE of 3.43kg kg-1, 4.22%, and 3.67kg kg-1 and RRMSE of 17.53%, 12.46%, and 13.17%, respectively. This indicates that Nand has the potential to predict AEN and its components during the growth period of winter wheat. The findings will assist in improving in-season N use efficiency by fine-tuning N scheduling decisions in winter wheat cultivation.

Linear dependency of winter wheat yield and nitrogen use efficiency on the pre-anthesis temperature in the lower reach of the Yangtze River

Global warming is expected to enhance the nitrogen (N) absorption capability of crops, which causes a change in nitrogen fertilizer input. However, the impacts of warming and nitrogen application on crop growth, yield and nitrogen use efficiency (NUE) are still unclear. Here, we conducted a 4-year field experiment of nighttime warming before winter wheat anthesis to explore the response of winter wheat yield to warming and the variation in nitrogen use efficiency under different nitrogen application levels (N150: 150 kg·ha−1, N225: 225 kg·ha−1, and N375: 375 kg·ha−1). The results showed that warming shortened the winter wheat vegetative growth period (VGP) by 8.3 days, while it prolonged the reproductive growth period (RGP) by 6.7 days. However, there was no significant difference in the growth period of winter wheat between nitrogen treatments. Meanwhile, warming increased winter wheat yield by increasing the number of effective spikes and grains per spike. Every 1 °C increase in pre-anthesis temperature increased winter wheat yield by 45.48, 55.78 and 60.88 g·m−2 for the N150, N225 and N375 treatments, respectively. There was no significant difference in yield between the N225 and N375 treatments, but the nitrogen partial factor productivity (PFPN) and the nitrogen utilization efficiency (NUtE) of N225 were significantly higher than those of N375. PFPN and NUtE were positively correlated with pre-anthesis air temperature under different nitrogen treatments. Multiple linear regression showed that a 1.0 °C increase enhanced NUtE by 11.62%, 9.75% and 7.85% for the N150, N225 and N375 treatments, respectively, and enhanced the PFPN by 7.77%, 8.94% and 9.81% respectively. Therefore, we suggest that 225 kg·ha−1 is an appropriate amount of nitrogen application in the lower reach of the Yangtze River under future climate warming.

Biochar reduces uptake and accumulation of polycyclic aromatic hydrocarbons (PAHs) in winter wheat on a PAH-contaminated soil

Biochar has been used previously for remediation of polycyclic aromatic hydrocarbons (PAHs) in contaminated soils for years, which has achieved remarkable results in improving removal of soil PAHs and reducing PAHs uptake in crops. However, the underlying mechanism of biochar application in reducing the uptake and accumulation of PAHs in winter wheat remains unclear. Pot trials using PAHs-contaminated soils were conducted for whole plant growth period of winter wheat, which were amended with 2% (w/w) bamboo biochar (BB), coconut shell biochar (CB) and maize straw biochar (MSB) or not (CK). Compared with CK, application of the three types of biochar significantly (p < 0.01) reduced grain PAHs concentration, the total equivalent concentration (TEC) values and the incremental lifetime cancer risk (ILCR) of grain PAHs, indicating that application of biochar reduced the exposure risk of PAHs in wheat grain, especially for MSB. Consistently, application of the three types of biochar significantly (p < 0.05) reduced uptake and accumulation of PAHs in root and stem of wheat, which may be due to that application of biochar enhanced the degradation of PAHs in the rhizosphere soil. Compared with CK, application of the three types of biochar significantly (p < 0.05) reduced the concentration of PAHs in the rhizosphere soil by 15.9%, 26.1% and 33.7%, respectively. It was found that the degradation rate of HMW PAHs (high molecular weight PAHs, 5-6 ring PAHs) was significantly (p < 0.05) higher than that of LMW PAHs (low molecular weight PAHs, 2-4 ring PAHs) regardless of types of biochar used. Additionally, application of the three types of biochar significantly increased the relative abundance of dominant bacterial phyla and genera in soil. Redundancy analysis and correlation analysis results also showed that there was a strong correlation between the removal rate of PAHs and dominant bacteria in the rhizosphere soil. The present study indicated that biochar could reduce dietary risk of PAHs in wheat grains mainly by increasing the abundance of bacteria related to PAHs degradation, promoting the biodegradation of PAHs in the rhizosphere soil and consequently reducing PAHs uptake in wheat.

Growth of winter wheat adapting to climate warming may face more low‐temperature damage

AbstractChina's surface air temperature is increasing due to global warming, so it is interesting that how low temperatures would be changed during the growth period of winter wheat in future. We focused on the low temperatures of winter wheat from 2021 to 2050, using temperatures under the high emission scenario Representative Concentration Pathway 8.5 (RCP8.5) projected by the RegCM4.4 regional climate model. The results showed that the annual mean temperature was projected to increase by 0.42°C⋅decade−1 in the northern and by 0.35°C⋅decade−1 in the southern winter wheat region. Furthermore, the temperature was expected to increase rapidly in spring, which could advance the dates of flowering and the start of the grain‐filling period. Using the genetic parameters determined by the calibration and validation of WOFOST and bias‐corrected projected meteorological data, simulations of winter wheat growth were performed over the winter wheat region for 2021–2050. The simulated number of days to the flowering period of winter wheat for 2041–2050 was on average 6.5 days less than in 2021–2030, due to the spring warming. Because of the earlier start of the growing season, winter wheat could face negative effects by being subjected to low temperatures. Indeed, the number of low‐temperature days was projected to increase by 110% from 2041 to 2050 compared to 2021–2030, and the number of killing degree days (KDDs) is projected to increase by 120% at the same time. If the number of days to flowering did not change, the number of low‐temperature days and KDDs only changed slightly, showing that the negative influence of low temperature was mainly caused by the advancement of the flowering date. The effect of low temperature on growth was underestimated when the response of winter wheat growth to global warming was not considered.

Tracking the influence of drought events on winter wheat using long-term gross primary production and yield in the Wei River Basin, China

The Wei River Basin (WRB) is the main winter wheat-producing area in Northwest China and plays a pivotal role in national food security and economic development. Drought is the main agro-meteorological disaster affecting winter wheat yield in this region, and the accurate assessment of the drought impacts on crop growth and yield is an important part of maintaining food security. However, commonly used assessment methods, such as correlation analysis and crop model simulation, have some limitations. In this study, based on standardized precipitation evapotranspiration index (SPEI) at multiple time scales, gross primary production (GPP) and yield data from 1990 to 2018, sensitivity analysis, Pearson correlation, and superposed epoch analysis (SEA) were used to analyze the spatiotemporal characteristics of drought in the WRB and its influence on winter wheat growth and quantitatively assess the impact of drought at different levels on winter wheat yield. The results were as follows: 1) Overall, the WRB was in a dry state with a drying trend during 1990–2018, and the droughts in spring, summer, and winter were the main driving forces of annual drought that seriously threatened the growth and yield of winter wheat, especially in spring (March–May), which is the key growth period of winter wheat. 2) The average annual GPP of winter wheat in the WRB showed a significant upward trend of 0.465 · 10a−1, and the central part of the WRB was the region where winter wheat GPP had higher sensitivity to drought. In general, winter wheat GPP during the growing season was most sensitive to SPEI-3, indicating that seasonal water deficits had the greatest impact on winter wheat growth. 3) The yield reduction of winter wheat caused by drought presented a spatial distribution that is heavy in the north and light in the south, and as the drought grade increased, the winter wheat yield decreased more significantly, even in irrigated areas. Therefore, relevant government departments still need to strengthen the risk management of agricultural droughts in the WRB and formulate reasonable policies to maintain food security.

Effect of Border Width and Micro-Sprinkling Hose Irrigation on Soil Moisture Distribution and Irrigation Quality for Wheat Crops

Micro-sprinkling irrigation is a small-flow irrigation technology that uses the grouped outlets on the micro-sprinkling hoses to spray the pressure water evenly in the field. Plants’ barriers during the middle to late growth period of winter wheat significantly reduce the irrigation quality of the micro-spray system. It is still unclear whether soil border width in wheat fields can alleviate the negative effect. In this study, a popularly-used variety (c.v. ZM 369) was adopted to test the mitigation effect of soil borders on irrigation quality, as well as soil moisture distribution, in wheat fields. Two irrigation quotas (i.e., 75 mm and 45 mm per time) and three border widths (i.e., 2.3 m, 3.3 m, and 5.3 m) were arranged in a randomized block design in the experimental years of 2020–2022. Soil moisture distribution and irrigation quality during the middle to late growth period of winter wheat (i.e., jointing to heading stage and grain filling stage) were investigated, as well as the effects on grain yield and water use efficiency (WUE). The results showed that irrigation water distribution in the direction perpendicular to micro-spray tapes generally decreased with the distance from tapes increasing. The maximum difference between the irrigation amount and water collected under the canopy was 134 mm. The uniformity coefficient of soil moisture distribution was increased by 25.8% with a 5.3 m border width compared to a 2.3 m width. Although an irrigation quota of 75 mm was beneficial for ensuring better irrigation uniformity and more stable grain yield, grain yield and WUE were produced with an irrigation quota of 45 mm. In conclusion, it is appropriate to increase border width and adopt a small quota for the micro-spray system in the North China Plain for wheat crops.

Good harvests of winter wheat from stored soil water and improved temperature during fallow period by plastic film mulching

Plastic film mulching (FM) has been widely used to increase wheat yield in arid and semiarid regions. However, most researchers have focused on FM during the growth period of winter wheat; as such, a knowledge gap remains regarding FM in other periods. Accordingly, we established a long−term field experiment in 2002 that included four treatments on the Loess Plateau of China. These four treatments included the following: regular fertilization without film (NP), regular fertilization with FM in the fallow period (NPFF), regular fertilization with FM in the growth period (NPFG), regular fertilization with FM for the whole year (NPFW). In 2020 − 2021, we measured the soil water distribution and root distribution in the 0 − 200 cm profile; the soil temperature in 5, 15, 30, and 50 cm soil layers; the winter wheat grain yield; the water use efficiency (WUE); and rainfall use efficiency (RUE). Our results demonstrated that compared with NP, the winter wheat yield of NPFF, NPFG, and NPFW improved by 37.1%, 7.8%, and 21.3% (p < 0.05). The WUE of NPFF, NPFG, and NPFW was 29.5%, 14.3%, and 12.5% higher than NP. Additionally, the RUE of NPFF, NPFG, and NPFW was 37.8%, 8.9%, and 22.2% higher than NP. The profile’s annual average soil temperature of NPFF, NPFG, and NPFW were 0.6 °C, 1.0 °C, and 1.4 °C higher than NP. Further, the root mass of NPFF, NPFG, and NPFW were 16.7%, 41.7%, and 8.3% higher than NP, respectively, and the root mass percentage of NPFF, NPFG, and NPFW decreased significantly by 7.3%, 6.0%, and 24.8% less than NP, respectively, in the 0 − 40 cm soil layer (p < 0.05). In sum, FM during the fallow period was considered an appropriate yield increase measure on the Loess Plateau of China and similar regions because of its advantages in collecting precipitation during the fallow period, regulating wheat growth temperature, and obtaining high yields.

A Drought Index: The Standardized Precipitation Evapotranspiration Irrigation Index

Drought has had an increasingly serious impact on humans with global climate change. The drought index is an important indicator used to understand and assess different types of droughts. At present, many drought indexes do not sufficiently consider human activity factors. This study presents a modified drought index and the standardized precipitation evapotranspiration irrigation index (SPEII), considering the human activity of irrigation that is based on the theory of the standardized precipitation evapotranspiration index (SPEI). This study aims to compare the modified drought index (SPEII) and ·SPEI and self-calibrating Palmer drought severity index (scPDSI) in the major crop-producing areas and use SPEII to evaluate the possible future drought characteristics based on CMIP5 Model. The Pearson correlation coefficient was used to assess the relevance between drought indexes (SPEII, SPEI, and scPDSI) and vegetation dynamics. The normalized difference vegetation index (NDVI) was used to represent the vegetation dynamics change. The results showed that SPEII had better performance than the SPEI and scPDSI in monitoring cropland vegetation drought, especially in cropland areas with high irrigation. The winter wheat growth period of the SPEII had better performance than that of summer maize in croplands with higher irrigation levels on the North China Plain (NCP) and Loess Plateau (LP). In general, future drought on the NCP and LP showed small changes compared with the base period (2001–2007). The drought intensity of the winter wheat growth period showed an increasing and steady trend in 2020–2080 under the representative concentration pathway (RCP) 4.5 scenario on the NCP and LP; additionally, the severe drought frequency in the central LP showed an increasing trend between 2020 and 2059. Therefore, the SPEII can be more suitable for analyzing and evaluating drought conditions in a large area of irrigated cropland and to assess the impacts of climate change on vegetation.

Simulation modeling for effective management of irrigation water for winter wheat

Lack of water resources, low irrigation efficiency, and inappropriate irrigation decisions severely restrict agricultural production in arid and semi-arid regions. Therefore, rapid and accurate decision-making regarding crop irrigation in real time is necessary. This study optimized irrigation scheduling by using information on different meteorological years and obtained the average soil water content (0–60 cm) before each irrigation, the corresponding irrigation time, and the water available for irrigation. The relative development speed of winter wheat and the amount of water available for irrigation were considered, and a dynamic irrigation water limit model was constructed. Winter wheat field experiments over 3 years (2016–2019) were followed by an evaluation of the regional applicability of the decision support system for the agrotechnology transfer model. A long short-term memory network effectively predicted air temperature and solar radiation; the R2 and root mean square error values were 0.802–0.964% and 12.53–23.9%, respectively. Public weather forecasts can be used to accurately predict rainfall, with 87.3% and 57% accuracy rates for forecasts of no rain and rain, respectively. Compared with traditional irrigation, the use of this dynamic irrigation lower limit for irrigation forecasting can increase yield and attendant net benefits. When two and three irrigation treatments were applied during the winter wheat growth period, the 3-year average yield increased by 10.3% and 4.4%, respectively, and the net benefit increased by 19.1% and 7.4%, respectively. The proposed method avoids relying on only field experiments to determine the irrigation lower limit and allows for the effective implementation of optimized irrigation schedules and the dynamic correction of irrigation plans in arid and semi-arid areas.

Application of Cosmic-Ray Neutron Sensor Method to Calculate Field Water Use Efficiency

Field water use efficiency is an important parameter for evaluating the quality of field irrigation in irrigated areas, which directly affects the country’s food security and water resource allocation. However, most current studies use point-scale soil moisture (SM) or remote sensing water balance models to calculate the field water use coefficient, which cannot avoid errors caused by the spatial heterogeneity of SM and insufficient spatial resolution of remote sensing data. Therefore, in this study, the cosmic-ray neutron sensor (CRNS), Time-Domain Reflectometers (TDR) and Automatic Weather Stations (AWS) were used to monitor the meteorological and hydrological data such as SM, atmospheric pressure, and precipitation in the experimental area of Jinghuiqu Irrigation District for three consecutive years. The scale of the CRNS SM lies between the point and the remote sensing. Based on the CRNS SM, the calculation method for canal head and tail water was used to calculate the field water use efficiency to evaluate the level of agricultural irrigation water use in the experimental irrigation area. The results showed that CRNS could accurately detect the change in SM, and four irrigation events were monitored during the winter wheat growth period from October 2018 to June 2019; the calculation result of field water use efficiency in the experimental area was 0.77. According to the field water use efficiency of the same irrigation area from October 2013 to October 2015 in other studies, the field water use efficiency during the growing period of winter wheat in this area increased from 0.503 to 0.770 in 2013–2019, indicating a significant improvement in the field water use level. In general, this study not only solves the problem of low calculation accuracy of field water use efficiency caused by the mismatch of SM monitoring scales but also explores the application potential of CRNS in agricultural irrigation management and water resource allocation.

Effects of warming and drought stress on winter wheat in Jiangsu Province, China

AbstractWe used the World Food Studies (WOFOST) model to analyze meteorological, soil, and winter wheat (Triticum aestivum L.) growth period data in Xuzhou, Huaian, and Changzhou, Jiangsu Province from 2008 to 2017. The data collected were used to study the effects of warming and drought on winter wheat yield and dry matter accumulation. The simulation results showed that single warming stress (1, 2, and 3 ℃), drought stress (mild, moderate, and severe), and combined drought and warming stress can reduce the yield of winter wheat. The highest yield reduction rate was 25.5% in Changzhou under the condition of single warming, and the yield reduction rate increased by 5% when the soil relative humidity decreased by 10% under the condition of single drought. The grain dry matter formation of winter wheat was also inhibited by warming and drought, and the lowest dry matter ratio was only 42.4% in Changzhou under drought. The influence of combined stress was greater than that of single stress under various contrasts. However, in the middle of Jiangsu Province, the yield of winter wheat was most affected by drought, and the distribution of dry matter accumulation decreased from south to north. The yield reduction of winter wheat under other stresses increased from south to north, and the dry matter distribution of grain was lower in the south than in the north and lower in the central part of Jiangsu Province.