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While the relationship between crop yields and the environmental impacts of crop agriculture has been well‐documented, research on the relationship between farm size and the sustainability of cereal production is limited. Using survey data on 120 farms with both small‐ and large‐scale fields in Northeast China, this paper combines a life cycle assessment and the carbon‐based sustainability index (SI) algorithm to examine how maize productivity and agricultural inputs vary with farm size and to clarify how increasing farm size is correlated with energy use efficiency (EUE) and the SI. The results indicate that maize grain yield did not vary with farm size. Increasing farm size was shown to lead to reductions in the areal (per ha) rates of agro‐chemical inputs, energy depletion, and greenhouse gas emissions and increased in EUE and SI. Fertilizer‐ and fuel‐related agricultural inputs dominated the variations of EUE and SI. A scenario analysis indicates that, if farmers adopt a comprehensive management strategy (i.e., machines appropriate to farm size and recommended fertilizer application rates and crop management strategies), EUE and SI would increase by 68.5% (from 4.45 to 7.50) and 74.3% (from 10.1 to 17.6), respectively. Although increasing farm size could benefit maize sustainable production when matched with technical innovation and machinery coordination, supporting smallholder farmers to increase their resource use efficiency and sustainability is also key in China and other regions where smallholder farms comprise a large portion of the cropland area. [ABSTRACT FROM AUTHOR]

In recent years, China's crop production growth rate has decreased. This has provoked questions on whether the grain yields have reached their potential. Taking the North China Plain (NCP) as the study area, this study first simulated the potential yield of an irrigated maize crop with the WOFOST model, using daily weather data for 1960–2017. The yield gap was quantified for 1998–2017, and finally, the total potential maize production was estimated. The results indicate that during 1960–2017, the average potential yield for the region varied annually from 9.5 to 13.5 t ha−1, showing an obvious downward trend at a rate of 37.6 kg ha−1 per year. The long‐term mean potential yield at all 327 counties ranged from 9.9 to 13.7 t ha−1, increasing from south to north. The annual maize yield gap was between an average of 2.7–6.0 t ha−1 (29.0%–51.3%) of the potential yield for the NCP during 1998–2017. At county‐level, the yield gap varied between 1.9 and 7.8 t ha−1 and exceeded 5.0 t ha−1 for 99 counties (30.3% of all counties). Attainable yields can be increased by 0.1–5.2 t ha−1 at county‐level, and by 2.2 t ha−1 for the whole NCP, implying that the maize production has the potential to increase with 20.8 Mt. To increase maize production, the focus areas should be the southcentral NCP, which have a larger yield gap during 2012–2017. [ABSTRACT FROM AUTHOR]

Large quantities of fertilizers, mainly nitrogen (N), phosphorus (P), and potassium (K), are used in China's crop production; however, whether N, P, and K still limit yield under the current high input remains unknown. In addition, it is not clear whether magnesium (Mg) potentially limits crop production. To address these issues, a national survey of the soil nutrient status and farmers' fertilization practices was conducted in China to determine the soil N, P, K, and Mg status and current fertilization practices. In addition, various experiments, including optimized NPK (OPTNPK) and Mg fertilizer combined with OPTNPK (OPTNPK + Mg) in comparison with farmers' practices (FFP), were performed across China to identify the potential for reducing NPK application and the need for Mg application in crop production. The survey data from 2699 questionnaires indicated that (1) all soil samples were not deficient in NPK, but 73.0% were limited by Mg. (2) The average N, P (in P2O5), K (in K2O), and Mg (in MgO) balances were 422.6, 334.1, 326.3, and −22.6 kg ha−1, respectively. Only 15.7% of all farmers applied Mg fertilizer. (3) NPK fertilization can be reduced by an average of 28.8% without reducing the crop yield and quality. (4) For most crops, the application of Mg fertilizer increased the crop yield by 5.5–40.6% and improved the quality. However, different crops under different conditions had different responses to Mg fertilization. These results indicate that reduced NPK inputs and increased Mg inputs are equally important for the healthy development and sustainability of China's agriculture. [ABSTRACT FROM AUTHOR]

Grain self‐sufficiency (GSS) is gaining increased attention throughout the world, and this holds particularly true for China. This study, therefore, investigated spatial and temporal patterns of GSS at the county level in China from 1980s to the 2010s; then explored future GSS changes in the 2035s according to China's 2016 dietary nutrition guidelines, under the circumstances of maximum, average and minimum grain yield increase rate; and finally discussed the ability of a county to purchase grain to meet its demands. The results indicate that the number of counties with self‐insufficiency for total grain and ration decreased, and the amount of counties with high‐level self‐sufficiency for total grain and ration increased. However, the change in the number of counties with feed grain self‐insufficiency and high‐level self‐sufficiency is opposite to that of ration and total grain. Eastern China was characterised by high GSS of total grain, ration and feed grain. As for different kinds of grain, high level of GSS distributed in main grain producing areas, such as rice in south China, wheat in western China and Huang Huai Hai Plain, maize in north and northwest China and soybean in northeast China. Qinghai‐Tibet plateau has undergone poor food security in the last 30 years. In the 2035s, China's total GSS level and ration self‐sufficiency level will be improved under the maximum and average grain yield increase rate, whilst for feed grain, the self‐sufficiency level will be improved only under the maximum grain yield increase rate. The Qinghai‐Tibet plateau has always been a fragile area of food security. This study plays the vital function in understanding China's food security and contributes to the optimisation of agricultural production as well as the utilisation of both internal and external markets. [ABSTRACT FROM AUTHOR]

The effects of global warming on crop production have received great attention in recent years. However, inconsistent results have been obtained with regard to major crops such as rice and wheat in rice–wheat rotation systems of China. Therefore, we undertook a comprehensive meta‐analysis of literature data. The yield response to warming differed for rice and wheat in the rice–wheat rotation system. Overall, warming significantly increased wheat yield (by 4.8%) but significantly reduced rice yield (by 14.8%). A number of factors were responsible for these observations. For example, rice yield responses varied with the temperature increase, variety and nitrogen (N) rate. Of these, N was the most important variable influencing yield responses to warming. The yield loss for rice was lower at temperature increases of 0.40–1.40°C and at a high N rate than that at temperature increases of 1.60–2.49°C and at a low N rate, respectively. The yield loss of indica rice was lower than that of japonica rice. For wheat, however, yield responses to warming varied with the warming regime, ambient temperature, temperature increases, and CO2 concentrations. Of these factors, ambient temperature was the most important variable influencing yield in response to warming. Warming increased wheat yield at a mean growth season temperature ≤10°C, temperature increases of 0.80–1.50°C, and at ambient CO2 concentrations. In addition, either daytime warming or nighttime warming significantly increased wheat yield. However, all‐day warming had no effect on wheat yields. We conclude that global warming will benefit wheat production but result in a serious loss of rice yield in rice–wheat rotations in China. [ABSTRACT FROM AUTHOR]