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Wheat, rice, and maize collectively provide the bulk of energy and protein to the human diet worldwide. Over the last seven decades, China increased 5.8-fold the aggregated production of the three cereals, but further gains are required to meet the predicted demand of 776 Mt. by 2030. Here, we report the rate of genetic gain in yield of 0.65% year-1 for wheat between 1937 and 2012, 0.69% year-1 for rice between 1934 and 2011, and 0.77% year-1 for maize between 1950 and 2014 in China. National farm yield in the same periods increased 1.38% year-1 for wheat, 1.15% year-1 for rice and 1.32% year-1 for maize. Hence, genetic improvement (G) accounted for 47%-60% of the increase in farm yield, with improved management (M) and G × M interaction accounting for the balance. The absolute rate of genetic gain (kg ha-1 year-1) was proportional to environmental potential. Genetic gain in nitrogen utilization efficiency (yield per unit nitrogen uptake) was significant for all three crops and was achieved at the expense in grain N concentration that decreased at 0.19% year-1 in rice and 0.47% year-1 in maize. To guarantee future food security and environmental sustainability, breeding and agronomic efforts need to increase the rate of gain in yield and revert the declining trends in grain protein by improving nitrogen uptake and nitrogen harvest index. [ABSTRACT FROM AUTHOR]

• Defoliation was largely neutral for grain yield and WUE. • Defoliation improved harvest index and net income by 7–15%. • Defoliation improved translocation of WSC to grain. • Dual-purpose wheat was more profitable at low seeding rate and high initial soil water. Dual-purpose wheat has been adopted in many farming systems, but interactions between management, supply of resources, and seasonal conditions are still not clearly elucidated. Two experiments were established in the Loess Plateau of China to measure yield and its components, evapotranspiration, water-use efficiency (yield per unit evapotranspiration), accumulation and apparent remobilisation of stem water soluble carbohydrates (WSC), and economic benefit of dual-purpose winter wheat. Experiment 1 combined factorially three defoliation treatments, i.e. winter defoliation (DC23), spring defoliation (DC29) and untreated control, two seeding rates (currently recommended, and 125% recommended), and over four seasons. Experiment 2 combined factorially two defoliation treatments (spring defoliation and control), two nitrogen rates (low: 120–150 kg N ha−1, high: 180–200 kg N ha−1), three levels of soil water at sowing (low: rainfed; medium: rain +67 mm; high: rain +133 mm), and over three seasons. Defoliation was largely neutral for grain yield and water-use efficiency, and improved translocation of WSC to grain by 8%, harvest index by 7% and net income by 15% across conditions. Grain yield was unaffected by the interaction between defoliation and seeding rate, but significantly impacted by interactions of defoliation × initial soil water level and defoliation × nitrogen rate. Defoliated wheat yield was greater at high than at medium and low initial soil water content, and at low than at high nitrogen rate. Spring defoliation produced similar yield as winter defoliation but the former increased forage income. Increasing seeding rate or nitrogen rate increased forage income but reduced net income due to lower grain income and higher cost. Thus, dual-purpose winter wheat was more profitable (i) when defoliated in spring, (ii) at the lower seeding density, (iii) under the lower nitrogen rate, and (iv) with higher soil water content at sowing. Apparent translocation of stem WSC partially mediated the effect of defoliation on grain yield. It is concluded that dual-purpose winter wheat is feasible under straw mulching in semiarid environment. [ABSTRACT FROM AUTHOR]

Driven by a national commitment to achieve food security in China, policies have unintentionally favored overfertilization, with implications for the environmentally concerning release of reactive nitrogen (N r) and greenhouse gas (GHG) emissions. We assessed current winter wheat yield, protein concentration, N r losses, GHG emissions, and net profit in the winter wheat–summer fallow system in the Loess Plateau of China, using a combination of (i) original data from a 14-year field experiment, including five N fertilizer rates from unfertilized control to 320 kg N ha–1, (ii) surveys from 1167 farmers, and (iii) modeling. The study emphasized on N, with a secondary focus on phosphorus (P) and potassium (K). Farmer yields ranged from 1500 to 13,500 kg ha–1, and fertilizer rates ranged from 0 to 465 kg N ha–1, 0–454 kg P 2 O 5 ha–1, and 0–279 kg K 2 O ha–1. Five yield scenarios were compared: (1) Y max , defined as the maximum from the yield–N rate curve; (2) Y uptake , defined as the yield when N application rate equaled N uptake; and (3) low, (4) moderate and (5) high yields in farms. The yield–N rate curve accounted for summer rainfall, with Y uptake expected to return smaller environmental impacts than Y max. Compared with Y max , targeting Y uptake would reduce N fertilizer rate (40%), N r losses (25%), and GHG emissions (14%), with modest reductions in yield (7%), protein concentration (6%), and net profit (11%). Compared with current practice, Y uptake would increase net profit (140%) and decrease N r losses (23%) and GHG emissions (14%). Scaling to the Loess Plateau region (246.3 × 104 ha wheat-growing area), targeting Y uptake would return a production of 1.4 × 107 t yr–1 and increase annual net profit by US$7.3 × 108 with less N r losses (17,200 Mg) and GHG emissions (1.2 × 106 Mg CO 2 eq) in relation to farmer practice. Therefore, targeting Y uptake and matching NPK fertilization to summer rainfall should be adopted to improve wheat yield and net profit and reduce environmental risk in the Loess Plateau and similar regions. [Display omitted] • Five yield scenarios were modeled using data from a field experiment and farm survey. • Yield, protein, N r losses, GHG emissions, and net profit were compared between scenarios. • Promoting fertilization accounting for summer rainfall and crop N uptake were recommended. • Targeting Y uptake reduced N r (23%) and GHG (14%) compared to current practice. [ABSTRACT FROM AUTHOR]