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Quantitative understanding of how fertilizer N affects tiller development is essential for simultaneously achieving high yield and high N use efficiency in wheat (Triticum aestivum L.) production. A 3-yr field experiment was conducted on the North China Plain during 2015-2017, with winter wheat grown at five fertilizer N rates (0-300 kg ha −1 ). The highest grain yield (∼9 Mg ha −1 ) was obtained at the optimized N rate (on average 160 kg ha −1 , determined by subtracting the soil NO 3 − content from estimated N target values) and attributed to the high spike number, which was further contributed by the main stem (MS) and the fertile first tiller (T1). Greater N application than the optimized rate did not further increase grain yield but increased the biomass and N concentration of other tillers that were unproductive. The critical plant aboveground N concentrations (2.81% at stem elongation stage [Zadoks Growth Stage, GS 31] and 1.95% at anthesis (GS 64) and critical root-zone soil mineral N content (N min ) (74 kg ha −1 at GS 31 and 129 kg ha −1 at GS 64) for the attainable maximum stem number (1578 m −2 at GS 31 and 944 m −2 at GS 64) were quantified in this high-yieldingsystem. The critical plant aboveground N concentrations for achieving the maximal biomass of stem were also established to be 2.72% at GS 31 and 1.53% at GS 64, respectively. At these critical levels, the maximal biomass of MS and T1 were obtained without increasing the growth of the other tillers that were unproductive. Our results showed that high yield of winter wheat can be achieved by increasing the number of productive stems and the biomass per productive stem through optimizing the rootzone N min and plant N concentrations.

Transforming apple production to one with high yield and economic benefit but low environmental impact by improving P-use efficiency is an essential objective in China. However, the potential for multi-objective improvement for smallholders and the corresponding implications for horticultural practices are not fully appreciated. Survey data collected from 99 apple producers in Quzhou County of Bohai Bay Region were analyzed by the Pareto-based multi-objective optimization method to determine the potential of multi-objective improvement in apple production. With current practices, apple yield was 45 t ha−1, and the economic benefit was nearly 83,000 CNY ha−1 but with as much as 344 kg P ha−1 input mainly from chemical fertilizer and manure. P gray water footprint was up to 27,200 m3 ha−1 due to low P-use efficiency. However, Pareto-optimized production, yield, and economic benefit could be improved by 38% and 111%, respectively. With a concurrent improvement in P-use efficiency, P gray water footprint was reduced by 29%. Multi-objective optimization was achieved with integrated horticultural practices. The study indicated that multi-objective optimization could be achieved at a smallholder scale with realistic changes in integrated horticultural practices. These findings serve to improve the understanding of multi-objective optimization for smallholders, identify possible constraints, and contribute to the development of strategies for sustainable apple production.