Wheat (Triticum aestivum L.)/maize (Zea mays L.)/soybean (Glycine max L.) relay strip intercropping (W/M/S) system is commonly used by the smallholders in the Southwest of China. However, little known is how to manage phosphorus (P) to enhance P use efficiency of the W/M/S system and to mitigate P leaching that is a major source of pollution. Field experiments were carried out in 2011, 2012, and 2013 to test the impact of five P application rates on yield and P use efficiency of the W/M/S system. The study measured grain yield, shoot P uptake, apparent P recovery efficiency (PRE) and soil P content. A linear-plateau model was used to determine the critical P rate that maximizes gains in the indexes of system productivity. The results show that increase in P application rates aggrandized shoot P uptake and crops yields at threshold rates of 70 and 71.5 kg P ha^-1 respectively. With P application rates increasing, the W/M/S system decreased the PRE from 35.9% to 12.3% averaged over the three years. A rational P application rate, 72 kg P ha^-1, or an appropriate soil Olsen-P level, 19.1 mg kg^-1, drives the W/M/S system to maximize total grain yield while minimizing P surplus, as a result of the PRE up to 28.0%. We conclude that rational P application is an important approach for relay intercropping to produce high yield while mitigating P pollution and the rational P application-based integrated P fertilizer management is vital for sustainable intensification of agriculture in the Southwest of China.

Optimization of nitrogen (N) fertilizer application is essential to achieve higher crop yields at lower environmental costs. This study investigated the impacts of N application rates (0, 180, and 360 kg N ha⁻¹) on maize productivity, N use efficiency (NUE), NO₃⁻-N leaching, cumulative N₂O emissions, and N surplus in maize growing in the purple soil of Southwest China through a 2-year field study. The critical N rate balancing yield optimization with reduced NO₃⁻-N leaching and N₂O emissions was identified. The results showed that grain yield initially increased linearly and then stabilized with increasing N rates, while NUE significantly decreased. NO₃⁻-N leaching, N₂O emissions, and N surplus exhibited quadratic increase. Regression analysis indicated that 158–163 kg N ha⁻¹ achieved optimal yield while maintaining acceptable NO₃⁻-N leaching and N₂O emissions compared to 360 kg N ha⁻¹. This range also enhanced NUE and minimized soil N residue.

The fruits of kiwifruit are well known for their abundant nutritional value and health benefits, but kiwifruit vines are susceptible to environmental factors such as drought or waterlogging. Optimum substrate moisture content (SMC) can decrease cultivation costs and improve the quality of seedlings in soilless cultivation. To quantify the water requirements of kiwifruit seedlings, a greenhouse study was conducted to investigate the growth, antioxidant defense, and photosynthetic parameters of seedlings of Actinidia valvata Dunn at six levels of SMC (20%, 40%, 60%, 80%, 100%, and 120%). Results showed that shoot and root dry matter accumulation increased gradually with the increase in SMC from 20% to 100% and was lower at 120% SMC than at 100% SMC. Electrolyte leakage and malondialdehyde content were the lowest at 80% and 100% SMC. Antioxidant enzyme activities, including superoxide dismutase, peroxidase, and catalase, chlorophyll content, net photosynthetic rate, maximal quantum yield of PSII photochemistry, photosynthetic electron transfer rate, and actual quantum yield were the highest at 80% and 100% SMC, but there was no significant difference in these parameters between the two treatments (80% and 100% SMC). However, the shoot and root dry weights of seedlings at 100% SMC were 13.20% and 33.02% higher than those at 80% SMC, respectively. In summary, 100% SMC provided optimal water supply for the photosynthetic efficiency and dry matter accumulation of shoots and roots. The results are expected to be useful for the mass production of high-quality kiwifruit seedlings in greenhouse or nursery containers, with the potential to save water.