Although conservation tillage has been widely implemented to address the challenge to improve crop yield and soil quality with fewer environmental costs, its long-term effects on crop yields and soil stoichiometry balance remain uncertain. Here, four different long-term (17-year) tillage practices (conventional tillage (CT), deep scarification (DS), no tillage (NT), and ridge tillage (RT)) were conducted in northern China to evaluate their effects on crop yield, soil nutrients, C sequestration, and soil stoichiometry. The conservation tillage (DS, NT, and RT) increased the recent 5-year average yields by 12.2 %-20.1 % compared with CT, respectively. RT showed the highest C sequestration potential of 10.0 t/ha, followed by DS and NT (6.0 t/ha and 4.4 t/ha, respectively). The DS, NT, and RT enhanced soil available N and K with the best effect for NT, but DS reduced soil total and available P. The conservation tillage significantly increased the C:N, C:P, C:K, and N:P ratios, indicating it sustained soil balanced stoichiometry. Correlation analysis indicated crop yield was closely related to soil C:N, C:P, C:K, and N:P. The structural equation model revealed that the C, N, and P affected C:N and C:P ratios, thus improving crop yield under long-term conservation tillage. In summary, long-term conservation tillage improves soil stoichiometry balance and thus crop yields with great C sequestration potential to achieve sustainable agricultural management in rain-fed farmland.

The performance of fertilizers may differ significantly in different soils. Here, we quantify effects of various phosphorus (P) fertilizers on maize yield and P uptake in soils with different pH values, using a pot experiment. Five P fertilizers were used; monoammonium phosphate (MAP), diammonium phosphate (DAP), calcium superphosphate (CSP), calcium magnesium phosphate (CMP) and, ammonium polyphosphate (APP). Two soils were neutral fluvo-aquic soil (pH 7.2) and acidic yellow cinnamon soil (pH 5.0). Generally, acidic soil restricted the root activity, dry matter accumulation, P uptake, and yield of maize. The effects of P fertilizers were inconsistent in the different soils. In neutral soil, the effects were the highest for DAP and lowest for CMP. However, in acidic soil they were highest for CMP, followed by DAP, and lowest for MAP. In neutral soil, DAP treatment showed higher P uptake efficiency (PUpE) and partial factor productivity (PPFP), while CMP treatment showed higher P harvest index (PHI) and utilization efficiency PUtE. In acidic soil, the PUpE and PPFP of CMP and DAP treatments were higher than in other treatments. Therefore, choosing the right P fertilizer based on soil acidity can significantly improve maize yield, P uptake, and P utilization to optimize P management.

Inadequate water and nitrogen (N) supplies can limit the productivity of maize. Climate change will likely increase drought in many regions on a global scale. The determination of N fertilizer rates under field drought conditions will be critical toward the reduction of agricultural risk. For this study, drought-resistant/sensitive cultivars were selected as experimental samples. Our results revealed that drought stress reduced the relative water content (RWC) of leaves, which resulted in leaf curling, while decreasing photosynthesis levels and N accumulation. In contrast to those without N treatments, the application of N significantly increased grain yields by 26.8% during the wet year but increased only by 5.4% during the dry year. Under the same N levels, the reduction in yield caused by drought increased with the increased application of N. This was because the application of the N fertilizer translated to increase the leaf area and transpiration, exacerbated the soil water loss and induced a leaf curling state in maize, which had deleterious effects on photosynthesis and N absorption. During the dry year, the yields of drought-sensitive cultivars were even less than those without the application of N. Compared with those of drought-sensitive cultivars, the RWCs of drought-resistant cultivars decreased more rapidly, and they entered the state of leaf curling earlier. Thus, N fertilizer inputs should be reduced, and the extent of N fertilization for drought-sensitive cultivars should be reduced even further.

The stay-green leaf phenotype is typically associated with increased yields and improved stress resistance in maize breeding, due to higher nitrogen (N) nutrient levels that prolong greenness. The application of N fertilizer can regulate the N status of plants, and furthermore, impact the photosynthetic rates of leaves at the productive stage; however, N deficiencies and N excesses will reduce maize yields. Consequently, it is necessary to develop N fertilizer management strategies for different types of stay-green maize. For this study, the senescent cultivar Lianchuang 808 (LC808), moderate-stay-green cultivar Zhengdan 958 (ZD958), and over stay-green cultivar Denghai 685 (DH685) were selected as experimental models. Our results revealed that yields of ZD958 were slightly higher than DH685 and notably improved over than LC808. Compared with a non-stay-green cultivar LC808, ZD958 and DH685 still maintained higher chlorophyll contents and cell activities following the silking stage, while efficiently slowing the senescence rate. The supply of N fertilizer significantly prolonged leaf greenness and delayed senescence for ZD958 and DH685; however, the effect was not obvious for LC808. The stem remobilization efficiency of N was higher in the moderate-stay-green cultivar ZD958, in contrast to LC808, while the transfer of leaf N was lower than LC808, which guaranteed high leaf N levels, and that sufficient N was transferred to grains in ZD958. To obtain the highest yields, the optimal N fertilizer rates were 228.1 kg hm⁻² for LC0808, 180 kg hm⁻² for ZD958, and 203.8 kg hm⁻² for DH685. In future, the selection of stay-green type crops might serve as an important agricultural strategy to reduce the quantity of N fertilizer and increase N efficiency.

Understanding the role of soil organic matter (SOM) in soil quality and subsequent crop yield and input requirements is useful for agricultural sustainability. SOM is widely considered to affect a wide range of soil properties, however, great uncertainty still remains in identifying the relationships between SOM and crop yield due to the difficulty in separating the effect of SOM from other yield-limiting factors. Based on 543 on-farm experiments, where paired treatments with and without NPK fertilizer were conducted during 2005–2009, we quantified the inherent soil productivity, fertilization effect, and their contribution to rice yield and further evaluated their relationships with SOM contents under a rice cropping system in the Sichuan Basin of China. The inherent soil productivity assessed by rice grain yield under no fertilization (Y-CK) was 5.8 t/ha, on average, and contributed 70% to the 8.3 t/ha of rice yield under NPK fertilization (Y-NPK) while the other 30% was from the fertilization effect (FE). No significant correlation between SOM content and Y-NPK was observed, however, SOM content positively related to Y-CK and its contribution to Y-NPK but negatively to FE and its contribution to Y-NPK, indicating an increased soil contribution but a decreased fertilizer contribution to rice yield with increasing SOM. There were significantly positive relationships between SOM and soil available N, P, and K, indicating the potential contribution of SOM to inherent soil productivity by supplying nutrients from mineralization. As a result, approaches for SOM accumulation are practical to improve the inherent soil productivity and thereafter maintain a high crop productivity with less dependence on chemical fertilizers, while fertilization recommendations need to be adjusted with the temporal and spatial SOM variation.

Improving the growth, lodging and yield of different density-resistance maize by optimising planting density and nitrogen fertilisation | Yanan Zhao, Yufang Huang, Shuai Li, Xu Chu, Youliang Ye | Agricultural Journals