Green manure is a promising, at least partial, substitution for chemical fertilizer in agriculture, especially for nitrogen (N), which in soil can be radically changed by exogenous input. However, it is not well understood how, after green manure incorporation, soil N changes coordinate with crop N uptake and consequently contribute to fertilizer reduction in a maize–green manure rotation. A four-year field study was performed consisting of (1) control, no fertilization; (2) F₁₀₀, recommended inorganic fertilization alone; (3) G, green manure incorporation alone; (4) F₇₀ + G (70% of F₁₀₀ plus G); (5) F₈₅ + G; and (6) F₁₀₀ + G. The results show that treatments with 15–30% reduction of inorganic fertilizer (i.e., F₇₀ + G and F₈₅ + G) had similar grain yield, dry matter (DM) accumulation, and N uptake as F₁₀₀ treatment. F₁₀₀ + G maize had 17% greater DM and 15% more N uptake at maturity relative to F₁₀₀. Of the five soil N fractions examined, dissolved organic N (DON) and mineral N (N_min) explained over 70% of the variation of maize DM and N accumulation. Partial least squares path modeling further revealed that soil N fractions had positive indirect effects on DM production through N uptake, which might be coordinated with improved DON and N_min status at both early and mid-late stages of maize growth. Overall, the results highlight enhanced maize production with reduced fertilizer inputs based on green manure incorporation in temperate regions.

Cultivation of green manure crops is important strategy for improving soil fertility in South China. Therefore, it is important to obtain plant varieties that can better accumulate nutrients during the green manuring phase. The present study evaluated the phosphorus (P) and potassium (K) uptake efficiencies of various winter leguminous species at two different sites. Varieties tested included six Chinese milk vetch cultivars (i.e., Minzi No.6, Ningbodaqiao, Wanzi No.1, Xiangzi No.1, Yijiangzi, and Yujiangdaye), as well as hairy vetch and common vetch, while ryegrass was planted as a control. All leguminous species showed higher ability for P and K absorption in the two sites compared to the ryegrass. Hairy vetch and common vetch performed better than all six Chinese milk vetch cultivars, and the highest biomass and P and K uptake capacities were observed in hairy vetch. Green manuring had different effects on soil enzymes. Phosphatase (87.0%) and leucine-aminopeptidase (163.8%) were increased by hairy vetch. β-glucosidase (143.4%) and N-acetyl-glucosaminidase (283.3%) were increased by Yijiangzi and Yujiangdaye, respectively, in Guangxi compared to the control. Xiangzi No.1 increased N-acetyl-glucosaminidase (352.6%), leucine-aminopeptidase (477.5%), phosphatase (591%), and β-glucosidase (786.0%) in Hunan compared to the ryegrass. Enzyme activities increased nutrient availability at both experimental sites. P and K uptake efficiencies significantly related with soil enzymes in Guangxi. It is suggested that hairy vetch has the largest capability for P and K uptake and might be a potential choice for improving P and K management in sustainable agriculture.

Peanut (Arachis hypogaea L.) is one of the most important crops produced worldwide. Peanut is the dominant crop in the typical upland red soil areas of China; however, phosphorus bioavailability in red soil is very low, which severely affects peanut production. To improve the phosphorus bioavailability, which substantially promotes the green development of peanut production, a peanut–green manure rotation field experiment was conducted with six treatments (milkvetch; radish; brassica rape; mustard rape; winter fallow and no-tillage), commencing in September 2017 in the red soil area of Jiangxi province, China. The results show that compared with no-tillage (NT) treatments, different green manure returning treatments had significant effects on soil pH, soil phosphorus components and available potassium content. The particulate phosphorus and soil available phosphorus contents in the green manure treatments were significantly higher than those in the winter fallow (WF) treatment. Compared with the WF treatment, the content of particulate phosphorous in brassica rape (BR), radish (R) and milkvetch (MV) treatments was significantly increased by 6.55%, 3.66% and 2.50%, respectively; the available phosphorus content in mustard rape (MR), BR, R and MV was significantly increased by 20.93%, 25.60%, 23.76% and 18.10%, respectively. In addition, the total phosphorus content of peanut shell in the MV and R treatment was significantly higher than that in the WF treatment, increasing by 33.47% and 60.66%, respectively. Compared with the WF treatment, the peanut biomass of MR, BR and R treatments increased significantly by 19.51%, 29.83% and 19.77%, respectively. The total phosphorus accumulation in all green manure treatments was higher than that in the WF treatment, and the MV treatment reached a significant level at 18.83%. Based on these results, the particulate phosphorus (PP) and available phosphorus were significantly affected by different green manure treatments; green manure amendment improves peanut phosphorus uptake. The use of green manure (especially milkvetch and brassica rape) can be recommended to improve phosphorus bioavailability and yield of peanut in red soil areas.

Stem node has been found to be a hub for controlling mineral nutrient distribution in gramineous plants. However, the characteristics of stem nodes associated with whole-plant carbon partitioning in maize (Zea mays L.) and their responses to nitrogen (N) availability remains elusive. Maize plants were grown in greenhouse under low to high N supply. Plant growth, sugar accumulation, and sugar transporters in nodes and leaves, as well as the anatomical structure of nodes, were investigated at vegetative phase. When compared to N-sufficient plants, low-N availability stunted growth and resulted in 49–64% less sugars in leaves, which was attributed to low photosynthesis or the accelerated carbon export, as evidenced by more ¹³C detected further below leaf tips. Invariably higher sugar concentrations were found in the stem nodes, rather than in the leaves across N treatments, indicating a crucial role of nodes in facilitating whole-plant carbon partitioning. More and smaller vascular bundles and phloem were observed in stem nodes of N-deficient plants, while higher sugar levels were found in the bottom nodes than in the upper ones. Low-N availability upregulated the gene expressions of sugar transporters, which putatively function in nodes such as ZmSWEETs and ZmSUTs at the bottom stem, but suppressed them in the upper ones, showing a developmental impact on node function. Further, greater activity of sugar transporters in the bottom nodes was associated with less sugars in leaves. Overall, these results highlighted that stem nodes may play an important role in facilitating long-distance sugar transport in maize.