为理解长期有机物料与化学氮肥配施对土壤有机碳和全氮的影响，在黄淮海平原开展了长达30年的小麦-玉米轮作田间试验（1990–2019年）。试验包含5个施肥处理：不施肥（control）、单施化肥（NPK）、化肥与秸秆配施（NPKS）、化肥与有机肥配施（NPKM）和1.5倍化肥与有机肥配施（1.5NPKM），NPK、NPKS和NPKM处理氮投入总量相同。测定试验期间作物产量，采集土壤表层(0–10 and 10–20 cm)和下层(20–40 cm)样品，进行土壤团聚体分级并测定团聚体碳氮含量。有机无机配合处理（NPKS, NPKM和1.5NPKM）与NPK处理相比，30年平均作物产量无显著差异，土壤表层和下层有机碳和全氮均显著提高，表层土壤有机碳和全氮分别提高24.1–44.4%和22.8–47.7%，下层土壤有机碳和全氮分别提高22.0–47.9%和19.8–41.8%%。与NPK处理相比，NPKS处理0-10cm土层和NPKM处理20-40cm土层具有显著较高的大团聚体组分质量比例，提高幅度分别为19.8和27.0%；然而，1.5NPKM处理在0-10cm和20-40cm土层的土壤大团聚体组分质量比例较对照显著降低，下降幅度分别为-19.2和-29.1%。分析表明有机无机配合处理较NPK处理有显著较高土壤有机碳和全氮主要与自由态微团聚体和大团聚体中的微团聚体等土壤稳定性组分的碳氮增加有关，稳定性组分对土壤碳氮含量增加的贡献率分别达81.1–91.7%和 83.3–94.0%。不同施肥处理0-40cm土层的土壤稳定性碳库和氮库与处理年平均碳投入量均呈显著正相关，回归系数分别为0.74和0.72（P<0.01），表明土壤氮对碳贮存的重要性。我们研究为长期有机物料与化学氮肥配施措施在保持合理总氮投入下有利于上层和下层土壤碳氮的保蓄提供了证据。

了解磷组分特征和影响因素对提高土壤磷利用效率具有重要的意义。基于黑土、潮土和塿土的长期定位试验，选择了五种施肥方式并将其分为三组：无磷肥处理（CK/NK）、平衡施用无机肥处理（NPK/NPKS）和有机无机配施处理（NPKM）。对土壤无机磷组分和土壤性质进行了分析，研究了无机磷组分特征及无机磷组分与土壤性质的关系。结果表明，三种土壤中Ca₁₀-P占总无机磷的比例最高，黑土、潮土和塿土分别为33.5%、48.8%、44.8%。长期施肥导致了土壤无机磷累积或耗竭的周期性变化。NPK/NPKS和NPKM处理下，黑土和潮土在施肥后期（10-20年）的磷累积量高于施肥早期（0-10年），而塿土正好相反。黑土中无机磷的累积发生在全部磷组分中，而潮土主要为Ca₈-P、Fe-P和Ca₁₀-P，塿土主要为Ca₂-P、Ca₈-P和O-P。CK/NK处理下，三种土壤的无机磷耗竭主要发生在施肥早期；除活性无机磷（Ca₂-P）和中活性无机磷（Ca₈-P、Fe-P、Al-P）外，黑土和潮土中的Ca₁₀-P，塿土中的O-P也可被作物利用。冗余分析表明，土壤性质解释了每种土壤90%以上无机磷组分的变化，其中，土壤有机质的解释百分比在黑土、潮土和塿土中分别为43.6%、74.6%、38.2%。总之，在非酸性土壤中施用磷肥时，应考虑磷的累积速率和土壤性质驱动的无机磷组分的变化。

Soil productivity (SP) without external fertilization influence is an important indicator for the capacity of a soil to support crop yield. However, there have been difficulties in estimating values of SPs for soils after various long-term field treatments because the treatment without external fertilization is used but is depleted in soil nutrients, leading to erroneous estimation. The objectives of this study were to estimate the change of SP across different cropping seasons using pot experiments, and to evaluate the steady SP value (which is defined by the basal contribution of soil itself to crop yield) after various longterm fertilization treatments in soils at different geographical locations. The pot experiments were conducted in Jinxian of Jiangxi Province with paddy soil, Zhengzhou of Henan Province with fluvo-aquic soil, and Gongzhuling of Jilin Province with black soils, China. Soils were collected after long-term field fertilization treatments of no fertilizer (control; CK-F), chemical fertilizer (NPK-F), and combined chemical fertilizer with manure (NPKM-F). The soils received either no fertilizer (F0) or chemical fertilizer (F1) for 3–6 cropping seasons in pots, which include CK-P (control; no fertilizer from long-term field experiments for pot experiments), NPK-P (chemical fertilizer from long-term field experiments for pot experiments), and NPKM-P (combined chemical and organic fertilizers from long-term field experiments for pot experiments). The yield data were used to calculate SP values. The initial SP values were high, but decreased rapidly until a relatively steady SP was achieved at or after about three cropping seasons for paddy and fluvo-aquic soils. The steady SP values in the third cropping season from CK-P, NPK-P, and NPKM-P treatments were 37.7, 44.1, and 50.0% in the paddy soil, 34.2, 38.1, and 50.0% in the fluvo-aquic soil, with the highest value observed in the NPKM-P treatment for all soils. However, further research is required in the black soils to incorporate more than three cropping seasons. The partial least squares path mode (PLS-PM) showed that total N (nitrogen) and C/N ratio (the ratio of soil organic carbon and total N) had positive effects on the steady SP for all three soils. These findings confirm the significance of the incorporation of manure for attaining high soil productivity. Regulation of the soil C/N ratio was the other main factor for steady SP through fertilization management.

In order to reveal the impact of various fertilization strategies on carbon (C) and nitrogen (N) accumulation and allocation in corn (Zea mays L.), corn was grown in the fields where continuous fertilization management had been lasted about 18 years at two sites located in Central and Northeast China (Zhengzhou and Gongzhuling), and biomass C and N contents in different organs of corn at harvest were analyzed. The fertilization treatments included non-fertilizer (control), chemical fertilizers of either nitrogen (N), or nitrogen and phosphorus (NP), or phosphorus and potassium (PK), or nitrogen, phosphorus and potassium (NPK), NPK plus manure (NPKM), 150% of the NPKM (1.5NPKM), and NPK plus straw (NPKS). The results showed that accumulated C in aboveground ranged from 2 550–5 630 kg ha–1 in the control treatment to 9 300–9 610 kg ha–1 in the NPKM treatment, of which 57–67% and 43–50% were allocated in the non-grain organs, respectively. Accumulated N in aboveground ranged from 44.8–55.2 kg ha–1 in the control treatment to 211–222 kg ha–1 in the NPKM treatment, of which 35–48% and 33–44% were allocated in the non-grain parts, respectively. C allocated to stem and leaf for the PK treatment was 65 and 49% higher than that for the NPKM treatment at the both sites, respectively, while N allocated to the organs for the PK treatment was 18 and 6% higher than that for the NPKM treatment, respectively. This study demonstrated that responses of C and N allocation in corn to fertilization strategies were different, and C allocation was more sensitive to fertilization treatments than N allocation in the area.

The improvement of soil productivity depends on a rational input of water and nutrients, optimal field management, and the increase of basic soil productivity (BSP). In this study, BSP is defined as the productive capacity of a farmland soil with its own physical and chemical properties for a specific crop season under local field management. Based on 19-yr data of the long-term agronomic experiments (1989–2008) on a fluvo-aquic soil in Zhengzhou, Henan Province, China, the decision support system for agrotechnology transfer (DSSAT ver. 4.0) crop growth model was used to simulate yields by BSP of winter wheat (Triticum aestivium L.) and summer maize (Zea mays L.) to examine the relationship between BSP and soil organic carbon (SOC) under long-term fertilization. Five treatments were included: (1) no fertilization (control), (2) nitrogen, phosphorus and potassium fertilizers (NPK), (3) NPK plus manure (NPKM), (4) 1.5 times of NPKM (1.5NPKM), and (5) NPK plus straw (NPKS). After 19 yr of treatments, the SOC stock increased 16.7, 44.2, 69.9, and 25.2% under the NPK, NPKM, 1.5NPKM, and NPKS, respectively, compared to the initial value. Among various nutrient factors affecting contribution percentage of BSP to winter wheat and summer maize, SOC was a major affecting factor for BSP in the fluvo-aquic soil. There were significant positive correlations between SOC stock and yields by BSP of winter wheat and summer maize (P<0.01), and yields by BSP of winter wheat and summer maize increased 154 and 132 kg ha–1 when SOC stock increased 1 t C ha–1. Thus, increased SOC accumulation is a crucial way for increasing BSP in fluvo-aquic soil. The manure or straw combined application with chemical fertilizers significantly enhanced BSP compared to the application of chemical fertilizers alone.

A 2-yr field experiment was conducted on a calcareous alluvial soil with four summer maize intercropping systems at Shangzhuang Experiment Station (116.3°E, 39.9°N) in the North China Plain. The objective was to determine nitrate leaching from intercropping systems involving maize (Zea mays L.): sole maize (CK), maize + soybean (CST), maize + groundnut (CGT), maize+ ryegrass (CHM), and maize + alfalfa (CMX). Intercropping greatly reduced nitrate accumulation in the 100-200 cm soil layers compared with maize monoculture. Nitrate accumulation under intercropping systems decreased significantly at the 140-200 cm soil depth; the accumulation varied in the order CK>CST>CMX>CHM>CGT. However, compared to the CK treatment, nitrate leaching losses during the maize growing period were reduced by 20.9- 174.8 (CGT), 35.2-130.8 (CHM), 60.4-122.0 (CMX), and 30.6-82.4 kg ha-1 (CST). The results also suggested that intercropping is an effective way to reduce nitrogen leaching in fields with N fertilizer over-dose.