The input of exogenous organic materials is an effective way to improve soil organic matter (SOM) content in cropland. The exploration of the impact of new organic materials such as woody peat on black soil fertility can provide an important reference for preventing the degradation of black soil in Northeast China. In this study, the effects of adding woody peat to SOM and the soil-integrated fertility of black cropland were studied by seven treatments (no organic matter addition, CK; crop straw returning, SR; decomposed straw addition, DS; organic manure addition, OM; 6 t/ha woody peat addition, LWP; 10.5 t/ha natural humus material addition, MWP; and 15 t/ha natural humus material addition, HWP). The results show that natural humus material additions (LWP, MWP, and HWP treatments) could significantly increase SOM (increased by 4.79~9.41 g/kg), labile SOM (increased by 2.49~4.52 g/kg), and recalcitrant SOM (increased by 2.13~6.39 g/kg) components, respectively. For comparison, traditional organic material inputs (SR, DS, and OM treatments) had no significant effect on SOM but induced an increase in the labile SOM component in the following year. This study also found that natural humus material additions could improve soil-integrated fertility in a year term, especially in promoting SOM accumulation. However, organic manure amendment showed both the advantage of increasing soil fertility slightly and the disadvantage of increasing soil salt sharply. In conclusion, compared with traditional exogenous organic materials, the natural humus material amendment technique can rapidly increase the total SOM quantity and its different stability components and has a great effect in improving the integrated fertility of black soil. Thus, it is of significance to further study the potential of natural humus material amendment in the fertility of black soil in future.

Active crop sensor-based precision nitrogen (N) management can significantly improve N use efficiency but generally does not increase crop yield. The objective of this research was to develop and evaluate an active canopy sensor-based precision rice management system in terms of grain yield and quality, N use efficiency, and lodging resistance as compared with farmer practice, regional optimum rice management system recommended by the extension service, and a chlorophyll meter-based precision rice management system. Two field experiments were conducted from 2011 to 2013 at Jiansanjiang Experiment Station of China Agricultural University in Heilongjiang, China, involving four rice management systems and two varieties (Kongyu 131 and Longjing 21). The results indicated that the canopy sensor-based precision rice management system significantly increased rice grain yield (by 9.4–13.5%) over the farmer practice while improving N use efficiency, grain quality, and lodging resistance. Compared with the already optimized regional optimum rice management system, in the cool weather year of 2011, the developed system decreased the N rate applied in Kongyu 131 by 12% and improved N use efficiency without inducing yield loss. In the warm weather year of 2013, the canopy sensor-based management system recommended an 8% higher N rate to be applied in Longjing 21 than the regional optimum rice management, which improved rice panicle number per unit area and eventually led to increased grain yield by over 10% and improved N use efficiency. More studies are needed to further test the developed active canopy sensor-based precision rice management system under more diverse on-farm conditions and further improve it using unmanned aerial vehicle or satellite remote sensing technologies for large-scale applications.

Soil acid–base status fundamentally regulates biogeochemical cycling and agroecosystem resilience by controlling nutrient solubility, cation exchange, and redox equilibria. However, the long-term evolution of soil pH and its spatial divergence under intensive agricultural expansion remain poorly quantified. Herein, we integrate three nationwide soil surveys (1980, 2012, 2018) encompassing over 190,000 cropland observations into a harmonized 1 km dataset to reconstruct four decades of soil pH change across China. National mean soil pH declined from 7.1 in 1980 to 6.7 in 2012 and 6.6 in 2018, revealing a sustained acidification trend. Nearly one quarter of neutral soils (pH 6.5–7.5) have shifted into acidic classes (<6.5) since 1980, reflecting widespread depletion of soil buffering capacity under intensive fertilization, high rainfall, and carbonate exhaustion. By integrating current pH conditions with standardized pH change rate, we delineate nine bidirectional soil pH risk zones that capture contrasting acidification and alkalization processes along climatic and edaphic gradients. Acidification-prone zones dominate humid southern croplands, whereas alkalization risk prevails in arid northern regions. Our results provide nationally consistent, grid-level evidence of soil acid–base evolution across nearly four decades, offering a quantitative foundation for region-specific soil management to sustain productivity and mitigate environmental risks.

How to quickly monitor the growth process of maize on a large scale is crucial for regional maize growth assessment, yield estimation, and farmland management. This article takes the Sanjiang Plain in Northeast China as the research area, which is the main grain production area in China. Using MODIS NDVI time series data and Savitzky Golay and Whittaker filtering techniques, a remote sensing extraction method for key growth stages of maize (i.e., jointing stage, tasseling stage, and maturity stage) was established. The spatiotemporal characteristics of these growth stages from 2003 to 2022 were analyzed, alongside their meteorological influences. Results show the Whittaker filter achieves high accuracy, with errors under 8 days. Jointing stages typically fall between June 9^th and June 25^th, tasseling stages between July 20^th and August 5^th, and maturity stages between September 13^th and September 29^th. From 2003 to 2022, jointing and tasseling stages advanced by 0.43 and 0.19 days/year, respectively, while the maturity stage was delayed by 0.38 days/year, indicating an extended growing season correlated with rising surface temperatures and precipitation in the preceding month. These findings offer theoretical and technical guidance for crop growth monitoring, yield assessment, and farmland management.

Northeast China’s black soil region serves as a critical cornerstone of national food security, yet accelerating soil degradation, characterized by declining soil organic matter (SOM) and rising bulk density (BD), threatens the productive capacity of its farmland. Understanding how soil physicochemical properties regulate crop yields in this ecologically heterogeneous landscape is essential for sustainable agricultural development. Here, 2916 soil samples from 201 counties across six ecological zones were analyzed in conjunction with county-level rice and maize yield records. Our findings revealed that crop yield determinants are fundamentally governed by regional resource endowment characteristics rather than uniform factors. In areas characterized by sandy soil texture, low precipitation (1.34 g cm⁻³) and alkaline soil conditions (pH > 7.0) constitute the primary constraints to productivity through restricting root development. Conversely, in regions with fertile mollisols and high baseline soil organic matter (SOM > 40 g kg⁻¹), nutrient dynamics emerge as the dominant yield-regulating factors. For volcanic soil landscapes with strong phosphorus fixation capacity, available phosphorus deficiency represents the critical bottleneck for maize production. Path analysis further demonstrates that BD and pH operate predominantly through indirect mechanisms, modulating SOM accumulation and nutrient cycling rather than directly constraining yield. Threshold analysis identified that BD exceeding 1.34 g cm⁻³ and SOM below 26 g kg⁻¹ markedly reduce productivity, while SOM levels above 40 g kg⁻¹ yield diminishing marginal returns. These findings advance our mechanistic understanding and provide scientific foundations for spatially differentiated soil conservation and precision nutrient management strategies essential for sustaining grain production capacity in northeast China’s black soil region.