Based on the positioning test in the black soil area of Northeast China, the Innovation Team of Saline-alkali Soils Amelioration of the Institute of Agricultural Resources and Regional Planning (IARRP) of the Chinese Academy of Agricultural Sciences (CAAS), and the Institute of Crop Cultivation and Farming, Heilongjiang Academy of Agricultural Sciences, proved that pelletized straw can be buried at 5 tons/mu for three consecutive years. The content of soil organic matter increased from 2.79% to 3.60%, an increase of 0.81 percentage points over three years, providing a new feasible technical approach for the conservation and rapid improvement of black soil fertility through returning straw to the field in degraded black soil areas of Northeast China.

The relevant research results were published in Soil & Tillage Research under the title "Annual burying of straw after pelletizing: A novel and feasible way to improve soil fertility and productivity in Northeast China".

Compared with the non-returning of straw, returning chopped straw in a high amount (5 tons/mu) and constant amount (1 ton/mu) has the effect of soil fertilization, but there is a risk of yield reduction: it is difficult to coordinate soil fertilization and the crop yield increase contradiction. This is the main issue that restricts farmers from voluntarily implementing straw returning to the field.

Returning a large amount of pelletized straw to the field can significantly increase soil carbon and nitrogen content, balance soil nutrients, and reduce soil bulk density. Compared with not returning straw, the total carbon content of the surface layer (0-20 cm) and sub-surface layer (20-40 cm) increased by 14% and 51%, respectively, and the total nitrogen content increased by 9% and 42%, respectively. Soil carbon and nitrogen are relatively balanced.

In addition, compared with the non-returning of straw and the constant returning of chopped straw, returning a high amount of pelletized straw can reduce the surface soil bulk density by 8-14%. The large-amount deep burial and return of pelletized straw year after year can effectively increase the soil carbon and nitrogen content, thereby enhancing the greenness of maize leaves in the late growth stage, prolonging the filling period, increasing the number of grains per spike and the weight of 100-grain seeds, and increasing production and income. As the test period increases, the effect of increasing production is more obvious.

Specifically, compared with the non-returning of straw and the constant returning of chopped straw, returning large-amount pelletized straw can increase grain yield by 5-7% and 6-21% in the second and third years, respectively; compared with the same amount of chopped straw, returning a high amount of pelletized straw to the field can increase the yield by 5-28% in the first to third years.

Fig. 1 The effect of large-amount deep burial of pelletized straw returning to the field to soil improvement and yield increase

Fig. 2 Aerial photo of maize in the late grain-filling stage in the third year of large-amount pelletized straw buried and returned to the field (September 18, 2021)

Postdoctoral Wang Xiquan of the IARRP is the first author, and researcher Pang Huancheng is the corresponding author. This research was supported by the National Key Research and Development Program (2022YFD1500304), the National Natural Science Foundation of China (32172126), the Science and Technology Innovation Project of the Chinese Academy of Agricultural Sciences (CAAS-ZDRW202202) and the Natural Science Foundation of Heilongjiang Province (ZD2022C008).

Paper link: 

https://www.sciencedirect.com/science/article/pii/S0167198723000661?dgcid="author#fig0040