Distribution of Wheat and Maize Straw Resources in Shandong Province and Fertilizer Reduction Potential Under Straw Return

Shandong Province is the main wheat and maize producing province in North China. Clarifying the spatial distribution characteristics of wheat and maize straw resources and nutrient substitution potential of straw return of this province could provide the decision support for comprehensive utilization of crop straw and fertilizer reduction.

In this research, the wheat and maize straw yield and substitution potential of nutrient by straw return in different areas of Shandong Province were estimated by straw-to-grain ratio method, based on statistic yearbook data and published literature review.

The annual outputs of wheat and maize straw were 29.28 and 22.52 million tons, respectively, in Shandong Province during 2019-2021. The proportions of wheat and maize straw resources in different regions were ranked as follows: North Shandong (34.9% and 34.7%)>Southwest Shandong (27.6% and 24.9%)>Central Shandong (20.2% and 21.4%)>East Shandong (9.1% and 11.3%)>Southeast Shandong (8.2% and 7.8%). The order of collectable wheat straw per unit area was North Shandong (5 573 kg·hm^-2)>Southwest Shandong (5 380 kg·hm^-2)>Central Shandong (5 361 kg·hm^-2)>Southeast Shandong (5 088 kg·hm^-2)>East Shandong (4 968 kg·hm^-2). The order of collectable maize straw per unit area was Southwest Shandong (5 121 kg·hm^-2)>North Shandong (5 034 kg·hm^-2)>Southeast Shandong (4 807 kg·hm^-2)>Central Shandong (4 790 kg·hm^-2)>East Shandong (4 709 kg·hm^-2). At the municipal level, the straw resources were mainly distributed in Heze, Dezhou, Liaocheng, Jining and Weifang. The wheat and maize straw yields of these cities accounted for 57.5% and 55.5%, respectively. However, the proportions of wheat and maize straw outputs from Dongying, Zibo, Rizhao and Weihai were only 7.2% and 8.0%, respectively. In Shandong Province, the amounts of nutrient from wheat straw were 0.1394 million tons of N, 0.0513 million tons of P₂O₅, and 0.5090 million tons of K₂O. For maize straw, the outputs of nutrient were 0.1665 million tons of N, 0.0658 million tons of P₂O₅, and 0.3660 million tons of K₂O. In the regional scale, the substituting potentials of N, P₂O₅ and K₂O through wheat straw return were 16.7-18.7, 7.8-8.7 and 110.4-123.8 kg·hm^-2, respectively. The maize straw incorporation could substitute chemical fertilizers of N 25.4-27.6, P₂O₅ 11.8-12.8 and K₂O 83.2-90.5 kg·hm^-2 theoretically.

In summary, there were some differences in total straw yield and collectable straw per unit area among different wheat-maize rotation areas of Shandong Province. Therefore, these appropriate policies should be formulated based on local conditions to promote efficient utilization of wheat and maize straw resources. The fertilizer replacement potential of returned straw should be considered for nutrient management in wheat-maize rotation system, which was conducive to chemical fertilizer reduction and green agricultural development.