[Effects of short-term granulated straw incorporation on grain yield and soil respiration in a winter wheat-summer maize cropping system.]

Direct straw return to soils often leads to poor combination between soil and straw, decreases straw decomposition and suppresses crop growth. Those problems hamper crop yield and its stability. Granulated straw with high bulk density and small volume improves the straw quality and the soil-straw combination. It remains unknown how does the practice influence soil carbon emission and grain yield. A micro-field experiment was carried out to investigate the responses of wheat and maize yields, soil respiration and soil carbon use efficiency. There are three treatments: No straw incorporation (CK), conventionally chopped straw incorporation (CCSI), and granulated straw incorporation (GSI). The results showed that the GSI treatment increased grain yield. Compared with the CK and CCSI treatments, the total yield of wheat and maize was significantly increased by 14.0% and 5.8%, respectively. Meanwhile, the GSI treatment promoted soil carbon emission. The average rate of soil respiration and the cumulative carbon emission during growing season were significantly higher than that in the CK treatment. Compared with the CCSI treatment, the rate and the cumulative amount of soil carbon emission during the wheat growing season were significantly elevated by 15.2% and 8.9%, but there was no significant difference during the maize growing season. The GSI treatment decreased the sensitivity of soil respiration to temperature and increased soil carbon use efficiency. Compared with the CK and CCSI treatments, the sensitivity of the GSI treatment was significantly decreased by 22.6% and 10.1%, and the efficiency was increased by 2.3% and 1.9%. Although granulated straw incorporation promoted soil carbon emissions, it had higher soil carbon use efficiency than conventionally chopped straw incorporation due to the higher yield. The application of granulated straw incorporation could serve as a new option of straw return to soil in Huang-Huai-Hai region. Further research was needed to understand the long-term effects of granulated straw incorporation on soil carbon emission.

[Effect of Organic Manure Substitution of Synthetic Nitrogen on Crop Yield and N2O Emission in the Winter Wheat-Summer Maize Rotation System]

Controlling agricultural greenhouse gas emissions, such as N₂O, is important in mitigating global climate warming. Through monitoring the dynamics of N₂O emission fluxes, we investigated the effect of organic nitrogen (N) substitution of synthetic N on N₂O emissions and the yield of winter wheat and summer maize in the Guanzhong Plain of Shaanxi Province, China. The study involved six treatments, consisting of no fertilizer (CK), synthetic N, phosphorus (P), and potassium (K) fertilizers alone (NPK), 75% NPK+25% organic N through manure (25%M), 50% NPK+50% organic N (50%M), 25% NPK+75% organic N (75%M), 100% organic N (100%M). The results showed that the peak value of the N₂O emission flux appeared after fertilization, rainfall, and irrigation. In the wheat season, the emission flux of N₂O varied from -1.33 to 144.2 μg·(m²·h)^-1, with the highest peak value in the NPK treatment. In the maize season, the emission flux of N₂O varied from 88.2 to 1800.1 μg·(m²·h)^-1, and the 50%M treatment showed the highest peak value. The range in the total amount of N₂O emissions from the different treatments in the wheat-maize rotation system was 429.8-2632.1 g·hm^-2, and the amount for the treatments decreased in order as follows:50%M > 25%M > NPK > 75%M > 100%M > CK. The yields of wheat, maize, or wheat plus maize were significantly higher in the fertilized treatments compared to the CK. Organic substitution treatments significantly increased wheat yield by 26.1% to 50.0% relative to the NPK treatment. While the maize yield in 50%M and 75%M treatments was similar to that in the NPK treatment, the 25%M and 100%M treatments showed significantly lower yields than with the NPK treatment. The total yield of wheat plus maize varied from 9166 to 17496 kg·hm^-2, of which total yield was significantly higher with 50%M and 75%M compared to NPK. Overall, the 75%M treatment is the best measure to guarantee crop yield and to reduce N₂O emissions in the wheat-maize rotation system based on a one year study in the Guanzhong plain of Shaanxi Province.