Abstract:

To clarify the effects of different exogenous organic matter additions on soil enzyme activities, bacterial diversity, and crop yield in the sandy soil area of the Yellow River old course, this study conducted a field experiment based on the full straw return mode with no application of exogenous organic matter as the control (CK), and three treatments were set up: additional application of nitrogen fertilizer and biological agents (NM), additional application of organic fertilizer (F), and additional application of organic fertilizer and soil enzyme additives (FE). Indicators such as soil physical and chemical properties, enzyme activities, microbial diversity and wheat yield components after adding different exogenous organic matters were analyzed. The results showed that: application of organic fertilizer and soil enzyme additive (FE treatment) significantly increased soil pH by 2.28% compared to CK, but had no significant effect on soil organic matter and total nitrogen. The addition of different exogenous organic materials significantly promoted the activities of soil enzymes α-glucosidase (AG), β-glucosidase (BG), N-acetyl-glucosaminidase (NAG), leucine aminopeptidase (LAP) and β-xylosidase (XYL), with the FE treatment showing the best performance. Compared to CK, the enzyme activities in the FE treatment increased by 83.09%, 75.47%, 186.43%, 112.01% and 67.83%, respectively. There were significant differences in microbial composition between different treatments. The addition of organic fertilizer and soil enzyme additive significantly affected the bacterial richness indices Chao1, ACE, and Shannon, which increased by 3.43%, 1.95% and 2.26% respectively, compared to CK. The nitrogen fertilizer and bio-inoculant treatment (NM) increased the relative abundance of Bacillus and Flavobacterium in the soil bacteria, while the organic fertilizer treatment (F) significantly increased the relative abundance of Kouleothrix. The addition of nitrogen fertilizer and bio-inoculant effectively promoted the increase of wheat single-spike grain weight and grains per spike. The addition of organic fertilizer and soil enzyme additive significantly increased the number of wheat spikes number, thousand-grain weight, and yield. The spike number, thousand-grain weight and yield of FE treatment were 7.50 %, 9.67 % and 11.46 % higher than those of CK, respectively. The NM treatment had 9.72% higher single-spike grain weight and 6.09% more grains per spike compared to CK. In summary, the application of organic fertilizer and soil enzyme additive can promote soil pH, increase soil enzyme activity, improve soil bacterial diversity and community richness, and increase wheat yield, providing a theoretical basis for rational fertilization and high and stable yield of crops in the Yellow River floodplain agricultural system.

Key words: exogenous organic matter, wheat, soil, bacterial diversity, the old Yellow River course region