Objectives We investigated the characteristics of weed community under long-term different fertilization treatments in a maize-winter wheat rotation system, aiming to provide a scientific basis for weed control in the rain-fed agriculture region of Hilly Loess Plateau in eastern Gansu Province, China.

Methods  A long-term fertilization experiment, initiated in 1978 in Jingchuan County, Gansu Province, was conducted under a is summer maize-winter wheat rotation system. Six treatments were included: no fertilization (CK), nitrogen fertilizer (N), nitrogen and phosphorous fertilizer (NP), straw returning combine with NP fertilizer (SNP), manure (M), and manure combine with NP fertilizer (MNP). In 2021, after the wheat harvest, weed density, biomass and community diversity were investigated, and soil samples were collected to analyze physical and chemical properties. Redundancy analysis (RDA) was use to explore the relationship between weed diversity and soil nutrient factors.

Results Compared with CK, all the fertilization treatments significantly increased soil nutrient contents, with the MNP treatment showing the highest increase: organic matter, total N, total P and alkali-hydrolyzed N significantly increased by 70.32%, 67.18%, 92.09% and 79.46%, respectively. A total of 21 weed species, belonging to 11 families, were recorded in the fields. Predominant weeds species included Setaria viridis from Poaceae family, Artemisia selengensis Turcz from Asteraceae family, Acalypha australis from Euphorbiaceae family, and Chenopodium album from Amaranthaceae family. Weed density among the treatments was in order of CK>NP>N>SNP>M>MNP. The M treatment was recorded the highest total weed biomass (78.79 g/m²), which was 78.99%, 31.97%, 121.40%, 129.92% and 73.69% higher than that of CK, N, NP, SNP and MNP treatments, respectively. Weed diversity index (1.36) and evenness index (0.59) in M treatment were also the highest, while the highest dominance index (0.82) was in SNP treatment, and the highest species richness index (4.21) was in MNP treatment. Soil nutrients influenced weed density to varying degrees. Total nitrogen had the greatest effect, with an interpretation rate of 38.70% (F=12.5, P<0.01), followed by total phosphorus and available potassium, with interpretation rates of 32.2% and 21.3% respectively (F=9.5 and 5.4, P<0.01). The effects of available phosphorus and pH on weed density were relatively small, with interpretation rates of 6.6% and 1.3% respectively (F=4.9 and 0.08, P>0.05).

Conclusions In the maize-winter wheat rotation system of the Loess Plateau of Longdong, soil nitrogen, phosphorous and potassium contents significantly influence weed species composition and density. Application of chemical N or NP fertilizers leads to increased weed species richness and density, while manure application promotes greater weed biomass. Long-term combined application of organic and inorganic fertilizers is conducive to improving soil fertility, reducing weed community density, stabilizing species diversity, and promoting sustainable agricultural production.