Effect of long-term fertilization pattern on weed community diversity in wheat field

Abstract

Weeds are an essential biological component of farmland ecosystems. The maintenance of an appropriate amount of weeds plays a role in protecting the biological diversity of farmlands. Weeds affect crop yields by means of competition with crops for water, nutrients, light, and other natural resources and can also effectively change the farmland ecosystem structure and promote the cycling and energy flow of mineral elements and organic materials in the soil. The goal of weed management is to reduce the impact of weed growth on the crop yield and to inhibit hard-to-control weeds from becoming dominant, while simultaneously maintaining the diversity of the weed community which is controllable. At present, the comprehensive control of weeds through improving competitiveness of the crops has received growing attention; generally speaking, fertilizers and herbicides are the primary input for the farmland ecosystem. Fertilization can alter the natural succession process of the weed community in farmland by directly improving the yield and competitiveness of crops and changing the nutrient composition and the structure of soil. We studied the heterogeneity of the weed community diversity in wheat field in a rice-wheat rotation system after a 31-year long-term application of different organic or non-organic fertilizers, analyzed the effects of major nutrients on the characteristics of the weed, provided information on nutrient management for the coordination of weed control in wheat field, which contribute to the the protection of biodiversity and decrease of noxious weeds. Chemical fertilizer treatments were selected as follows: C0 (no fertilizer), CN (N fertilizer), CNP (N plus P fertilizer), CNK (N plus P fertilizer), CPK (P plus K fertilizer) and CNPK (N plus P and K fertilizers); manure treatments were selected as follows: M0 (manure), MN (manure plus N fertilizer), MNP (manure plus N and P fertilizer), MNK (manure plus N and K fertilizer), MPK(manure plus P and K fertilizer), MNPK(manure plus N, P and K fertilizer). We analyzed the Simpson, Shannon, Margalef, and Pielou indexes of these samples, at the same time, redundancy analysis (RDA) was executed to mining the relationship between fertilizer management and weeds. Among the weeds, Conyza canadensis, Vicia sativa, Alopecurus aequalis, Mazus japonicus and Lapsana apogonoides showed high density and were widely distributed in every trial area. These plants belong to the main dominant weed community that affects wheat yield in the Taihu area. The long-term application of nitrogen and organic fertilizers could significantly reduce the density of weeds; non-organic fertilizers and a combination of non-organic and organic fertilizers had a significant influence on the diversity of weeds, the application of organic fertilizers could reduce the diversity indices of weed community. In terms of the soil nutrient system itself, the soil organic materials and nitrogen content are the main environmental factors that affect the distribution of weeds. The result also indicates that the application of a balanced fertilizer allows all weed species available to shrive. Moreover, the balanced fertizer affects the appearance of dominant weeds, and improve the productivity and stability of farmland ecosystems.