长期不同施肥方式对麦田杂草群落的影响

以太湖地区农业科学研究所31a的长期肥料定位试验田为材料,分别于2011—2012年小麦苗期、拔节期和收获期进行了杂草群落调查,研究杂草类型与密度的分布、杂草多样性指数的变化,并对杂草种群分布与土壤养分因子进行冗余分析。结果表明:小飞蓬、看麦娘、大巢菜、稻槎菜、通泉草是本地区小麦生长期的主要杂草类型;随着小麦的生长以及氮肥、有机肥的施入,杂草密度呈下降趋势;施入有机肥降低了麦季杂草的群落多样性指数,在小麦生长的不同时期均衡施肥的CNPK处理以及不施肥的C0处理的群落各项多样性指数能维持在一个较高的水平。RDA分析显示土壤氮含量以及有机质含量与第一排序轴相关性大,是对杂草分布影响最大的两个土壤养分因子。太湖地区稻麦两熟制条件下,长期有机无机肥料单一或配合投入可显著影响麦田杂草的群落组成,其中氮肥和有机肥的施入能显著降低杂草密度;土壤养分的差异影响田面杂草密度和优势种群,均衡施肥能降低优势杂草种群的优势地位,抑制其发生危害程度,提高农田生态系统的生产力及稳定性。

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

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.