Effect Of Fertilizaiton Patterns On Farmland Weed Seed Bank

Farmland weed is an important part in agricultural ecology system, and investigating the responses and mechanisms of farmland weed communities to fertilization patterns is the key for controlling farmland weed and protecting farmland weed diversity through nutrient management. There is no unified conclusion about the change rule of the features and mechanism of underground farmland soil weed seed bank that caused by fertilization patterns. Therefore, how to fertilize scientifically, which not only maintain the high soil fertility to meet the demand of crop’s high quality and yield, but also maintain the balance of farmland ecological system through the weed seed bank management to control weed reasonably. It has become the urgent problem which needs to be solved for the sustainable agricultural development.We surveyed the weed soil seed bank in a soybean-wheat rotation system at a long-term fertilization experiment at the Experimental Station of Ecological Environment under the Ministry of Agriculture in Mengcheng country of Anhui province. The author studied the farmland soil weed seed bank under five treatments of application chemical fertilizers and seven treatments of combined application of organic manure and chemical fertilizers in a wheat-soybean rotation system by using the method of community ecology and plant nutrition. The author analyzed its density, species composition and biodiversity in relation to fertilization patterns and the rate of community succession. Further more, to reveal the effect mechanism of fertilization pattern to soil weed seed bank, the author also analyzed the weed soil seed bank in different soil layers under long-term application of chemical fertilizers treatments, and investigated the relationship between the weed soil seed bank and soil depth. The main results are as follows:1. The application of chemical fertilization patterns significantly affected the density, species composition, biodiversity features and the rate of community succession of weeds.1.1The weed seeds of application of chemical fertilizers treatments affiliated with eighteen species and eleven families, and the weed soil seed densities were ranged from37,933to122,293grain/m2and the dominant species differed remarkably from one treatment to another.1.2The densities of soil weed seed bank decreased significantly (P<0.01) in a sequence of fertilizing pattern as NPK>NP>NK>CK>PK.1.3The diversity of the weed seed bank species in the soil decreased as the following orders:CK>NPK>PK=NK>NP for the species number, NP>CK>NK>PK>NPK for the Pielou index, CK>NP>NK>PK>NPK for Shannon-Wiener index and NPK>PK=NK>CK>NP for the Simpson index.1.4The increased sequence for the Whittaker index as CK<NPK<PK=NK<NP demonstrated a speeding-up rate of community succession. It implied that the long-term balanced fertilization (NPK) balanced fertilization had less effect on soil weed seed bank than the PK, NP or NK but yielded a more stable seed bank structure.1.5The variation in soil weed seed bank species may be caused by changes in climate, sampling time, herbicide use, cropping seasons and years.The results suggested that balanced fertilization is very beneficial to producing high yield and quality of agricultural products and stabilizing the soil weed seed bank, and is also an important measure to create reasonable, efficient and stable agro-ecosystem for better economic performance and ecosystem benefits.2. The combined application of organic manure and chemical fertilizers fertilization patterns significantly affected the density, species composition, biodiversity features of the weed seed bank.2.1The weed seeds of combined application of organic manure and chemical fertilizers treatments affiliated with sixteen species and ten families are detected, and the weed soil seed densities were ranged from15,995to106,300grain/m2.2.2In the treatments with combined organic manure and chemical fertilizers, the composition of weed species is relatively simple, and the number of the dominated species was from1to2. In the treatment with combined wheat straw and chemical fertilizers, the dominated species was Mollugo pentaphylla, and in the treatment with combined manure and chemical fertilizers, the dominated species was Ammannia baccifera. The densities of weed soil seed bank were reduced in the range from15,995to41,900grain/m2. The species richness was reduced in the range from7.67to9.33, and the Shannon-Wiener index and Pielou index were in the range of those of the CK2and NPK treatments (from1.5to2.0and from0.6to0.8).2.3Types and application amounts of applying organic fertilizers affected the weed species structure features significantly, and the influences of organic fertilizer types were greater than those of application amounts of wheat straw.The results of this paper showed that treatments of combined application of organic manure and chemical fertilizers not only benefited for obtaining higf crop yield, but also regulateed weed soil seed bank by adjusting the types and application amount of organic fertilizer to achieve economic and ecological benefits.3. The application of chemical fertilizers patterns might cause the reduction of weed species and biodiversity. Fertilization patterns had significantly affected the vertical distribution mode of dominant weed species, especially which grew in soybean cultivating season. Under different soil layers, fertilization patterns had little effect on the number of species and Pielou index; PK and NK fertilization patterns had significantly affected Shannon-Wiener index; the change of Simpson index was complicated and uncertain which require further studies. The change ranges of species composition, density and biodiversity features from top-layer to deep-layer decreased. It indicated that the influence of long-term different fertilization patterns decreased with the increasing of soil depth.