Impact of fertilizing pattern on the biodiversity of a weed community and wheat growth

Abstract

Weeding and fertilization are important farming practices. Integrated weed management should protect or improve the biodiversity of farmland weed communities for a better ecological environment with not only increased crop yield, but also reduced use of herbicides. This study hypothesized that appropriate fertilization would benefit both crop growth and the biodiversity of farmland weed communities. To study the effects of different fertilizing patterns on the biodiversity of a farmland weed community and their adaptive mechanisms, indices of species diversity and responses of weed species and wheat were investigated in a 17-year field trial with a winter wheat-soybean rotation. This long term field trial includes six fertilizing treatments with different N, P and K application rates. The results indicated that wheat and the four prevalent weed species (Galium aparine, Vicia sativa, Veronica persica and Geranium carolinianum) showed different responses to fertilizer treatment in terms of density, plant height, shoot biomass, and nutrient accumulations. Each individual weed population exhibited its own adaptive mechanisms, such as increased internode length for growth advantages and increased light interception. The PK treatment had higher density, shoot biomass, Shannon-Wiener and Pielou Indices of weed community than N plus P fertilizer treatments. The N1/2PK treatment showed the same weed species number as the PK treatment. It also showed higher Shannon-Wiener and Pielou Indices of the weed community, although it had a lower wheat yield than the NPK treatment. The negative effects of the N1/2PK treatment on wheat yield could be balanced by the simultaneous positive effects on weed communities, which are intermediate in terms of the effects on wheat and weeds.

Figure 1. The influence of fertilization on the density of the weed community.

Figure 2. The influence of fertilization on the biomass of the weed community.

Figure 3. The influence of fertilization on the species diversity of the weed community.

(a) Rank-abundance plots corresponding to different fertilization treatments in a winter wheat field. (b) The influence of fertilization on the biodiversity indices of weed communities (H′, Shannon-Winner Index; J, Pielou Index; and D, Simpson index). Species reference: (1) Avena fatua L., (2) Calystegia hederacea Wall., (3) Cirsium segetum Bge., (4) Cyperus rotundus L., (5) Erigeron annuus (L.) Pers., (6) Euphorbia helioscopia L., (7) Galium aparine L. var. tenerum (Gren.et Godr.) Rcbb., (8) Geranium carolinianum L., (9) Lithospermum arvense L., (10) Mazus pumilus (Burm. f) V. Steenis., (11) Plantago virginica L., (12) Veronica persica Poir., (13) Vicia sativa L.

Figure 4. The effects of fertilization on average weed densities.

Analyses of variance were performed on log_e-transformed data, but means of untransformed data are shown. Error bars are the SE of the mean.

Figure 5. The influence of fertilization on plant height of G. carolinianum (A), V. sativa (B), G. aparine (C) and V. persica (D).

Figure 6. The influence of fertilization on wheat plant height at three growing periods.

Figure 7. The influence of fertilization on wheat yield and light transmittance at the ground surface.