Nitrogen management will influence threshold values of green foxtail (Setaria viridis) in corn

Abstract

Environmental legislation may impose limitations on the quantity of nitrogen (N) used in corn production on the basis of soil type and ground water flow. If N rates are reduced, this might influence the relative competitiveness of weed species. Therefore, the objectives of this research were to develop a surface response model to provide estimations of the effect of differing N rates on threshold values of green foxtail in corn and to use this model as a theoretical framework for hypothesis testing. Field experiments were conducted from 1999 to 2001 to examine the interaction of N rate and green foxtail density on corn grain yield. The experiment was designed as a two-factor factorial with N levels ranging from 0 to 200 kg N ha−1and targeted green foxtail densities ranging from 0 to 300 green foxtail plants m−2. The addition of up to 200 kg N ha−1increased corn grain yield in both weed-free and weedy treatments. Corn yield loss attributed to green foxtail ranged from 35 to 40% at 0 kg N ha−1to 12 to 17% at 200 kg N ha−1. Ridge analysis of the response surfaces indicated that optimal corn grain yield could be achieved at derived values of 131 to 138 kg N ha−1while maintaining a green foxtail density of 8 to 9 green foxtail plants m−2on a sandy soil with less than 2% organic matter. The analyses of simulation results led to the generation of hypotheses of practical relevance to N management. On the basis of the generated hypotheses, a legislated reduction in N or an increase in the cost of N fertilizer would result in a lower threshold value for green foxtail in corn. If legislation were to ban the use of all herbicides in corn production, higher N rates or an increase in mechanical weed control measures would be required to offset yield losses caused by green foxtail. The human health and environmental consequences of such legislation would be significant.

Corn and Palmer amaranth (Amaranthus palmeri) Interactions with Nitrogen in Dryland and Irrigated Environments

“…Corn grain yield in the absence of green foxtail [Setaria viridis (L.) Beauv. ] increased with the addition of N (Cathcart and Swanton 2003), but in the presence of variable densities of green foxtail that emerged with the crop, corn grain yield decreased by an Table 2. average of 18 to 23% despite increasing rates of N. In the presence of green foxtail, corn yield reductions were 35 to 40% with 0 kg N ha 21 , were only 20 and 8% at 100 kg N ha 21 , and were 12 to 17% at 200 kg N ha 21 , for 1999-2001, respectively (Cathcart and Swanton 2003. These losses indicated that green foxtail was not as responsive to available N as corn and amount of yield loss decreased as N rate increased.…”

Effect of previous crop and herbicides on weed growth and wheat yield

“…Higher available N after lentil than wheat has also been generally reported (Grant et al 2002). Several weeds are heavy users of available N (Moyer and Dryden 1977;Moyer et al 1979;Blackshaw et al 2003;Cathcart and Swanton 2003); therefore, similar available N after all crops with no herbicides can be attributed to nitrogen use by weeds. Total crop plus weed biomass (data not presented) was not affected by herbicide (P > 0.05), suggesting that a similar amount of N was required to produce weed and crop biomass.…”

Competition Between Wheat and Ryegrass Under Different Levels of Nitrogen Fertilization

“…Fertilization management is one of these practices; it can change the interference between culture and competitor (Liebman and Janke, 1990;Ditomaso, 1995). Studies reported that N increased the competitive capacity of weeds over cultures (Santos et al, 1998;Dhima and Eleftherohorinos, 2001;Andreasen et al, 2006) or that it benefited cultures in the presence of weeds (Mishra and Kurchania, 2001;Evans et al, 2003;Cathcart and Swanton, 2004;Abouziema et al, 2007).…”