Differential response of weed species to added nitrogen

Abstract

Information on responses of weeds to various soil fertility levels is required to develop fertilizer management strategies as components of integrated weed management programs. A controlled environment study was conducted to determine shoot and root growth response of 23 agricultural weeds to N fertilizer applied at 0, 40, 80, 120, 180, or 240 mg kg−1 soil. Wheat and canola were included as control species. Shoot and root growth of all weeds increased with added N, but the magnitude of the response varied greatly among weed species. Many weeds exhibited similar or greater responses in shoot and root biomass to increasing amounts of soil N, compared with wheat or canola. With increasing amounts of N, 15 weed species showed a greater increase in shoot biomass, and 8 species showed a greater increase in root biomass, compared with wheat. Ten weed species exhibited increases in shoot biomass similar to that exhibited by canola, and five weed species showed greater increases in root biomass than did canola, as N dose was increased. All crop and weed species extracted > 80% of available N at low soil N levels. At the highest N dose, 17 of 23 weed species took up similar or greater amounts of soil N than did wheat, and 6 weed species took up N in amounts similar to that taken up by canola. These findings have significant implications as to how soil fertility affects crop–weed competition. The high responsiveness of many weed species to N may be a weakness to be exploited through development of fertilizer management methods that enhance crop competitiveness with weeds.

The biology of Canadian weeds. 138. Kochia scoparia (L.) Schrad.

“…In greenhouse studies (Blackshaw et al 2003), kochia shoot and root biomass response was similar to or greater than canola, respectively, to increasing amounts of N; the species was among the most responsive weeds to N (Lugg et al 1983). Kochia root plus shoot N uptake comprised about 90% of soil available N (Blackshaw et al 2003).…”

“…In greenhouse studies (Blackshaw et al 2003), kochia shoot and root biomass response was similar to or greater than canola, respectively, to increasing amounts of N; the species was among the most responsive weeds to N (Lugg et al 1983). Kochia root plus shoot N uptake comprised about 90% of soil available N (Blackshaw et al 2003). In similar greenhouse studies investigating response to P fertilizer, kochia shoot and root biomass responded less than wheat or canola to added fertilizer P (5Á60 ppm); however, shoot biomass did increase by two-to threefold in response to fertilization relative to the unfertilized control (Blackshaw et al 2004).…”

The Biology of Canadian Weeds. 137. Brassica napus L. and B. rapa L.

“…In an interference study between domesticated B. rapa and tartary buckwheat (Fagopyrum tataricum L.) where B. rapa was grown as the crop, O'Donovan (1994) found that B. rapa reproductive output was least affected at high B. rapa densities (200 plants m (2 ) compared with lower densities (50 and 100 plants m (2 ). Blackshaw et al (2003) compared shoot and root growth of 23 agricultural weeds and the crop B. napus to a range of N fertilizer rates from 0 to 240 mg kg (1 soil in a controlled environment study. Shoot biomass production of B. napus and of 10 other species [e.g.…”

Effect of N and P Fertilization on Weed Flora of Maize (Zea Mays L.) Crop

“…The specific weed is a nitrophilous plant and, therefore, responds to nitrogen fertilization very well (Nelson, 2015). Finally, Nutrisphere 100% treatment resulted in the higher total biomass, a finding rather anticipated, as it is generally known that biomass of all weed species tend to increase under nitrogen fertilization (Blackshaw et al, 2003).…”