Medics and clovers in wheat-no-tillage corn rotations with insights into their use by farmers.

摘要

Forage legumes can be beneficial as cover crops in grain crop rotations typical of the north central USA. This research was conducted to investigate the potential of Medicago (annual medics) species and clovers as cover crops for no-tillage corn (Zea mays L.). Specific objectives were (1) determine legume biomass, tissues nitrogen (N) concentration, biomass N, and dinitrogen fixation ability when frost-seeded into winter wheat or planted after wheat harvest, (2) measure the effect of cover crops in the rotation in terms of plant available soil N, corn grain yield and biomass, fertilizer replacement value, and uptake of annual legume {dollar}sp{lcub}15{rcub}{dollar}N, (3) determine the effect of fall seeded legumes on weed suppression, (4) investigate whether participatory approaches to the generation and dissemination of information and technologies around sustainable agriculture, specifically cover crops, may be more appropriate than conventional methods.; Annual legume cover crops established after wheat harvest demonstrated excellent potential for N{dollar}sb2{dollar} fixation (15.7 to 64.9% of biomass N) and biomass N accumulation (48 to 206 kg N ha{dollar}sp{lcub}-1{rcub}{dollar}) and were comparable to fall and frost-seeded red clover (Trifolium pratense L). Soil inorganic N levels were often higher following legumes than the no cover control. Fertilizer replacement values were between 24 and 112 kg N ha{dollar}sp{lcub}-1{rcub}{dollar} for legumes, whereas, actual legume {dollar}sp{lcub}15{rcub}{dollar}N recovery in a following crop was between 9 and 16% indicating rotation effects beyond N contribution.; Density and dry weight of winter annual weeds as well as dry weight of perennial weeds following, fall-planted cover crops, were almost always lower than when following the no cover crop control. The effect of cover crops on the density of summer annual and perennial weeds was not as pronounced as for spring annuals. Summer weed density and dry weight were significantly lower where cover crop residue was retained compared to when it was removed.; Evidence that participatory approaches would be effective in facilitating the generation and dissemination of sustainable agriculture technologies was found, including: a desire by farmers for more farmer-to-farmer interaction indicating an attraction to the participatory learning process, a desire by knowledge brokers for greater skills in facilitating participatory methods, and that a limited number of farmers are currently learning to integrate their farms with participatory approaches.