Abstract
In the North Central USA, intersowing cover crops into standing maize (Zea mays L.) is required to establish plants large enough to afford the benefits of a cover since there is limited favorable weather for cover crop growth after maize harvest. The objective of this study was to quantify the impacts of the planting method and time of planting of three cover crop species when grown with or without maize competition on their establishment. Experiments were conducted in three environments during 2018 and 2019. Experiments consisted of a factorial combination of timing of cover crop planting (V7 and R4 growth stage of maize), cover crop species (camelina (Camelina sativa (L.) Crantz), rye (Secale cereale L.), or radish (Raphanus sativus L.), method of sowing (drilled or broadcast), and maize removal. Initial cover crop populations were similar regardless of maize removal or stage of maize when sown, but intersown cover crops produced only 3% of the fall biomass, compared with treatments with maize-removed when sown at the V7 stage of maize and 14% when sown at the R4 stage. Limited light intensity (less than 20%) under the maize canopy was the main factor affecting interseeded cover crop development. Radish was more sensitive to shading than the other cover crops. Camelina and rye sown at the R4 stage of corn produced similar spring biomass as earlier-sown cover crops. Intersown cover crops had no negative effect on maize grain yield.
Highlights
Cover crops have the potential of protecting the soil from erosion, increasing soil organic matter, improving soil aggregate stability and soil water retention, scavenging and releasing nutrients, and stimulating microbial growth and diversity [1,2,3,4,5,6]
Rye and radish established at higher densities when drilled compared with broadcasting at the V7 maize growth stage (Table 2)
The reduced plant density for the early planting could be attributed to a dry period during cover crop emergence in Hickson in 2018 and excessive rainfall in 2019, for both locations (Figure 1)
Summary
Cover crops have the potential of protecting the soil from erosion, increasing soil organic matter, improving soil aggregate stability and soil water retention, scavenging and releasing nutrients, and stimulating microbial growth and diversity [1,2,3,4,5,6]. In the upper Midwest of the USA, spring weather conditions prior to primary crop establishment promotes the greatest risk of nitrogen (N) loss in annual cropping systems [7]. According to Randall et al [8], 69% of the annual N loss occurs as runoff in April through June in maize (Zea mays L.)–soybean (Glycine max (L.) Merr.) rotations in the upper Midwest. Winter annual cover crops can be incorporated into maize–soybean rotation to stabilize N in plant biomass and reduce its loss [9,10,11]. To have a reasonable impact on N uptake, cover crops need to be well established to have adequate fall and spring growth prior to termination [12,13]
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