Cover Crops Affect Sorghum Seedling Growth

Abstract

Recently killed cover crops often interfere with crop seedling growth. Controlled‐environment and field studies were conducted to characterize the nature and persistence of cover crop interference with sorghum [Sorghum bicolor (L.) Moench] seedling growth and to test several seed‐zone management practices that might alleviate detrimental effects. Germination, root and shoot length, and disease incidence of sorghum germinated at 25°C for 5 d in soil collected 2, 4, 7, 14, 23, and 32 d after killing cover crops indicated legume cover crops were more detrimental to seedling growth than were nonlegumes. Surface residues, subsurface residues, and residue leachates contributed to the deleterious effects. Seedling shoot disease incidence of 50% persisted through 32 d when legume residues were mixed into soil or placed on top of soil at planting, but disappeared by 7 to 14 d if residues were removed. Pathogenic organisms isolated from lesions on seedlings indicated legume cover crops increased damage due to Rhizoctonia solani Kühn. In a no‐till field study, stand density was reduced 15% and aboveground seedling dry weight was reduced 45%, from 85 to 45 mg plant−1 28 d after planting, when sorghum was planted 1 d after killing crimson clover (Trifolium incarnatum L.) compared with planting 21 d or longer after killing. Insecticide, activated charcoal, or CaO2 seed coating improved sorghum stand density 15%, but did not affect seedling size. In‐furrow fungicide drench had no effect on stand density, but phytotoxic effects of the fungicide reduced shoot and root growth rates in both field and controlled‐environment studies. Residue removal combined with selected in‐furrow treatments may allow the interval between cover‐crop killing and successful no‐till planting to be reduced to less than 7 d.

Importance of cover crops in alleviating negative effects of reduced soil tillage and promoting soil fertility in a winter wheat cropping system

“…Too high biomass could have prevented the good emergence of wheat at seeding, or biomass decomposition in spring could have induced nitrogen immobilisation, due to high C/N ratio, linked to the lower proportion of legumes observed this year. These are two negative aspects of cover crop cultivation often mentioned in this context (Dabney et al, 1996;Fageria et al, 2005). Producing the highest possible cover crop biomass is thus not necessarily the objective in such systems.…”

Time Interval Between Cover Crop Termination and Planting Influences Corn Seedling Disease, Plant Growth, and Yield

“…Similarly, Sharma-Poudyal et al (2016) found that increasing the time interval between herbicide application to a wheat cover crop and onion planting reduced the infection of onion roots by Rhizoctonia spp. Finally, Dabney et al (1996) reported that sorghum root disease incidence decreased when the time interval between spraying legume cover crops and planting sorghum was increased. These studies suggest that the time interval between termination of rye cover crops and corn planting may also be important.…”

Cropping system effects on giant foxtail demography

“…. Soil phytotoxicity during giant foxtail and com seedling recruitment was assessed with bioassays measuring effects of field soil on germination percentage and radicle growth (Dabney et al 1996).…”

“…Soil phytotoxicity during giant foxtail and corn seedling recruitment was assessed with bioassays (Dabney et al 1996). Forty giant foxtail seeds or 10 corn seeds were spaced in a line 10 cm from the top edge of two 25 cm by 38 cm sheets of germination paper moistened with 20 mL distilled deionized HiO.…”

“…Soil organic amendments can alter the biological (Craft and Nelson 1996; Dabney et al 1996), physical (Drury et al 1999;Jacobowitz and Steenhuis 1984) and chemical (Tiquia and Tam 1998;Conklin et al 2002) properties of soil in different ways, depending upon what types of amendments are used and how they are handled. Because there are many ways in which soil organic amendments can be managed, it is important to know if some choices are more effective for weed prevention than others.…”