Wheat stubble effects

Wheat stubble may physically intercept up to half of the atrazine as it is applied (Ghadiri et al., 1984). Subsequent rains wash atrazine off the stubble and bring it into contact with the soil. In Nebraska, suppression of summer annual weeds in wheat stubble was proportional to the amount of stubble. Crutchfield et al. (1985) showed that even though heavier wheat stubble intercepted more metolachlor applied in spring prior to ecofallow com planting and reduced the amount of herbicide actually reaching the soil, weed suppression by the heavier stubble more than offset the interception effect. 

Chepil (1957) states that the amount of vegetative material required to protect against wind erosion depends primarily on surface roughness, degree of cloddiness, size of field, and strength of the wind. Five hundred pounds per acre of air-dry wheat stubble may be adequate on slightly erodible soil, one ton on moderately susceptible soil, and at least 4 tons on very erodible dune material. The effectiveness per unit of added material decreases as the amount added increases. 

Inhibitive effects are especially influenced by amount of cover crop biomass and soil management. Weed dry matter was reduced when rye residues were greater than 3.7 Mg ha-1 (Crutchfield et al. 1985), and when wheat residues were greater than Mg ha-1 (De Almeida 1985). Fisk et al. (2001) reported that burr medic (Medicago polymorpha L.) and barrel medic (M. truncatula Gaertn.) reduced by 70% weed dry weights while weed density was not affected if were no-till seeded as winter-killed cover crops into winter wheat (Triticum aestivum L.) stubble. 

Tamak JC, Narwal SS, Singh L, Singh I (1994) Effect of aqueous extracts of rice stubbles and straw stubbles on the germination and seedling growth of wheat, oat, berseem, and lentil. Crop Res 8 180-186... 

Growth inhibition of plants where crop residues are undergoing decay has been observed. For example, McCalla and Army (1961) observed that where wheat straw was left on the soil surface in a stubble mulch system of farming the growth of corn was sometimes retarded. The effect was observed on the very young plants which never recovered during the entire season. 

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