Stubble-mulch farming

Zingg, A.W. and C.J. Whitfield (1957). A summary of research experience with stubble-mulch farming in the western states. Washington, DC USDA, Agric. Tech. Bull., 1166, 56 pp. 

The scientific basis for most of these benefits resulting from reduced tillage that are not obvious have been discussed in this chapter. The phases of the subject that relate more specifically to stubble-mulch farming are considered in the chapter that follows. 

Stubble-mulch farming is commonly defined (McCalla and Army, 1961 Horning and Oveson, 1962) as a year-round way of managing plant residues on cropland in which harvesting, cultivating, seedbed preparation, and planting are performed in such a way as to leave the residues of the previous crop on top of or near the soil surface. 

A soil that is cropped and heavily mulched with straw or other suitable plant material is protected from erosion in much the same manner as are forest soils. There is no raindrop splash and little if any runoff. Such soils are nearly always well aggregated and capable of rapidly absorbing any water that reaches them. Where the mulch is thin, as in stubble-mulch farming, there is less protection of the soil but the water is held back long enough for most of it to infiltrate into the soil. 

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. 

Residues left on the soil surface decompose at a slower rate than when they are buried, and under some conditions considerable residue may remain from one season to the next (Brown and Dickey, 1970). This is of course very desirable in a stubble-mulch stem of farming. Such resistance to decay is dependent upon the kind of residue, temperature, moisture relations, and extent of soil disturbance during the tillage operations. 

Various types of machinery are used in the stubble-mulch system of farming, depending on the crop grown, soil, climate, amount and type of residue, and local conditions. Carter and McDole (1942), Duley and Russel (1948), Jacks et al. (1955) Horning and Oveson (1962), and many others have described the leading types of equipment used. Of course not all of this equipment is suitable for use in any one farming operation. 

Comparisons of stubble mulch with complete chemical fallow systems of farming have usually given results that favor the former system. For example. Black and Power (1965) reported that wheat yields on stubble-mulched soils were higher than where spray was used. Furthermore, neither chemical fallow nor combinations of chemical and mechanically-tilled plots resulted in more moisture conservation than with conventional stubble mulch. Wind erodibility was, however, less with complete chemical fallow soils, doubtless because of complete absence of tillage. 

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