Cropping systems

O2 availability, water content. Structural - soil type, porosity, clay content, fertility. Agricultural - Fertilizer addition, herbicide pesticide application, tillage, cropping systems etc. 

A. D. Rovira, L. F. Elliott, and R. J. Cook, The impact of cropping systems on rhizosphere organisms affecting plant health. The Rhizosphere (J. M. Lynch, ed.), Wiley, Chichester, 1990, p, 389. 

P. A. Harris, H. H. Schomberg, P. A. Banks, and J. Giddens, Burning, tillage and herbicide effects on the soil microflora in a wheat-soybean double-crop system. Soil Biology and Biochemistry 27 153 (1995). 

P. de Willigen, Nitrogen turnover in the soil crop system—comparison of 14 simulation models. Feitil. Res. 27 141 (1991). 

R. F. Grant, The distribution of water and nitrogen in the. soil-crop system a simulation study with validation from a winter wheat field trial. Fertil. Res. 27 199 (1991). 

M. van Noordwijk, G. Brouwer, H. Koning, F. W. Meijboom, and W. Grzebisz, Production and decay of structural root material of winter wheat and sugar beet in conventional and integrated cropping systems, Agric. Ecosyst. Environ. 51 99... 

Major registrants typically conduct as many residue trials as possible on their own research farms and contract the remainder to independent contract research companies. These contract research companies range in size from those that have several research farms to husband and wife teams with only one site. They also may include independent researchers who do not own a permanent test site but contract small plot test areas from farmers inside commercial production acreage. The goal of these trials is to conduct the smdy in a cropping system environment that represents commercial production systems, thereby ensuring that the raw agriculture commodities harvested represent commercially available commodities. 

Koocheki, A., Nassir, M., Zare, A. Alimoradi, L. (2002) Weed Dynamics of Conventional and Ecological Cropping Systems in Different Rotations with Wheat. Proceedings of the 14th IFOAM Organic World Congress, Victoria BC, Canada, p. 59. 

Another approach is the utilization of allelopathic rotational crops or companion plants in annual or perennial cropping systems (19). Living rye (Secale cereale L.) and its residues have been shown to provide nearly complete suppression of a variety of agroecosystem weeds (33). Similarly, residues of sorghums, barley, wheat and oats can provide exceptional suppression of certain weed species Q ). Although some progress has been made on identifying the allelochmicals from these plants, much remains to be accomplished. 

Cultivation of soil has and will continue to be an important means of controlling weeds (1). However, extensive soil cultivation leads to various problems such as losses of soil, soil moisture and nutrients. This results in water pollution by both the soil itself and pesticides and nutrients associated with it (2, 3, 4). Minimum or no-till cropping systems can reduce these problems because various crop residues (i.e., mulch) are left on the soil surface with a minimum of soil disturbance in planting the crop. 

Even with these problems, attempts have been made to demonstrate that mulches suppress weeds allelopathically. Putnam and DeFrank (12) and Barnes and Putnam (39) used Populus wood shavings to separate chemical and physical effects of mulches. Their work indicated that certain mulches do possess allelopathic potential. Liebl and Worsham (9) and Shilling and Worsham (14) placed mulch on tilled soil, after tilling, in an attempt to provide the weeds with an exposure to light. Their work also indicated that at least part of the suppression of weeds by wheat and rye mulch is allelopathic. Thus, research to date indicates that both mulch and the lack of soil tillage contributes to the suppression of weeds in no-till cropping systems. 

Table I. The Effect of Tillage and Rye Residue (Above- and Belowground) on Weed Control Averaged Across Three Cropping Systems at Clayton, NC, in 1982 and 1983...

Chung, S., Gassman, P.W., Huggins, D.R., and Randall, G.W., EPIC tile flow and nitrate loss predictions for three Minnesota cropping systems, Journal of Environmental Quality, 30, 822-830, 2001. 

The saturated soils that occur during wetland, or lowland, rice cultivation give rise to a set of physical, chemical, and biological properties that are quite different from upland soils. Rice is the only major row crop produced under flooded-soil conditions and the absence of air-filled pores along with reduced soil-atmosphere interactions result in an almost entirely different set of processes than those occurring in upland cropping systems. 

Grant C.A., Peterson G.A., Campbell C.A. Nutrient Considerations for Diversified Cropping Systems in the Northern Great Plains. Agron J 2002 94 186-198. 

Drinkwater L E, Wagoner P and Sarrantonio M (1998). Legume-based cropping systems have reduced carbon and nitrogen losses . Nature, 396, 262-264. 

Organic crop husbandry - a model for sustainable crop systems... 

Piorr H P (1992), Phytopathological advantages and risks of organic farming systems Future perspectives to improve organic cropping systems , in Altman J, Pesticide-interactions in Crop Production Beneficial and deleterious effects, CRC Press, Cleveland, 461 172. 

Crop rotation is the keystone of organic cropping systems and its importance is emphasized by all organic crop production standards, not only for its role in crop protection, but also for its contribution to soil fertility. Soil fertility may influence the severity of disease infection or offset its effects by accelerating the build-up of yield before the disease takes its toll. This aspect is considered further in Section 18.4.4. 

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