Rotations crop rotation

Other nonstructural approaches to erosion control on agricultural land include contour plowing and crop or pasture rotation. Crop rotation is a practice where a sequence of crops are cultivated on the land over a series of seasons or years. Rotating crops improves soil structure and makes it more resistant to erosion, particularly when paired with conservation-tillage techniques. In addition, varying the crops grown can reduce reliance on herbicides and pesticides by, for example, changing the crop to one that creates field conditions that are less favorable to the weeds or pests of concern. 

Nonchemical or traditional practices, such as weed seed removal, optimal crop seeding rates, crop selection, enhanced crop competitiveness, crop rotation, and mechanical weed control are all important components of an effective weed management program (458,459). In the context of modern intensive chemical herbicide appHcation, nonchemical practices may even represent an innovative approach to weed management and should receive careful consideration. 

Crop Rotations and Diversification. For thousands of years farmers have known that planting their crops in a new location about every 2 years helped reduce Insect, disease, and weed problems. Indeed, crop rotations are effective in reducing many pest problems and are often highly cost effective (15, 16). Unfortunately for many crops, the trend has been toward abandonment of rotations and increased monocultures. Where rotations are not practiced, certain pests tend to multiply as the crops are cultured on the same land year after year (23). As a result, the density of pest populations increases to levels that necessitate heavy pesticide applications. 

A practice somewhat related to crop rotation is crop diversification or polyculture (36). This approach involves planting selected combinations of crops, like corn and beans. 

Most biological and cultural pest controls return greater profits than pesticides. For example, biological pest controls are reported to return from 30 to 300 per dollar invested in control (16). Various cultural controls like host plant resistance, crop rotations, and tillage, also return 30 to 300 per dollar Invested in pest control (16). 

West, T. O. and Post, W. M. (2002). Soil organic carbon sequestration rates by tillage and crop rotation. A global data analysis. Soil Sci. Soc. Am. J. 66,1930-1946. 

N. Z. Lupwayi, W. A. Rice, and G. W. Clayton, Soil microbial diversity and community structure under wheat as influenced by tillage and crop rotation. Soil Biol. Biochem. 30 1733 (1998). 

OPPTS 860.1560 Reasonable Grounds in Support of the Petition OPPTS 860.1650 Submittal of Analytical Reference Standards OPPTS 860.1850 Confined Accumulation in Rotational Crops OPPTS 860.1900 Field Accumulation in Rotational Crops. 

Pesticides used on crops grown on the test site in previous seasons may also have an impact on the outcome of a field residue trial. Carryover of prior pesticide applications could contaminate samples in a new trial, complicate the growth of the crop in a trial, or cause interference with procedures in the analytical laboratory. For this reason, an accurate history of what has transpired at the potential test site must be obtained before the trial is actually installed. The protocol should identify any chemicals of concern. If questions arise when the history is obtained, they should be reviewed with the Study Director prior to proceeding with the test site. In most annual crop trials, this will not be a significant issue owing to crop rotations in the normal production practices, because the use of short residual pesticides and different chemical classes is often required for each respective crop in the rotation. However, in many perennial crops (tree, vines, alfalfa, etc.) and monoculture row crops (cotton, sugarcane, etc.), the crop pesticide history will play a significant role in trial site selection. 

The limit of detection (LOD) and limit of quantitation (LOQ) were statistically determined in alfalfa and clover raw agricultural commodities (rotational crops). The method LOD and LOQ for the EMA-producing metabolite were 0.004 and 0.012 mg kg respectively, and the LOD and LOQ for the HEMA-producing metabolite were 0.004 and 0.014mgkg respectively, for the alfalfa and clover... 

Sulfentrazone is a broad-spectrum, pre-emergent herbicide that provides good control over broadleaf weeds, grasses and sedges in crops and turf. The metabolism of sulfentrazone in animals and plants is similar. The major plant metabolite of sulfentrazone is 3-hydroxymethyl sulfentrazone (HMS). The soybean tolerance of 0.05 mg kg includes residues of sulfentrazone plus its major metabolite, HMS. The rotational crop tolerance includes residues of sulfentrazone and its major metabolites, HMS and... 

A sound crop rotational system is of basic importance to the organic farmer. It reduces the risk of diseases and pests associated with monoculture, gives better control of weeds, spreads the labour requirements more evenly over the year, reduces the financial risk if one crop yields or sells badly and provides more interest for the farmer. For instance, take-all is a disease that cannot even be controlled chemically. Winter crops are more susceptible to take-all than spring sown crops and wheat is more susceptible than barley, so the safest position for winter wheat is immediately after a break crop. 

Olesen, J.E., Rasmussen, I.A. Askegaard, M. (2000) Crop rotations for grain production. Proceedings of the 13th International IFOAM Scientific Conference, Basel, Switzerland, p. 145. 

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