Alfalfa crop rotation

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. 

To protect against pests, organic farmers alternate the crops planted on a particular plot of land. Such crop rotation works fairly well because different crops are damaged by different pests. A pest that thrives on one seasons crop of corn, for example, will do poorly on the next season s crop of alfalfa. For fertilizer, organic farmers rely on compost, shown in Figure 15.29. They also include nitrogen-fixing plants in their crop-rotation schedules. 

A publication from the Land Stewardship Project describes four sustainable farms in Minnesota (Chan-Muehlbauer et al, 1994). None of the four farmers use herbicides in their corn fields. For weed control they rely on extended crop rotations with alfalfa, mechanical cultivation with a rotary hoe and cultivator, and late planting of com to allow mechanical control of the first flush of weeds. One farmer reported that the com crop is cultivated three to five times. The report details the 1992 com yields at these four farms in comparison to the average yields in the same regions. In all cases, the yields of the sustainable farms were lower than the average yields in their regions. The reduced yields for the four farms were -38%, -11%, -7%, and -5%. 

A crop rotation plan must be in place to protect against pest problems and to maintain soil health. Row crops should be raised for no more than four out of five years, and the same row crop cannot be grown in consecutive years on the same land. Legumes (e.g., alfalfa, red clover, berseem clover, and hairy vetch) alone, or in combination with small grains (e.g., wheat, oats, and barley), should be rotated with row crops (corn, soybeans, amaranth. 

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... 

Rotate garden crops with green manures such as alfalfa Cover seedlings and plants with row cover or mesh, hand-pollinating squash-family plants. Apply parasitic nematodes to the soil weekly to control larvae. As a last resort, spray adults with pyrethrin. 

Many of the weed species controlled by atrazine are precisely the weed species that are not adequately controlled by alfalfa stands. While herbicide use on hay, pasture, or other crops is slightly lower than that in other rotations, the proportion of acreage treated remains at 89% (USDA ERS, 1996). Thus, many farmers who rotate into alfalfa for 3-5 years use atrazine to control weeds in a subsequent com planting. 

Across the street from my garden and our farm is a large conventional farming operation. The grower plants a rotation of wheat, alfalfa, sunflowers, and corn with an occasional watermelon seed crop. Last year the field was planted with yellow corn for... 

Soybeans are a common source of protein. They also are hard on the soils and should not be grown in consecutive years on the same field. Alfalfa is a good rotational crop for corn or beans. In some areas of the United States, alfalfa does not grow easily. In those... 

Organic crops are required to be grown in rotations, as demonstrated by the corn-soybean-oat-alfalfa rotation, shown at the I.S.U. Neely-Kinyon Farm. 

Control Remove and destroy crop residues where adults overwinter rotate garden crops with cover crops such as alfalfa cover seedlings or plants with floating row cover, hand-pollinating covered squash family plants apply parasitic nematodes to soil weekly to control larvae control adults by spraying with pyrethrin. 

---