Research at the Northeast Louisiana Experiment Station showed that the use of winter legumes as green manure crops increased the yield of cotton from 1 bale to 1.5 bales an acre and maintained the high yield over a period of 23 years. After turning under good growths of winter legumes for 3 years in succession, the beneficial effect extended to the following second and third cotton crop. The application of 30 pounds of nitrogen an acre at the time the green manure crop was turned was profitable.

Studies in North Carolina disclosed that a good crop of Austrian peas or vetch produced as much cotton as 80 pounds of commercial nitrogen. No significant increase in the yield of cotton was obtained from 120 pounds of nitrogen as compared to 80 pounds or when 20 or 40 pounds of nitrogen was added to cotton following Austrian peas or vetch.

Workers at the Pee Dee Experiment Station in South Carolina reported that in 3 years out of 5 difficulty is experienced in obtaining and maintaining the stands of cotton following green manure crops, particularly when weather conditions are adverse.

Results of experiments studying the effect of green manure crops on the yield of cotton may be summarized thus: The beneficial effect of green manure crops is related to the nitrogen supplied by the crop. This tends to eliminate nonlegumes as green manure crops. Annual winter legumes have been found equal to 80 pounds of commercial nitrogen in producing cotton. It often is necessary to delay the turning of a winter legume in order to obtain sufficient growth. This may result in planting cotton too late for maximum production.

Research workers in States in which peanuts are grown commercially usually recommend that green manure crops follow the peanut crop. The Alabama Station compared peanuts in a 2-year and a 3-year rotation for 10 years at two places. The yield of peanuts in the rotation cotton-peanuts was 1,349 pounds an acre. When the rotation was cotton-winter legumes-peanuts, the yield of peanuts was increased 130 pounds. In a 3-year rotation cotton-winter legumes-peanuts-winter legumes-corn the yield of peanuts was 134 pounds more than the 2-year rotation without legumes.

Several winter annuals were tested in a cotton-peanut rotation at Rocky Mount, N. C. Average yields for a 6-year period indicated crimson clover, vetch, ryegrass (plus 18 pounds of nitrogen), and Austrian peas, in that order, were effective in increasing the yield of peanuts. In 2 years out of the 6 years, none of the green manure crops produced a significant increase over the crop without green manure.

The Georgia Coastal Plain Experiment Station has recommended the use of green manure crops in peanut rotations. It is suggested, however, that the green manure crop precede corn, cotton, or some other crop that can use large amounts of nitrogen more effectively than peanuts can.

The evaluation of green manure crops in the production of peanuts can be summed up in this way: The peanut, a legume, can obtain part or all of the needed nitrogen from the atmosphere when it is properly inoculated. Large amounts of nitrogen en may be detrimental to peanuts. In order for fruits to be formed, the peanut peg must penetrate the surface of the soil. Measurements made after green manure crops are turned indicate that they made the soil less compact and more easily penetrable. The use of green manure crops preceding peanuts may result in increased damage from diseases, insects, and nematodes.

In considering the influence of green manure crops on tobacco, one must take into account the effect on yield and quality. A 7-year experiment in Maryland showed that the highest yield and the best quality tobacco was produced when tobacco was grown following ragweed turned in the spring. The lowest yield and quality was produced when tobacco followed lambsquarter. Lespedeza produced a fairly satisfactory yield, but it was of low quality.

An experiment in North Carolina compared the effect of vetch, crimson clover, fallow, cowpeas, soybeans, and lespedeza on flue-cured tobacco. Vetch and crimson clover resulted in lower quality and acre value. There were no striking differences in the other.

These and some other experiments are summarized thus: Flue-cured tobacco should not be grown immediately following a leguminous crop. The amount and availability of nitrogen is too difficult to control. Some weeds appear to exert a favorable influence on the yield and quality of tobacco. Others exert an unfavorable influence. Management of the green manure crop will affect its influence on tobacco. Rye turned late may tie up nitrogen during the early part of the tobacco season and release it late in the season, causing an inferior quality of tobacco. Certain green manure crops may result in an increased damage to tobacco from diseases and pests. Crotalaria and velvet beans appear most effective of the legumes tested in reducing damage by nematodes.

GREEN MANURE CROPS often are used in vegetable rotations. The effects of various organic matter additions on yield of potatoes in a 2-year rotation were studied for 16 years in Maine. Green manure increased the yield of potatoes an average of 53 bushels an acre. When the green manure crop was removed, the yield of potatoes was reduced 38 bushels, as compared to turning the crop.

Another experiment in Maine showed that legumes increased the yield of potatoes considerably more than non-legumes. Eighty pounds of commercial nitrogen was applied in both of these experiments.

L. M. Ware and W. A. Johnson, of Auburn, Ala., studied the value of vetch with and without commercial nitrogen. During a 6-year period, they obtained only 3 bushels of snap beans an acre when no nitrogen was used. Snap beans following vetch produced 161 bushels. When 60 pounds of nitrogen was applied, the yield was 144 bushels. Similar results were obtained with lima beans and eggplant. They reported that the average value of the organic treatment on all vegetables studied was 135 dollars an acre above the cost of the practice.