In grass-legume mixtures, potash must be applied to meet the needs of the legume even though there may be some luxury consumption by grass.

Potash should be applied twice a year on many soils. On sandy soils, particularly those where the growing season is long and yields are high, more applications may be needed.

Legumes show easily recognizable symptoms of potash deficiency white spots along the margin of the leaves, followed by yellowing of the leaf margins and eventually the entire leaf. Potash deficiencies often can be detected and additional fertilizer applied in time to save the legume.

The emphasis on potash for legumes has sometimes led to the wrong conclusion that grasses do not require potash fertilization. Because grasses remove more potash from the soil than legumes, they deplete the soil faster.

In experiments at the Regional Pasture Research Laboratory, pure stands of alfalfa and of orchardgrass were grown with and without potash fertilization. All plots received lime and phosphate. The grass received nitrogen fertilizer. The increase in yield from potash fertilization was higher the first harvest year for alfalfa than for orchardgrass. By the third year, however, the increases in yield from potash fertilization were higher for the orchard-grass than for alfalfa.

The application of potash is not common on irrigated pastures west of the Missouri River. The soils generally are well supplied, or the water contains considerable potash. Fertilizer should be applied if soil or plant tests indicate a need for it on a particular farm.

NITROGEN fertilization of pastures can be expected to become more and more profitable. The greatest returns will be from pure grasses on soils not suited to maintenance of legumes and on good soils where it may be desirable to maintain pure grasses for a time following loss of legumes.

The amount of nitrogen used depends on the need for pasture on the particular farm and on soil and climate. Under favorable rainfall and a long growing season, nitrogen may well be applied several times a year at rates exceeding 200 pounds an acre a year.

Nitrogen fertilizer is used on good grass-legume mixtures only in special cases for example, to provide for early spring grazing. Because most grasses grow earlier in the spring than legumes do, nitrogen fertilization can be used to stimulate earlier growth. Only a small field usually is fertilized for this purpose, and the grass is grazed early to avoid crowding out the legume.

Many grass-legume mixtures have only fair stands of legumes, and nitrogen fixation is not adequate for high production. It is desirable then to use nitrogen fertilizer to supplement the nitrogen fixed by the legume plants. Then grazing must be carefully controlled and on most soils in the East additional potash must be applied to prevent the grass from crowding out the legume.

SUPPLEMENTAL IRRIGATION is one possible solution to the problem of providing abundant high-quality pasture during midsummer.

Increases in pasture production from irrigation were reviewed by John R. Carreker and James H. Lillard in Water, the 1955 Yearbook of Agriculture. Under irrigation, adapted forage crop species adequately fertilized can be expected to produce about 50 pounds of dry forage an acre a day during midsummer. Without irrigation, yields may drop off to zero for short periods. The increase from irrigation, therefore, may range from 0 to 50 pounds of dry matter an acre a day.

Rotation grazing of irrigated pastures is an integral part of soil management. Irrigation water should be applied after the animals are removed from the pasture. The movement of the animals over the wet lands is harmful to the plants and tends to puddle the soil. Moreover, the plants recover more rapidly following grazing if water is adequate.

On many farms the available water supply is not adequate for irrigation. On others, the anticipated returns may not justify the cost. But it is possible to increase midsummer grazing through the use of adapted species and suitable grazing management.

Alfalfa is particularly well adapted to hot, dry weather. In most years it makes excellent growth during midsummer. With proper management, it may be grazed without injury to the stand.

The growth of adapted grasses can be increased greatly during midsummer by proper fertilization. If the soil is well fertilized, growth will start immediately following a rain and will continue until moisture is depleted.

At low levels of soil fertility, water will be transpired at almost the same rate, but growth will be poor even when moisture is adequate.

In an experiment conducted in Pennsylvania during 2 successive years of subnormal rainfall, R. R. Robinson and V. G. Sprague obtained an average of only 415 pounds of dry matter an acre during July and August from an orchardgrass sod on a good soil. Liberal amounts of nitrogen fertilizer increased the average yields to 1,575 pounds. Fertilization and irrigation raised the yields to 2,750 pounds. Even though rainfall was below normal and yields were limited by dry weather, it was possible to increase midsummer production by adequate fertilization.

CONTROLLED GRAZING is essential for high production of forage crops. All forage crops after clipping or grazing draw upon stored carbohydrate reserves in starting new growth. The reserves are replenished as the plants recover. Various grasses and legumes differ in the extent of depletion of reserves after clipping and in the rate of recovery. Alfalfa is particularly susceptible to continued depletion of root reserves and must not be grazed or clipped too frequently.

The responses of Ladino clover, however, are quite different from those of alfalfa. The stem of Ladino clover grows along the surface of the ground and a leaf develops at each node. When growing with a tall, vigorous grass, each new leaf of clover arises in rather dense shade; under such conditions, new growth draws heavily on the plant reserves. This weakens the plants and may lead to complete loss of the clover.

Highly significant, however, is the fact that Ladino clover stores carbohydrate reserves in the prostrate stems, but the grasses store a large part of the reserves in the lower part of the stem. Thus close grazing actually will remove part of the reserves of the grass but not of Ladino clover. Frequent grazing to hold the grass in check is essential to maintain Ladino clover in a mixed sod. That is particularly important if the grass has been stimulated by nitrogen fertilization.