Special Uses

Soil Management for Pastures

R. R. Robinson, R, E. Blaser, and H. B, Peterson.

Pastures are grown on very good and on very poor soils. Their fertilization, plant species, and grazing management vary accordingly.

A large acreage of pasture is on land too rough, steep, poorly drained, or otherwise unsuited for tilled crops, but such pastures occasionally may be renovated to introduce higher yielding species. Good management is particularly important because productive pastures should be kept as long as possible before renovation again becomes necessary.

Soils that are rough, steep, stony, or wet may be utilized for truly permanent pastures. The pasture species on them will be those in equilibrium with soil conditions, climate, and grazing management.

Irrigated pastures in the West often are seeded on some of the best soil. Much of the acreage, however, is on soils that are hard to cultivate. They are poorly drained and contain salt and alkali.

Some forage plants are well adapted to these adverse conditions and can be productive with proper management.

Tall wheatgrass or tall fescue, for example, tolerate saline and alkali conditions. Planted in the bottom of furrows or with a deep-furrow drill, they usually will become established and produce considerable forage of fair quality. They also improve the physical condition of the soil and facilitate leaching of the salts if drainage can be established. After such growth, it is possible to introduce more desirable species.

SOIL MANAGEMENT for pasture establishment varies widely, depending on the soil conditions and on the pasture species or mixtures to be sown.

Pastures in a regular crop rotation are seeded on land that is already plowed and fitted for a good seedbed. Seedings may be with or without a companion crop of a small grain. A companion crop is desirable on soils that crust easily and on those where wind damage is a hazard. Experiments by G. H. Stringfield and L. E. Thatcher in Ohio and by investigators in other Midwestern States have shown that successful seedings can be made directly in corn if the corn rows are spaced 5 to 7 feet apart.

Experiments conducted by J. L. Haynes and Dr. Thatcher in Ohio and substantiated by experiments in Michigan, Pennsylvania, and other places showed that better stands and more vigorous seedlings can be obtained by drilling phosphate fertilizer in narrow bands at a depth of about 1.5 inches and seeding directly above it. Band seeding was done in the early experiments with a grain drill, in which the tubes from the grass seedbox were extended so that the seed was dropped directly over the band of phosphate. Placing the phosphate directly below the seed seems to be particularly desirable on soils low in fertility and when the weather is apt to be unfavorable. In seedings made late in the season on poor soils, the increased growth resulting from placing the fertilizer near the young seedling may mean the difference between failure and success.

On highly fertile soils, band placements appear to have little if any advantage over conventional methods of fertilizer application.

Certain precautions must be observed in banding fertilizer for grasses and legumes. Because the young roots grow straight down with little branching during the first few weeks, the fertilizer must be directly below the seed but the roots will be burned if the salt concentration in the band is too high. There is no danger of burning from phosphate fertilizers, but potassium and nitrogen should be used sparingly in the band, particularly if the seeding is likely to be followed by dry weather. Additional potash, if needed, should he mixed with the soil.

RUNDOWN PASTURES on land too rough or too steep to plow have been improved by renovation. The old sod is broken up, lime and fertilizer are added, and adapted grasses and legumes are seeded. Pasture renovation is used on poor sods and on dense grass sods from which legumes have disappeared. In either case, but particularly on the good sods, the roots must be cut so that the grass will die; otherwise the new seeding may be crowded out by the rapid regrowth of the old sod.

An annual may be planted for a season on land that is not too rough. That allows for further tillage and better eradication of the old sod before establishing a permanent pasture mixture.

A heavy cutaway disk, often called a bush and bog harrow, is particularly effective for pasture renovation. A heavy field cultivator also may be used, although on heavy sods it may roll up the sod if the shovels are not widely spaced.

Grasses are hard to kill by tillage in the late fall or early spring because the old sod recovers rapidly if it has enough moisture. During hot, dry weather, on the other hand, the soil is so hard that tillage is ineffective. The ideal time to disk is immediately after a heavy rain early in the summer. Even then one will have to disk again after 2 or 3 weeks.

Experiments at several stations show that some of the new herbicides (such as Dalapon) are effective in killing the old sod. Most of the experiments indicate that a combination of herbicides and tillage may be more satisfactory than either alone. The herbicide, even if it does not kill the grass, will make tillage easier and more effective.

Probably the choice of a herbicide will be determined by the species of grasses or weeds in the pasture, weather conditions, and the cost of the material.

Fertilization and seeding practices are similar to those on tilled land except that the rate of phosphate fertilization should be greatly increased on most pastures not previously renovated or fertilized. Erosion usually is not a problem because the old sod is an effective mulch.

Kentucky bluegrass is one of the few pasture species in which establishment is not a problem. In the Northern and Eastern States, fields that are limed, fertilized, and managed as pastures ultimately will become Kentucky bluegrass pastures, with varying amounts of whiteclover. In fact, for years the standard practice for improving old poverty-grass and broomsedge pastures was to topdress with lime and fertilizer. Within 2 or 3 years after fertilization, a vigorous volunteer stand of Kentucky bluegrass and whiteclover crowds out those poor-land grasses.

THE IDEAL PASTURE consists of nearly equal stands of grasses and legumes. Lime and fertilizer are essential for soils of the Eastern States in attaining this ideal mixture.

Fertilization is complicated, however, by the fact that the species, grown in close association, vary in fertilizer requirements, habit of growth, and response to grazing management. That may seem confusing at first, but in practice it is a matter of maintaining the legumes by fertilization and grazing management. On soils where legumes are not well adapted, however, it is more practical to grow grasses alone than to attempt to maintain legumes.

Fertilization for grasses is quite different than for grass-legume mixtures. Most of the State experiment stations have bulletins giving details that should be followed for local conditions. Besides more common fertilizer elements, the application of some boron is recommended for alfalfa in the Eastern States. Deficiencies of sulfur occur in some parts of the West and the South. Deficiencies of other trace elements in pastures have been reported.

LIME applied to pastures penetrates the soil very slowly. On acid soils it is therefore particularly desirable to work lime into the soil before seeding. The maintenance requirements of the pasture for lime can be met by topdressing, based on soil tests. The amount will depend on weather conditions, the soil, and the productivity of the pasture. Generally it is less than on tilled land.

THE IMPORTANCE of phosphate fertilization for legumes is well known. It has taken some time for its value for grasses to be generally recognized, however, partly because we did not realize the interrelations of nitrogen and phosphate fertilization.

Pure grass sods are low in available nitrogen. Phosphate fertilization of an old grass pasture, even though the soil is low in available phosphate, gives little increase in yields because of the low level of available nitrogen. If nitrogen is applied, however, the response to phosphate is remarkable.

Phosphate fertilizers on pastures are not lost through leaching, and the losses in crop removal are relatively small. The rates of application depend largely on the amounts of available phosphate in the soil and the productive potential of the land. The frequency of application of phosphate is not important on most soils. For example, 120 pounds of phosphoric oxide-P₂O₅ an acre every third year or 40 pounds of P₂O₅ an acre every year, are nearly equally effective. If phosphate is the only fertilizer applied, therefore, it is cheaper to apply heavier rates at longer intervals and so save the costs of spreading it.

POTASSIUM behaves quite differently from phosphorus both in the soil and In the plant, and fertilizer practices differ accordingly.

A high-producing pasture requires 100 to 150 pounds of potash an acre annually. It can absorb as much as 400 pounds. This extremely high absorption luxury consumption of potash is a waste of potassium, as it serves no useful purpose to the plant or the grazing animal. Potash fertilization is necessary for good pastures, but the rate should not be excessive.

Over a period of years, pastures as compared to meadows need considerably less potash because all of the potash in the hay is removed, whereas the grazing animal removes only 20 to 25 percent.

An illustration is provided in experiments by B. A. Brown in Connecticut. On a field that had been grazed over a period of years, potash gave no increase in yield. On an adjoining field cut for hay, the level of available potash in the soil was so low that legumes could not be grown without liberal applications of potash.

Luxury consumption of potash is much greater in grasses than in legumes. R. E. Blaser and N. C. Brady, in experiments at Cornell University, found that Ladino clover on a soil low in available potash contained 0.96 percent potash, compared to 1.96 percent for grasses growing in association with the clover. Liberal fertilization increased the potash content to 2.47 percent for Ladino clover and 3.18 percent for the grass.