Our Sources of Seeds of Grasses and Legumes

HUGO O. GRAUMANN.

SEVERAL hundred varieties of grasses and legumes comprising more than 125 species have economic importance in the United States.

They differ in performance and in their requirements as to soil and climate. At least one variety is adapted to each use and to each particular site or location. Grasses and legumes therefore are an important part of the cropping system on nearly every farm.

Permanent stands of grasslands, including hayland, pastures, and ranges, comprise about a billion acres in the United States.

The various species are grouped as perennials, biennials, and summer and winter annuals. The longer lived species generally have the widest range.

Alfalfa is most widely grown of all cultivated forage species, primarily because of the success of plant breeders in developing numerous varieties that differ markedly in growth response, cold endurance, and persistence.

We estimate that 8 to 10 percent of our grasslands are planted each year to replace acreages on which either a grass crop has passed maturity or is plowed under as a phase of crop rotation. For replanting those acreages and seeding other land, nearly 1 billion pounds of seeds are needed annually.

A highly specialized seed-production industry is essential to assure domestic supplies of seed that have the specific superior genetic characters that differentiate the recommended varieties one from another.

Several developments have caused shifts in the regions of seed production.

Many meadows and hayfields that had been sources of seed of local strains of grasses and legumes were put under the plow in the war years and planted to cereal and feed grains. The mechanization of many farming operations and economic problems changed many agricultural practices. Specialization in corn, soybeans, wheat, and other cash crops grew. Soil conservation practices caused some shifts in the use of land. Increasing numbers of livestock meant that many of the remaining meadows once used for both forage and seed were set aside for pasture and hay only. The demand for forage seeds of improved varieties has grown.

Imports of legume and grass seed before 1930 were relatively large. For several years we imported annually 40 million pounds of alfalfa and red clover seed. One year we imported 11 million pounds of alsike clover.

At one time, practically all the bahiagrass used in the South was imported. Our need now for this species is met almost entirely with domestic seed of improved varieties, which are superior in winter hardiness, persistence, and yield.

The total imports of forage seeds has dropped since 1930, primarily because of substantial increases in the domestic production of seed. Nevertheless, relatively large amounts of seed of sweetclover, crimson clover, birdsfoot trefoil, fescue, and orchardgrass were imported from overseas in 1960.

Most of the grasses and legumes available to farmers before the Second World War were the result of importations or seed increases of locally adapted types selected from introduced or native materials. Varieties were uncommon. The production of grassland seed was a minor enterprise on many farms.

Local customs dictated most of the production practices. The preferred or best adapted crop usually was grown, primarily for forage and soil conservation; when the weather was favorable, a seed crop was produced and harvested from a meadow or hayfield.

In those instances where varieties existed, little effort was made to maintain foundation planting stock and to minimize the chances of genetic contamination from cross-pollination with other varieties growing nearby. The characteristics of ecotypes and varieties therefore kept undergoing change from one generation to another. This gave rise to an increasing number of local strains, which were superior to imported seed.

Whereas seed once was a byproduct, a trend started about 1948 to plant exclusively for seed production. Such enterprises, to be most profitable, must take close account of the requirements as to climate, soil, and management of the variety.

Winter annuals usually do best where winters are relatively mild.

Some summer annuals are adapted to the South and others to northern latitudes. A generally favorable climate for most perennial species is characterized by winter conditions with near-freezing to freezing temperatures at night; a relatively rain-free growing season of 180 to 200 days; and clear, sunshiny days, with optimum daytime temperatures during set and development of seed ranging from about 75 F. for the cool-season grasses to approximately 95 for most perennial legumes.

Pollinating insects, such as bees, are essential for most legumes. These insects are relatively inactive on cloudy days and at temperatures below 70 .

The length of day required for flower initiation varies among and within species. The cool-season grasses and northern-adapted alfalfas and clovers usually blossom most profusely and according to schedule in the more northern latitudes under conditions of low night temperatures in spring and long, warm or hot days in summer.

As these grasses and legumes are moved south (into regions of shorter days) for production of seeds, many plants in normal populations of given varieties are retarded in both initiation and profuseness of flowering, particularly if night temperatures in spring are not low enough to fulfill the variety prechilling requirements for flower initiation. The unwanted genetic shifts that result cause changes in the characteristics of a variety.

GREAT PROGRESS has been made in breeding improved grasses and legumes since 1940.

The development of new varieties with disease resistance and tolerance to a greater range of temperatures and improved management technology have permitted the extension of some species of legumes and grasses into new regions and soils previously unsuited to grassland and agriculture.

The growing interest in grassland farming meant that the demand for forage seeds could no longer be met by the older methods of producing seed from hayfields. The total yield of seed had to be increased and greater care had to be taken to guard against genetic shifts caused by effects of daylength, temperature effects, and outcrossing to other varieties and sorts.

Seed production had to advance from a minor to major farm enterprise.

The success of such an enterprise rests on proper management row planting with proper isolation of fields, timely irrigation, forcing plant growth to flower when temperatures are favorable, adequate control of insects and weeds, satisfactory pollination, and timely harvest. Farmers who were willing to make seed production a primary business achieved success.

Production shifted to new sections. Bluegrass, alfalfa, and the bentgrasses are examples.

Kentucky and parts of adjoining States before 1920 produced more than half of the seed of Kentucky bluegrass harvested in the United States. Insect damage to old fields and declining soil fertility caused a shift to Missouri, Iowa, Nebraska, South Dakota, and North Dakota, which in 1960 produced more than 80 percent of our seed of Kentucky bluegrass.

Frequent summer rains in the Corn Belt and farther east, and sustained demand for hay were deterrents to the production of alfalfa seed. The primary sources of seed were the Great Plains and Intermountain regions, and until recently seed production was considered mostly a byproduct of hay production even in those sections. The production of alfalfa seed has mushroomed since 1945 in the West, where water for plant growth can be controlled by irrigation.

The bentgrasses once were important in pastures in the eastern New England States and later in turf plantings. For many years the seed was harvested in late summer from pastures that were grazed in spring and early summer. The seed, however, came to have so many weed seeds that bentgrass seed harvested from the established areas became unsuitable for lawn, golf courses, and other turf.