SOME CROPS FOR FODDER

OF THE soilage crops, Napiergrass is most commonly used because of its long life, ease of production, and remarkably high yields. It is grown as cut forage almost entirely in zones A, B, and C, under irrigation. The average yield at the University Farm in Honolulu through 3 years was 71 tons of green forage to the acre each year.

Yields of 50 tons for a single crop have been recorded; one dairy, which had 500 cows and produced most of its roughage requirements on 35 acres of Napiergrass, reported 150 tons. This grass requires ample water and fertilizer for heavy yields. A 75-ton yield would remove from the soil the equivalent of 1,200 pounds of ammonium sulfate, 500 pounds of superphosphate, and 1,500 pounds of potassium sulfate. Many soils will provide sufficient available phosphorus and potassium for a long period, but nitrogen soon becomes the limiting factor in production on most soils.

Napiergrass is not a high-quality forage; it commonly contains about 4 percent protein on a dry basis. Cut at an immature stage, it may contain as much as 15 percent protein. At this stage, however, the dry matter content drops from the normal of about 20 percent to 10 or 12 percent; while the palatability as well as total production of protein increases, the production of dry matter per acre per year drops. Hence, it becomes a question between lower production of better and more palatable forage, or higher production of less desirable feed with a greater annual total of dry matter and total digestible nutrients. Digestibility trials show that 59 percent of the dry matter even of mature Napier is digestible.

Paragrass is grown for cut forage in zone D₁ without irrigation. When grown on good soil and adequately fertilized, it can be cut as often as every 8 weeks. At the University Farm it produced 46 percent more digestible crude protein than Napier, with essentially the same yield of total digestible nutrients. It is palatable, and some dairymen believe it is a better milk producer than Napiergrass. It can be readily cut with a power mower, and gathering and feeding the cut forage is somewhat easier than with the coarse Napier-grass. Para and Napier make up probably 90 percent of the grass roughage cut for the dairy herd.

Sudangrass once was extensively planted, but now it is of little importance. Its rather rapid decline in yields of successive ratoon crops and susceptibility to rust during the winter months are its principal weaknesses. The crop has much to commend it: It is readily established by seed, and produces its first crop about 2 months after planting. It recovers rapidly, and as many as 8 cuttings during the first year, with a total annual yield of 49 tons an acre of green forage, have been obtained at the University Farm. Tests at the University showed that Sudan-grass was the only one of several grasses that gave significantly higher milk production.

Sugarcane tops or the entire plant if it is cut at an immature stage make excellent roughage. One dairy that grows sugarcane for the purpose reported increased milk yield over that produced by Napiergrass. Strip cane and pineapple pulp, byproducts of the sugar and pineapple industries, are also fed as fresh roughage.

The only legume grown widely for soilage is koa haole. Many dairymen were reluctant to use it because of its depilatory effect on nonruminants; they feared also that it might affect reproduction and produce off-flavors in milk. Investigations at the Hawaii Agricultural Experiment Station showed that the depilatory effect is due to the compound mimosine and not to selenium, as was supposed. The experience of several dairies seems to justify the conclusion that koa haole is a safe and nutritious feed for dairy cows. Milk production trials at the University Farm have shown that 55 pounds of fresh koa haole a day for each cow provided enough digestible protein to replace all the soybean meal in the supplemental feed, with no significant lowering of production.

Since the plant normally grows as a woody, treelike, stemmed shrub, the Hawaii Agricultural Experiment Station undertook experiments to determine aspects of establishment, culture, frequency of cutting, height of cutting above ground levels, and moisture requirements. We found that in most respects it is hardy and adaptable and can be handled much like any other perennial row crop. It grows slowly at first, and from 6 to 9 months are required before the first cutting can be made. The optimum yields are at about 4-month intervals when the new growth is about waist high. Cutting at 2 to 4 inches above ground level gives yields essentially the same as at higher levels.

Forage yields have not been exceptionally high, however. At the Pensacola Station in Honolulu, 25 tons an acre a year of green forage and 2,700 pounds of protein per acre were produced. At Poamoho Farm, at an elevation of 700 feet, only 18 tons were obtained. Probably that is the maximum altitude for its practical use as a soilage crop. One of its most valuable characteristics is its ability to produce good forage yields without irrigation, where the natural rainfall is as little as 3 to 4 inches a month. Under similar conditions Napiergrass requires irrigation every 10 to 12 days.

The power-driven corn binder can be used without change to cut koa haole. In fact, hand cutting of the crop is so laborious and expensive that its production would not be feasible without the corn binder.

Alfalfa used to be planted rather extensively as a cut forage crop. Yields for the first year of 60 tons of green forage have been had with a cutting interval of 4 to 5 weeks. An average of 37.5 tons was obtained from eight plantings at the University Farm. Despite such yields, the crop is grown on a limited acreage now, primarily because of its relatively short productive life and the high labor cost of removing noxious grasses from the stand. It is possible that use of tractor-mounted disk cultivators and selective weed sprays may solve the weed problem economically. With proper equipment, 4 field can be plowed and planted to alfalfa and harvesting begun on the new field in about 5 months. Alfalfa would be a welcome addition to the dairy ration in Hawaii.

The total area devoted to soilage legumes is small, probably less than 5 percent of that in soilage grasses. The main reason is that grasses like Napier will produce a much greater annual yield of dry matter and total digestible nutrients an acre than will legumes. For example, a yield of 80 tons an acre of Napiergrass contains about 20,000 pounds of total digestible nutrients, with a nutritive ratio of 13.3, while a 25-ton yield of koa haole contains only 8,590 pounds of total digestible nutrients, with a nutritive ratio of 3.3. This higher production is important, because most dairies here have available only a limited amount of good, arable land. The use of these grasses with such a wide nutritive ratio requires relatively large amounts of costly imported concentrates to balance the ration.

THE AUTHOR--J. C. Ripperton, a graduate of Kansas State Agricultural College, has lived in Hawaii since 1920. He has investigated many tropical crops and their relationship to the general problem of diversified agriculture in Hawaii. He has been associated with tropical forage crop and pasture research since 1930. He is the agronomist of the Hawaii Agricultural Experiment Station, University of Hawaii.

E. Y. Hosaka, assistant agronomist, and M. Takahashi, junior agronomist, of the Hawaii station, provided data and helped prepare the manuscript.