Wool Quality Depends on Soil Fertility
THE GEOGRAPHIC LOCATION of sheep puts them dominantly on drier soils. Natural survival of them seems to be high in regions of lower rainfall, where soils are less leached of their fertility. Hence, it is on the soils richer in lime, and on grasses grown where calcium and other soil-given nutrients are active in both the soil and the plants, that we find the best reproduction and growth of these producers of both wool and meat. That their wool manufacturing business, like their meat making activities reflect the differences in soil fertility is not so commonly appreciated, even if we have the different breeds for the fine and the coarse wools in different climates and therefore on different soils. But when the same soil in adjoining plots given different fertilizer treatments makes different wool on the back of animals of the same breed, in the scouring vats and in the final carded fibers, we must come to consider the fertility of our soils as a factor in controlling the quality of the wool. Better wool from better soil may be a new slogan to bring the wool producer of the humid region, at least, to consider economic and efficient wool production in terms of soil fertility. This is the suggestion that comes from some experiments testing sheep responses to soil treatments.
In an attempt to use a smaller ruminant than the cow to measure the possible improvement in feeding value of lespedeza hays in consequence of the treatments of superphosphate and lime on the soils growing them, sheep were chosen as the test animal. The lespedeza hay was the legume companion crop of wheat in some of the soil studies of the experiment station. Three plots were involved of which one was given no treatment, one had superphosphate on the wheat at fall seeding, and one the same amount of phosphate but as an addition to limestone on the soil. The wheat was harvested in June and the lespedeza in the stubble made into hay in August to be used as the sheep feed in the dry lots.
Since the plot with no soil treatment produced too little lespedeza hay to carry a significant number of sheep for a good number of days, it could not be used in the first trials. Feeding tests were consequently made with only two lots of lambs. One of these lots was fed on lespedeza hay grown on soil given phosphate, and the other on hay grown where both phosphate and lime were the soil treatments. The grain supplements of corn and bran and all other features of management were the same for the two lots of sheep kept in adjoining pens.
Since the aim was not that of fattening the sheep, but merely one of carrying some weanling lambs through the winter on a moderate amount of feed, only a small daily allotment of grain was given while the hays were fed liberally. The hays were not completely consumed. The unconsumed portion was weighted and careful record kept of the amount taken under a liberal selection by the lambs that left coarser stems and other plant parts. The lambs were put under the experiment on mid-September and carried through until March.
Differences in appearances of the two flocks were detectable before any pronounced differences were shown by the weekly weighings. Those fed on the hay grown where phosphate only was the soil treatment appeared to have cleaner wool, their tops were smoother and there was the general finer wool appearance. Those lambs taking the lespedeza hay grown where both limestone and superphosphate had been the soil treatment appeared as if the wool were not so clean. Their tops were more rough to suggest the effects of more severe weather. These differences persisted and became more pronounced as time passed.
When the animals were given closer study by opening their fleeces, the much more abundant yolk was evident on the rough appearing lambs feeding on the hay grown on the land given lime and phosphate. (Figure 1). The differences in body weights, too, were emphasizing the greater efficiency in animal growth per unit of this hay consumed. When the yearlings were shorn in the spring, samples of wool were collected from the corresponding several parts of the body as the fleeces were weighed and found to be slightly heavier in case of those from the sheep on the hay given both lime and phosphate as the soil treatments.
More significant, however, than any difference in yolk contents of wool, or weights of the fleeces, was the behavior of the wool samples during scouring in dilute alkali solutions. Those from the fleeces with little yolk, or from animals consuming hay grown on soil given phosphate only, seemed to collapse, and appeared as if the fiber were almost a colloidal or jelly-like form. Those samples with much yolk, or from those sheep fed on the hay grown on limestone and superphosphate as the soil treatments, stood up in the scouring liquid to retain their fibrous appearance. When the wool samples were finally rinsed out, carefully air-dried, and carding attempted, those originally with much yolk carded into the usual fluffy, resilient condition of carded wool. Those originally with little yolk coming from the animals given hays with phosphate only could not be carded without breakdown of the fibers.
Fig. 1—Differences in the appearance of the wool and in the yolk of the fleeces of the sheep according as they were fed lespedeza hay grown on soil given phosphate only (above) or both lime and phosphate (below).
Here then, is a distinct reflection in the output by the woolmaking part of the sheep. of a decidedly different physiology of those same animals excreting much yolk at the same time they were growing wool on feed from soil stocked with limestone and phosphate. Their output is in contrast to those giving little yolk and wool fibers that did not stand up under scouring in consequence of feeds grown on soil given phosphate but no limestone.
Difference in wool quality in these cases was not due to a difference in breed, nor to a difference in animal age, and not to a difference in plant variety in the feed. It was due to a difference in the soil fertility occasioned by so little as the few hundred pounds of superphosphate combined with the few thousand pounds of limestone put on the millions of pounds of soil per acre. These changes in the physiology of the life of the soil came through as changes in the physiology of the same kind of plants as hay, as changes in the physiology of the sheep eating it, and as decided differences in the quality of the product for which sheep are particularly grown, namely, the wool.
We have not concerned ourselves too seriously about the soil fertility needed to grow animals, when we are thinking of simply going to extensive pasture farming as a soil conservation measure intended to master the problem of soil erosion. Erosion is most serious in regions of high rainfall. It is disastrous in soils that have been cleared of their original timber crops. It is devastating on these soils that are naturally already leached of their lime and other fertility elements, and that have their much more leached and much less fertile subsoils coming up through erosion to be the surface soils. It is on just such soils where much of the pasture farming is to be the rejuvenation for the farms and is to present a new economy by means of animals harvesting the crop cover hopefully saving the soil.
We need to remind ourselves that sheep, like cattle are most prolific and productive with minimum of attention in the regions of lower rainfalls and where the soils are still amply stocked with lime and corresponding mineral plant and animal nutrients. It is in what may well be called the “Midlands of the U.S.” that prize animals are produced. It is on the regions of rainfall so low as to make short grass that sheep are well nourished on pastures. It was on these same areas that “Buffalo grass” abounded, or that more scanty vegetation on which the buffalo located his herds and survived. If extra tonnage of feed per acre or minimum of roam to gather it had been his objective surely he would have left the short grass country and gone eastward into the bluestem regions.
Natural animal distributions are pointing to the differences in the fertility of the soil as the basis for the differences in nutritional services of the forages to the animals. Soil treatments in the more humid regions are helping us to understand that it is animal nutrition that determined the distribution. They are demonstrating that animal reproduction, animal growth, and animal output of their products such the wool of the sheep depend on the fertility of the soil reflected in the feed. The animals are, and perform as they are fed. Feeding is not so much a matter of large amounts consumed, but a matter of the quality of the feed taken which as hays and forages goes back to the fertility of the soil where they grew. Wool is an animal crop and in the last analysis, it comes from the soil too. Its quality, therefore, depends on the soil fertility.