Mulching
The term mulch as generally used means a layer of litter applied to the surface of the ground primarily for the purpose of retarding evaporation from the soil. Mulches are thus used as a substitute for cultivation to conserve the moisture in the soil in summer and to keep down weeds. They are also used as winter and spring coverings for low-growing small fruits to retard flowering and fruiting and thus to protect them from injury by late frosts. What is termed a “soil mulch” or “dust mulch” is maintained by frequent cultivation of the surface soil, and, like the ordinary mulch, is an effective means of retarding evaporation. Among the common materials used for mulching crops are straw, marsh hay, and leaves. These materials are usually applied to the whole surface of the soil in layers 4 to 6 inches deep. Mulching crops with straw or other litter is not very common. On a large scale it is too expensive. It frequently happens on a farm, however, that spring finds an old straw stack in the barnyard that will be practically valueless for feed the following winter. Can it be used profitably as a mulch?
This question was investigated quite thoroughly by the Nebraska Station. Experiments were made to determine how mulching vegetables compares with the most thorough cultivation as a general farm practice. Old straw was the material used. After settling, the layer applied was about 4 inches deep. A large number of different vegetables were grown. In general it was found that mulching in Nebraska gave much better results in normal or dry seasons than in wet seasons.
The value of the mulch in conserving the soil moisture was found to be quite marked. Soil samples taken one season in July and August showed the moisture content to a depth of 6 inches to be 18.2 per cent, as compared with 17.1 per cent in cultivated soil. When the mulch was applied early in the season before the ground became thoroughly wet, it often had a retarding effect on the growth of the vegetables. With early spring vegetables, like lettuce, which require only a few cultivations, it was found cheaper and better to cultivate than to mulch; but with longer-growing crops that require frequent cultivation throughout the season, such as cabbage, tomatoes, etc., mulching usually proved more effective and cheaper than cultivation.
The fact that most vegetables, especially the more tender kinds, can not be mulched, until they have become well established and the weather has become warm, thus requiring some preliminary cultivation, certainly increases the labor required in growing mulched vegetables over what would be necessary if the mulch could be applied earlier. But, if the impracticability of early mulching is a serious drawback to the use of mulches, so is the impracticability of midsummer cultivation under farm conditions a serious objection to dependence upon cultivation alone. For most vegetables mulching should be used to supplement cultivation rather than to displace it. Such cultivation as is commonly given farm gardens is better for most vegetables in early spring than mulching; but mulching is just as surely better in midsummer than the neglect which is the common thing in farm gardens at that time of year. The experiment station tests have indeed shown mulching to be better in many cases than the most thorough cultivation throughout the summer.
The station tests indicate that it is unwise to mulch drilled onions, lettuce, or sweet corn. The stand of the onions and lettuce is injured by mulching, while so few cultivations are required for sweet corn that mulching is hardly profitable, and in wet seasons the yield was decidedly decreased by mulching. With transplanted onions, beets, salsify, parsley, peas, and melons the labor required and yield obtained were found to be about the same by either method of culture. With cabbage, tomatoes, beans, cucumbers, potatoes, and sweet potatoes, very favorable results were secured by mulching. The yields of each of these crops were considerably increased by mulching and the labor required was considerably less than in case of cultivation alone. Mulched cabbage produced larger heads than cultivated cabbage, and there was less injury from rot. The vigor of tomato plants was decreased by mulching, but the yield of fruit increased. The fruit was also cleaner and less subject to rot. Mulched cucumbers produced perfect fruits during dry periods when the fruit from the cultivated plants was small and imperfect. The quality of potatoes was not hurt by mulching except in wet places.
In a special test of a 4-inch and 8-inch straw mulch and early and late mulching for potatoes a 4-inch mulch applied late in summer after several cultivations gave the best results. In the case of sweet potatoes the vines did not take root through the straw mulch as they do on cultivated ground, which was considered a decided advantage for mulching.
On the whole this work seems to indicate that on the farm where cultivation of the garden is likely to be neglected in midsummer, a mulch of straw can be used profitably as a substitute. For the best results the mulch should not be applied until the ground has become thoroughly warmed up and after two or three cultivations have been given. The mulch may then be safely applied to such vegetables as cabbage, tomatoes, potatoes, and beans, and the garden left to take care of itself the rest of the season.
The same plans were worked at the New Jersey stations. One season it was found that mulching increased the yield of sound fruits of eggplants 66.5 per cent and of tomatoes and peppers about 13 per cent each. The keeping quality of cucumbers also appeared to be slightly benefited by the use of a mulch. The season following, which was considerably more rainy, no advantage resulted from mulching. In this experiment there was no noticeable difference in the effectiveness of new salt hay, old hay, or excelsior as a mulch.
Several of the experiment stations have carried out experiments in mulching potatoes. The favorable results obtained in such experiments in dry seasons at the Nebraska Station have already been referred to. At the Michigan Station the following yields were obtained: Mulched, 167 bushels of potatoes per acre; cultivated, 199 bushels per acre. With another variety the yield of mulched potatoes was 252 bushels, and of cultivated, 385 bushels. The cost of cultivation was less than the cost of mulching, and the profit in both instances was in favor of cultivation. It should be stated, however, that there was a large amount of rain during this season, and that the straw used as a mulch contained a considerable amount of grain, which came up on the mulched plats, both of which conditions were unfavorable to mulching.
At the Oklahoma Station the total potato crop was increased about 50 per cent by mulching, the marketable crop nearly 100 per cent, and the size of the tubers about 70 per cent. Mulching potatoes with old shavings at the New Jersey stations increased the total number of tubers on a small plat about 16 per cent and the weight of the crop about 35 per cent. At the Georgia Station mulching potatoes with pine straw was not found to be of sufficient value to recommend the practice. These conflicting results secured with potatoes would seem to confirm the conclusion reached at the Nebraska Station that mulching is of greatest value in a dry season.
There is, however, a drawback to mulching that may not at first occur to the reader, viz., the danger it involves from fire. In dry weather a lighted match or cigar dropped upon the mulch may easily start a conflagration that it may be impossible to stop until the orchard is destroyed. It gives disaffected trespassers in the orchard an excellent opportunity to take vengeance upon the owner.
The cost of the mulch will of course depend much upon the price at which the material may be obtained. Clean wheat, rye, or oats straw would answer the purpose well, and in many localities would be cheaper than marsh hay. In some seasons oats sown as a second crop would grow fast enough to make mulching material by the time of frost. In the vicinity of marshes the coarser marsh grasses that have no value as hay may be cut after the ground freezes in autumn and would make excellent material for mulching. Cornstalks have been suggested, but they are probably too coarse to keep down weeds.
It has been suggested that by sowing rye in September, and harvesting the crop the following June, and then sowing the same ground to millet, the rye straw with the millet would mulch an area of plums equal to that on which the two crops were grown, and would leave the thrashed rye to compensate for the labor. This is certainly worth trying by those who have no better source from which to obtain mulching.—(Nebr. Sta. Bul., 79, 80.)