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Effect of Methods of Grazing on the Yield of Lucerne

H. W. Turpin

 

THOUGH lucerne is usually described as being the king of hay crops, seldom is it referred to as a valuable pasture plant, excepting for pigs and possibly horses.

The chief reasons advanced again the use of lucerne for grazing purposes are (a) that it causes hoven in ruminants and (b) that the crop will soon be destroyed if closely pastured. In spite of these arguments, however, we find that lucerne is seldom used solely as a hay or soiling crop and grazing is fairly generally practised, especially in certain districts, while we frequently hear of the tremendous advantage that the Argentine enjoys in her ability to graze cattle on lucerne without fear of bloat.

Undoubtedly there are many reasons why the grazing of lucerne can be commended, the chief of which are (a) the saving of considerable expense associated with the harvesting and curing, and (b) the inducement to use the crops on the farm as a feed instead of succumbing to the temptation to sell when prices for hay are high.

On the other hand, the risk of loss of valuable animals from hoven and the injury to the stand of lucerne by injudicious grazing is strong deterrents to the more general use of this crop for pasture purposes.

 

Experimental Data

In view of the advantages of grazing lucerne, it was felt that an attempt should be made to ascertain to what extent different methods of grazing would affect the yield and stand of the crop, and with this object in view experiments were started at Grootfontein in 1925. No reports have yet been published as it was considered that the methods should first be given an extended trial.

It was impossible on the small plots (1/169 morgen) to graze the lucerne with sheep, but grazing was imitated by cutting the lucerne with a sickle as soon as the crop attained a height of about six inches. The short material so removed was dried and weighed, to obtain the yield from the grazed plots.

It may be contended that this method is not so hard on the crops as is actual grazing, but from the fact that the continuously grazed (i.e. cut) plots have now practically no lucerne left the stand consisting mainly of grass, it can be taken that the purpose, viz., to simulate grazing, has been served by the frequent close cuttings.

In the choice of treatments, we were guided by the fact that any system of grazing lucerne must allow for the provision of hay for use during the winter, unless, of course, some other crops such as winter cereals are to be grown for winter grazing. Consequently the treatments were mainly various alternations of grazed and hay crops with; in addition, some plots to facilitate study of the effect of seasonal grazing.

In the two Tables are given the average results of the six seasons, 1925-26 to 1930-31.

 

 

Table I shows that there is little difference between the yields of the two varieties Provence and Chinese. It will be noted, however, that Provence out-yielded the Chinese variety by two tons per morgen the continuously grazed plots. While there are still a fair number of lucerne plants left on the continuously grazed Provence plots, there are few left on the similarly treated Chinese beds.

Examination of the plots shows plainly that Chinese will not stand close and continuous grazing so well as will Provence, although this variety is no more seriously affected by the other methods of grazing than is Provence.

In Table II an attempt has been made to classify the grazing treatments into groups, each with equal numbers of hay and grazed crops. The yields of the ungrazed controls and the continuously grazed beds have been inserted in each column, for purposes of comparison.

It is quite clear that, as the proportion of hay crops to grazed crops decreased, there is a marked decrease in the yield. Thus with a proportion of two hay crops to one grazed crop we get an average yield of 18.2 tons per morgen, whereas with the proportion of one hay crop to two grazed crops the yield is only 16.6 tons per morgen or a reduction of about 10 per cent.

 

Further Points

The Table also brings out the following points: -

  1. Grazing lucerne during the period of the two summer crops gives better results than with either autumn or spring grazing.

  2. Spring grazing is markedly detrimental to the yield; this can be noticed in the low yields where one or both of the first two (or spring) crops is grazed, such as: two spring crops grazed, one crop grazed followed by one hay, two grazed crops alternately with one hay crop and autumn and spring grazing.

  3. The plots used for hay production alone out-yielded all other treatments, while the continuously grazed plots gave the lowest returns, these being respectively 20.7 and 12.9 tons per morgen.

From the data presented it is possible to make certain recommendations in regard to the grazing of lucerne, and these suggestions are substantiated by certain grazing experiments with sheep now being conducted at Grootfontein.

Grazing experiments with sheep on lucerne have been under way for a year, and other experiments are about to be started with dairy cows to obtain information on the carrying capacity, effect of grazing on lucerne and the conditions under which this crop may safely be grazed.

 

Proposals

The following proposals are offered:

  1. Lucerne should not be grazed during the growth of the first spring crop. If grazing is required, then a system should be devised to include winter cereals for spring grazing, or, alternatively, the first spring crop of the lucerne should reach the 10 percent bloom stage before being fed oft.

  2. Lucerne can be grazed without serious injury to the crop if hay crops alternate with grazed crops, but care should be taken to see that the first crop in the season is always cut for hay.

  3. Two hay crops followed by one grazed crop seems to be one of the least detrimental treatments and is recommended where hay is required during the winter for, say, both the sheep used on the grazing paddocks and for other stock. The saving in harvesting costs will no doubt make up for the reduction in yield obtained from plots alternately cut for hay and grazed.

  4. This system of alternate grazing will provide for the hay required in winter, when there is little or no grazing from the lucerne.

  5. Never, if possible, keep the lucerne lands moist and grazed short in the winter; this will result in the encroachment of grass, to the detriment of the lucerne.

  6. The crop should reach the 10 percent bloom stage before grazing. Do not commence grazing when the lucerne is still short.

  7. Graze off camps rapidly by using small paddocks or large numbers of animals in preference to larger camps and fewer stock. For example, if the lucerne takes 35 days to reach 10 percent bloom after being cut, have two sets of 5 camps in one of which the camps are each grazed down in rotation in about a week, while in the other the camps are cut for hay, so that the first camp will have 35 days growth before being cut for hay or being grazed, as the case may be. This is preferable from the point of view of effect on the lucerne to 3 camps on one of which the stock are grazed continuously for 35 days while the other two are allowed to grow to provide the next grazing and hay crops.

  8. A stand of lucerne younger than two years should only be grazed very lightly, if at all.

 

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