He studies the chemical composition of the herb to see if this can be linked to its feeding. In the area of the Union with summer precipitation, the cold winter month has almost completely ceased. On the other hand, if we take into account the deterioration of the nutritional properties of the plant during the dormant season and if it is
The use of part of the annual corn crop for this purpose has been repeatedly advocated. The possibilities of alfalfa in the drier parts of the winter rainfall area are also being investigated at that institute. The investigation to be reported in the following pages is an attempt to obtain information on several phases of the possibility mentioned.
Some of the earliest investigations into the chemical composition of South African nutrients were by Jm-it7. Samples of pasture were collected from human grazing areas in Britain and from some overseas territories of the Empire. Du 'J'oit et al (1935) found that cutting at monthly intervals can also sometimes be too drastic for the viability of the plants.
It is then clear that the most important factors influencing the chemical composition of pastures are plant species, the plants' growth stage, climatic conditions and.
Section A.-The Influence of Frequency of Cutting on the Yield and Chemical Com-
METEOROLOGICAL DATA
The main characteristics of the weather conditions for the period of the experiment are given in Table I. For comparison, the annual monthly rainfall from January to December for the last 25 years is included in the table. Later he will see that in the two seasons covering the experiment the plots are harvested in each case {or the last time in early April.
Consequently, the rainfall that could have influenced the composition and yield of the obtained herbs was that recorded for the period September to the end of March. By comparing the 1·ainval during the said period for the two seasons of the e:s:pe1·iment with the average, it is found that the total for hot seasons is above normal. On the other hand, a look at figure 1 which gives the distribution of the rainfall as monthly totals for the seasons of the experiment shows several deviations from the normal.
Until January, the 1935–36 season was abnormally dry, while the 1936–37 season was closer to normal conditions, apart from a dry spell in December. Heavy rain showers were experienced in early February and these were followed by intermittent dry and warm weather caused by light, ineffective showers. during the two seasons~.
TECHNIQUE
After the material was air dried, it was weighed and the figures thus obtained were used to compare its yield. However, no facilities were available in the experimental plots, so the only alternative was the air-dry material. It can be added that the material in the bags was turned over occasionally so that no "heating" of the grass occurred.
The flask with its contents was then carried to the laboratory a mile away and weighed. Crude protein, crude fiber, nn A separate e:xtTact was prepared for the determination of phosphorus niHl chlorinP nccorchng according to the directions given by Malan and Ynn der Lingeu (19Cl1). The essential difference between the methods of preparing the E:- hYo extracts consists in the addition of calcium acetate solution to the material before combustion in light of the phosphorus-chlorine extract. Follo,Ying are brief details of the principles by which the methods used are hasecl:-. INFLJEKCE OF CT.;TTJXG ON YIELDS ETC. OF GRASS TYPES. i) Phosphorus iethols by Bell anll Daisy (1920) and Deniges (1920), adapted for the determination of phosphorus in grasses by Malan and van der Lingen (1931). - Principle - Molybrate added to the test solution. -The calcium present is precipitated as oxalate and then the magnesium as magnesium ammonium phosphate, after which the phosphorus is determined calorimetrically. Principle - Potassium is precipitated under standardized conditions as potassium sodium cobaltinitrite, which is titrated with a solution of 0 · 01 N potassium pennanganate. A brown color is formed, the intensity of which is proportional to the amount of uranium present. vi) Chlorine. V olhard's method for the detection of halides was adapted by Malan and van der Lingen for the determination of chlorine in grasses. Principle chloride is precipitated as silver chloride by adding silver nitrate to the test solution and titrating the excess silver nitrate with potassium sulphocyanide. Thus, a comparison of the observed and theoretical values for z shows that Yarieties are significantly different, cuts are significantly different, and the interaction (Yariety x cuts) is significantly rliJfe1·eut, all at .P= ·01. It is therefore wise to move on to the t-test to discover where this meaning lies. v 25 The standard error of the difference between two. It can be concluded that, although there is no significant difference between the species Setaria and Panicum, both species yielded significantly more dry matter than the varieties Chl01·is, Digitaria and Cenchrus, while the odds of this were greater than 100:1. significant variation effect. The three latter varieties are insignificantly different. ii) Sign1: correlation between differences between sections. The standard error of a single sub-plot = 211· 0, and the standard error of the difference between the means of 25 sub-plots. Therefore, the statistically significant elements in the result can be summarized as follows: Cutting at 2, ~), 4 and (j monthl~· intPnab gives For the species DigitnTia and PaniC1llll Yariety, a 4-month rest period is significantly better than only one month of rest at P= ·01, and significantly better than 11th periods of 2 and 3 months. at P = · 05. In the case of Fanin1m Yariety, significantly more pure matter is obtained by allowing the herb to grow undisturbed for six months before harvesting than by cutting at monthly intervals. mme as 100 : 1 in favor of a six-month cutting rotation. Considerably more rhythm is produced by cutting at 6- and 4-monthly purposes than by cutting at 3- and 1-monthly intervals, and the 2-monthly c;ystem is decidedly superior to the monthly system for producing The yields of rl1 matter in a 2-month and 0-month cutting system are significantly different with respect to the former system. On the other hand, dry matter yield from cuttings at 2-, 4-, and six-month intervals is slightly different. Summarizing the main features in the results of t"·o Reasons of the experiment with reference to statistically significant elements<:ant, it is concluded that of the studied grass species Seta1·ia Linden-bergiana and flmu:cum ma In terms of cutting treatment, the most prominent feature is the reducing effect on dry matter yield in a system where grasses are cut at monthly intervals during the growing season compared to more gentle cutting systems. Of the milder <:utting treatments p1·oduced the 6- and 4-month systems overall more your substance than the 2- and 3-month systems. The inferior position occupied by the 3-month system in the 1936-37 season cannot he accepted as normal without further evidence, considering that a monthly cutting treatment, mentioned earlier in this report, had to be applied to enrl. of the previous season to suit the requirements of the experienced. Furthermore, the evidence from the results of species combined in the 1936-1937 season and from the results of individual species for the previous season suggests that the amount of clry material available with a bimonthly mowing system need not differ. significantly from that of one cut at the end of the season or two cuts, as represented by a four-month cut in February, followed by a cut two months later. In concluding these observations, it should be pointed out that the results obtained are probably valid only for the conditions of the soil and climate under which the grasses were grown.RESULTS
