Grass-clover Swards Research Articles

Studies on the cutting management of grass-clover swards:V. The effect of changes in the closeness of cutting at different times in the season on the yield and quality of herbage from a perennial rygrass-white clover sward

1. The effects of changing the closeness of cutting at different times in the season on the yields and quality of herbage were studied for 3 years on a perennial ryegrass-white clover sward.

The value of liquid digested sewage sludge. I. The effect of liquid sewage sludge on growth and composition of grass-clover swards in South-east England

During the period 1959-62 liquid digested sludge was applied to grass to supply nitrogen at rates similar to those normally recommended to farmers. The responses were compared to those produced by equivalent inorganic fertilizers.Liquid digested sludge gave as large an increase in dry matter as equivalent fertilizers. At the low rate of application the mean dry matter increase was 15.2 lb./lb. of applied nitrogen, and at the high rate the mean response was 11.0 lb. dry matter per lb. of nitrogen.On one site, all treatments reduced the clover percentage, the high rate more than the low rate. Sludge treatments reduced the clover percentages less than equivalent inorganic fertilizers.

Studies on the cutting management of grass-clover swards. IV. The effects of close and lax cutting on the yield of herbage from swards cut at different frequencies

1. The effects of cutting herbage to either 1 in. or 2½ in. from ground level were studied at varying cutting frequencies in two experiments on a perennial rye-grass/white-clover sward. In one of the experiments the frequency of cutting was decided by the stage of growth of the herbage, and in the other it was decided on a time basis where cutting was carried out at intervals of 2, 4 or 6 weeks throughout the growing season.2. Greater yields of herbage dry matter were obtained by cutting to 1 in. rather than to 2½ in. at all cutting frequencies in both experiments. This effect did not vary significantly with frequency of cutting where cutting dates were decided by the stage of growth of the herbage. However, where the cutting frequency was decided on a time basis, close cutting gave a relatively greater yield increase compared with lax cutting where the herbage was cut every 2 weeks instead of every 4 or 6 weeks.3. The results suggest that the practice of cutting at an average stage of growth in previous experiments probably had little or no influence on the effects recorded for the contrasting closeness of cutting treatments.

The effects of nitrogenous fertilizers on the winter growth of pastures in a tablelands environment

Second-year grass swards near Canberra, A.C.T., responded well in August and September to nitrogen (urea or ammonium sulphate) applied in June or July, with increases in yield of up to 17 lb of dry matter for each lb of nitrogen applied. Mixed grass-clover swards showed smaller responses in total dry matter after applications of urea in July, but applications of urea in April produced no significant response. In 1961, when the grass component of the mixed swards responded to urea applied in April, there was a concurrent clover suppression before the early September harvest, which eliminated any potential increase in total yield. Seasonal differences and the date of nitrogen application influenced the extent of August-September responses more than the particular grass species. The grasses differed greatly in their mean yields, irrespective of the nitrogen treatment, and also in their influence on the yield of the associated clover, but the response to nitrogen by the grass component was essentially similar for Wimmera ryegrass (Lolium rigidum Gaud.), Clunes perennial ryegrass (Lolium perenne L.), Phalaris (Phalaris tuberosa L.), and Demeter fescue (Festuca arundinacea Schreb.).

Studies on the cutting management of grass-clover swards. III. The effects of prolonged close and lax cutting on herbage yields and quality

1. The effects of two heights of cutting—down to either 1 in. or 2–2½ in. from ground level—on herbage yields were studied for five seasons with a perennial rye-grass-white clover mixture and for three seasons with a timothy-white clover mixture. Superimposed on these height-of-cutting treatments were treatments simulating strip grazing with and without a back-fence, and also three fertilizer nitrogen treatments.2. Over the 5-year period the rye-grass mixture consistently gave greater dry-matter and crude-protein yields of herbage when cut to 1 in. than it did when cut to 2–2½ in. from ground level, the mean dry-matter yield difference being 34%. The decline in the total yield per season with increasing age of the grass sward was similar under both heights of cutting.3. The effects of the height-of-cutting treatments on the timothy mixture were similar to those noted on the rye-grass mixture in the first three seasons of the experiment, but in the third year the beneficial effects of close cutting were much reduced. It is suggested that this resulted from the rest period between cuts being insufficient for timothy to recover fully from the close defoliation.4. The effects of the height-of-cutting treatments on the botanical composition of the sward were slight, particularly on plots of the rye-grass mixture.5. Possible factors leading to the observed effects of the height-of-cutting treatments are discussed with reference to the results of other workers and to the results from a preliminary study of the differential effects of the treatments on stem and leaf formation in perennial rye-grass.6. A simulation of strip grazing with and without a back-fence showed that the herbage yields from both seeds mixtures under both height-of-cutting treatments were considerably reduced by the removal of the regrowth which could take place in the absence of a back-fence.7. The effects of delaying the first nitrogenoua fertilizer application of the season noted in an earlier experiment were fully confirmed in this experiment.

Light relationships in grass-clover swards

Grass-clover swards were grown at four levels of nitrogen to provide a range from extreme clover dominance to extreme grass dominance. Yield, botanical composition, leaf area index, and light density were measured at 3.5 cm vertical intervals in each of the mixed swards throughout the growth period. It was directly demonstrated that the growth of clover in these mixed swards was governed by a series of relationships, namely: (a) Increasing rates of nitrogen application gave increased yields of grass (positive). (b) Increased yields of grass gave higher leaf areas of grass disposed above the clover leaf canopy (positive). (c) Higher leaf areas of grass above the clover reduced the light density at the clover leaf canopy (negative). (d) Reduced light density at the clover leaf canopy caused a reduced growth of the clover (positive). Under conditions of heavy grass growth and of consequent low light density at the clover canopy, the growth of clover not only became slow but eventually was strongly negative, leading to a marked reduction in both the number of clover plants and the yield of clover.

Factors influencing the role of clover in grass-clover leys fertilized with nitrogen at different rates III. The effects of the variety of companion grass and of the variety of clover on the botanical composition of the sward

1. In an experiment designed to study some of the factors influencing the role of clover in grassclover swards fertilized with nitrogen at different rates, botanical studies of the sward were made each spring and autumn. The methods used, and the results obtained in the autumn studies, are described in this paper.2. Full details of the experimental treatments and design, and the yield results have been reported previously.3. The botanical composition of the sward depended to a far greater extent on the variety of grass than it did on the variety of clover included in the seeds mixture. This was true also of the yields from the different swards.4. Some relationships are suggested between the yield and nitrogen response results and the variations in the botanical composition of the sward attributable to the variety of grass included in the seeds mixture.5. Kersey white clover appeared to be more persistent than S. 184 and S. 100 where fertilizer nitrogen was applied to the sward, although no differences in persistency were noted in the absence of applied nitrogen.6. A statistical study of the botanical data obtained indicated that the intensity of sampling employed gave the optimum balance between variance and time expenditure, since only a slight reduction in variance would have been obtained if double the number of samples had been taken.

Factors influencing the role of clover in grass-clover leys fertilized with nitrogen at different rates II. The effects of the variety of white clover on the yields of total herbage and of clover

1. A brief description is given of an experiment in which some of the factors influencing the role of clover in grass—clover swards fertilized with nitrogen at different rates were studied.2. Reference is made to a previous paper detailing the experimental methods and reporting the results pertaining to the effects of the grass varieties included in the seeds mixture on the yields of mixed herbage and of clover. The effects of the clover varieties on these yields are discussed in the present paper.

Factors influencing the role of clover in grass-clover leys fertilized with nitrogen at different rates I. The effects of the variety of companion grass on the yields of total herbage and of clover

1. A study has been made of some of the factors influencing the role of clover in grass-clover swards fertilized with nitrogen at different rates.2. From 1955 to 1957 inclusive three nitrogen treatments, 0, 4 and 10 cwt. ‘Nitro-Chalk’ (15·5% N)/acre/season, were applied to twentyone grass-clover mixtures sown in the spring of 1954. The mixtures contained either S 184, S100 or Kersey white clover alone or in association with one of the following grasses, S 23 or S 24 perennial ryegrass, S143 or S37 cocksfoot, S48 timothy or S53 meadow fescue.

SOME EFFECTS OF FERTILIZATION ON THE YIELD, BOTANICAL AND CHEMICAL COMPOSITION OF IRRIGATED GRASS AND GRASS-CLOVER PASTURE SWARDS

In an irrigated pasture experiment on Vancouver Island, on a soil deficient in available nitrogen and potassium but apparently containing sufficient available phosphorus, calcium and magnesium for adequate plant growth, an irrigated Ladino clover-grass mixture greatly outproduced a grass mixture on a forage, protein and mineral nutrient yield basis. In order to attain even a moderate yield with a grass mixture, heavy fertilization with nitrogen and potassium was necessary. Nitrogen fertilization was not essential to high yields with the Ladino clover-grass mixture. Nitrogen fertilization tended to decrease the per cent Ladino clover and the protein and calcium content in the clover-grass forage and increased the protein content of the grass herbage. The calcium content of the grass herbage was decreased by nitrogen fertilization. The phosphorus and magnesium contents of the clover-grass and grass herbage were not appreciably altered by nitrogen fertilization. Decreasing the time interval between nitrogen applications resulted in a more even production of dry matter over the growing season but did not increase the total seasonal yield. Potassium fertilization increased the yield of both mixtures and increased the per cent clover in the grass-clover sward. Multi-annual potassium applications were required for the elimination of plant potassium deficiency symptoms and the applied potassium was quickly absorbed by the plants. Grass herbage contained more potassium, slightly more phosphorus and less calcium, magnesium and nitrogen than grass-clover herbage.

Studies on the cutting management of grass-clover swards Part II. The effects of close cutting with either a gang mower or a reciprocating-knife mower on the yields from an established grass-clover sward

1. In an experiment conducted on an established perennial rye-grass/white clover sward close cutting was carried out over a 3-year period (1956–58), either with a lawn mower to simulate gang mowing or with a reciprocating-knife mower. The sward was cut either six or eight times in each season, and received 0 or 2 cwt. ‘Nitro-Chalk’/acre for each cut.2. Swards cut with the gang mower yielded from 3·5 to 12·5% more herbage dry matter than swards cut with the reciprocating-knife mower and also gave a greater mean yield of crude protein.3. The difference in dry-matter yield between swards cut with each of the mowers is attributed to the slightly closer cutting level of the gang mower having a greater inhibiting effect on flower development in the grasses and hence stimulating leaf production and increasing total yields.4. In the second and third years of the experiment swards cut with the gang mower outyielded those cut with the reciprocating-knife mower by a proportionately greater amount when eight cuts rather than six cuts were taken in the season.5. When no nitrogenous fertilizer was applied the proportion of broad-leaved weeds in the sward increased more rapidly over the 3-year period where the herbage was cut with the gang mower rather than the reciprocating-knife mower. This disadvantage of gang mowing did not apply where the fertility was maintained at a high level by applications of nitrogenous fertilizer.6. It is concluded that the gang mower is a more suitable machine than the reciprocating-knife mower for close cutting on a field scale.

Studies on the cutting management of grass-clover swards. I. The effect of varying the closeness of cutting on the yields from an established grass-clover sward

1. A 3-year experiment is described in which perennial rye-grass/white clover swards were cut to within either 1 in. of 2–2½ in. of ground level when the herbage had reached either the ‘grazing’ or the ‘silage’ stage of growth. Superimposed on the cutting treatments were several fertilizer treatments which involved application of varying amounts of nitrogen at different dates over the season.2. Throughout the experiment cutting to within 1 in. of ground level gave greater dry-matter and crude-protein yields of mixed herbage and of clover than cutting to within 2–2½ in. of ground level, the increase in dry-matter yield ranging from 39 to 49%.3. The response of clover to these ‘height of cutting’ treatments developed more slowly than the response of the sward as a whole, and was modified in the later stages by the particular fertilizer nitrogen treatment applied.4. It is suggested that the greater herbage yields obtained from close- than from lax-cut swards resulted from the differential effects of the two cutting treatments on stem and leaf formation in the grasses, but the need for further investigation is stressed.5. Discrepancies between the effects of the ‘height of cutting’ treatments in this experiment and those reported by other workers are indicated, and it is shown that these discrepancies probably result from the varying cutting frequencies adopted.6. Cutting the sward at varying stages of growth and increasing the rate of fertilizer nitrogen application had very similar effects on mixed herbage and clover yields in this experiment to those reported previously by other workers.7. Where the total amount of fertilizer nitrogen applied over the season was small (4 cwt. ‘Nitro-Chalk’/acre) delaying the first dressing until after the first or second cut reduced the dry-matter and crude-protein yields of mixed herbage, and had little effect on those of clover. A similar delay where greater total amounts of fertilizer nitrogen were used (8–12 cwt. ‘Nitro-Chalk’/acre) reduced the dry-matter yields of mixed herbage, and slightly increased the dry-matter and crude-protein yields of clover. Under these heavy nitrogen treatments the crude-protein yields of mixed herbage decreased only where the delay involved a reduction in the total amount of fertilizer nitrogen applied over the season.8. Although delaying the first dressing of the season reduced mixed herbage yields at all fertilizer nitrogen levels, it resulted in a more uniform distribution of production over the season. The practical significance of this is discussed.

Irrigation of grassland

Field experiments are described comparing the yield of herbage on a series of grass-clover plots which were irrigated after various deficits had developed. In addition to the irrigation treatments, different rates of nitrogen were applied.The maximum yields were obtained when only small deficits were allowed (maximum pF 3·3). This applied particularly to grass-clover swards to which no nitrogen fertilizer was applied.There was not much reduction in yield on predominantly perennial ryegrass swards liberally supplied with nitrogen when larger deficits were allowed to develop (pF c. 4·0).Estimates of soil water deficit from meteorological data using Penman's method agreed very well with direct measurements.

Nitrogenous manuring of grass-clover leys for conservation, with particular reference to ‘late’ top-dressing

Results are recorded of experiments over four years to study the effects of various rates of N fertilizer applied early (soon after each cut) and late (1 or 2 weeks before cutting) to grass-clover swards cut repeatedly for conservation.N fertilizer proved essential for high yields of dry matter and protein per acre. It reduced the amount of clover, but it is clear that clovers are not as productive as grasses adequately manured, and that any N excreted by clovers into the soil is far from enough to enable associated grasses to make full growth.The amount of N fertilizer applied proved more important than the time of its application. Early N gave higher yields of dry matter but rather lower percentages of crude protein in the herbage than late N dressings.To increase yields substantially and at the same time to maintain the protein content of the herbage on a par with a grass-clover ley it seems necessary to apply a minimum of 4 cwt. ‘Nitro -Chalk’/acre as an early dressing before each cut. An additional 2 or 3 cwt. ‘Nitro-Chalk’/acre may be applied from one to two weeks before cutting if even higher crude protein values are required.