Sward Quality Research Articles

Herbage and animal production responses to fertilizer nitrogen in perennial ryegrass swards. I. Continuous grazing and cutting

The effects of fertilizer N application on herbage intake and animal performance under continuous grazing management with dairy cows, and on herbage accumulation under a weekly and an approximately 4-weekly cutting regime were studied in 1986-1988 in resown Lolium perenne cv. Wendy grassland on a silty loam soil in Oostelijk Flevoland, Netherlands. 250-700 kg N/ha was applied annually under grazing and from 0 to 700 kg N/ha was applied under cutting. At an assumed marginal profitability of 7.5 kVEM per kg N applied the optimum N application rate was on average 511 and 308 kg/ha per year for 4-weekly cutting and continuous grazing, respectively (1 kVEM = 6.9 MJ Net Energy for lactation). However, especially under grazing, there was a great variation in response to N between years which could be related to soil N availability, length of the growing season and sward quality. Throughout the experimental period the mean tiller density in the grazed swards was hardly affected by the level of N application. However, there were temporary differences in openness of the sward which increased with the level of N application, leading to a loss of productivity as a result of impeded N uptake. Herbage N was poorly converted into animal products. The average efficiency of use of ingested N at 250 kg N was 23%. Higher rates of fertilizer N decreased N use efficiency (19% at 700 kg N/ha per year) but markedly increased N excreted per ha.

Sward characteristics and animal performance in a leader/follower grazing system with cows and sheep

The recommended post grazing stubble height for dairy cows in a rotational grazing system in spring is 8 to 10 cm. However, this height leads to much stem elongation and reduction in sward quality in mid and late season. Consequently, pastures require topping in June/July to maintain grass quality and reduce sward deterioration, particularly in rejected areas around dung pats. O'Riordan (1989) suggested that a leader/follower rotational grazing system with ewes following dairy cows could improve pasture utilisation and eliminate the need for topping. This was confirmed by Swift et al. (1991) who also demonstrated that grazing at one ewe with twin lambs per cow improved the utilisation of grass and allowed for acceptable ewe and lamb performance without apparently decreasing cow grazing days or milk output.The objective of this work was to examine the effects of leader/follower rotational grazing with dairy cows and lambed ewes on grass tillering in a cool, wet western environment.

A field method for the determination of total nitrogen in plant tissue

Abstract While studying sward quality in Kenya, East Africa, we established a field laboratory for the determination of total nitrogen. Using Kjeldahl digestion procedures and an indophenol colorimetric method, we successfully analyzed over 900 plant and fecal samples while living in a tent camp. Variation from one digestion to the next was corrected for by using a grass standard with each digestion. Independent tests by other laboratories verified the accuracy of our methods.

The relationship between sward structure, ingestive behaviour and dietary quality in cattle grazing a Chloris gayana pasture

The relationship between sward structure, ingestive behaviour (bite size, biting rate and intake rate) and dietary crude protein (CP) content was studied on a Chloris gayana pasture at different growth stages using oesopha‐geally‐fistulated steers. As the pasture matured, leaf table height, plant height, disc height, stemminess and standing herbage increased while leaf density and leaf percentage (%) declined. In conjunction with these changes, biting rate and dietary CP declined sharply, while bite size increased. Intake rate remained relatively constant for all sward structures. Animals adjusted biting rates to compensate for changes in bite size and thus maintained rates of intake. Bite size and dietary CP were negatively correlated. It was argued that, in the present study, leaf table height, stemminess, leaf density and leaf % were the main determinants of dietary CP and ingestive behaviour.

Evaluation of the use of a small leaved clover as an alternative to fertiliser-N on tetraploid and diploid perennial ryegrass swards grazed to controlled sward heights by ewes and lambs

Lamb performance at grass falls in July/August on upland farms. Allowing sward height to rise has been recognised as having an ameliorating effect [Keeling, 1987). The objective of this trial was to determine the influence of both sward quantity (sward height) and sward quality [sward type) on ewe and lamb performance from mid April to September. A further objective was the evaluation of clover as an alternative to nitrogen fertiliser.Three contrasting perennial ryegrass based swards were established in May 1987 for use in 1988 and 1989: a late heading diploid variety (D). CONTENDER and a late heading tetraploid variety [T) CONDESA sown alone or with S184 small leaved white clover [TO]. [D] swards represent the control being the normal upland pasture type. [T] companion ryegrass varieties have higher palatability and intake characteristics and, producing fewer tillers, are a compatible companion grass to white clover. Small leaved white clover was used owing to its higher persistency and dry matter production under continuous sheep grazing.

THE EFFECT OF ETHEPHON ON ANNUAL BLUEGRASS AND CREEPING BENTGRASS GROWTH

Under pot culture and field conditions, ethephon at rates up to 8 kg ha−1 was more injurious to annual bluegrass than to Penncross creeping bentgrass. Ethephon significantly decreased the quality, spreading ability and shoot weight of annual bluegrass, whereas sward quality of the creeping bentgrass grown in pot culture was increased, spreading ability was unaffected and shoot dry weight decreased. Increasing the number of applications at all concentrations increased injury to annual bluegrass and a single application at 1 kg ha−1 reduced annual bluegrass seedhead production.Key words: Poa annua, Agrostis palustris, ethephon, sward quality

Ewe and lamb performance on perennial ryegrass and perennial ryegrass plus white clover swards under controlled sward heights

Lamb performance at grass falls in July/August on upland farms. Allowing sward height to rise has been recognised as having an amoreilating effect. The objective of this trial was to determine the influence of both sward quantity (sward height) and sward quality (sward type) on ewe and lamb performance from mid April to September. An associated objective was the evaluation of the use of clover to replace nitrogen fertiliser.

Control of sward conditions and apparent utilization of energy in the buffer grazing system

AbstractExperiments were carried out over four years to develop a system of buffer grazing. Groups of 16 cattle were set stocked with or without buffer areas formed by withholding a proportion of the grazing area by electric fence. It was found that buffers should be grazed if sward height, measured by rising plate meter, was reduced below 5 cm, or otherwise cut for silage. Increasing the area of the buffer reduced cattle gains but increased silage yield and sward quality, and the best compromise over 4 years was a buffer area of 25‐30% of the initial grazing area. Buffer treatments gave higher UME and financial output than controls, due to the value of silage from the buffers and to the higher nitrogen inputs which were successfully managed under buffer grazing. The higher outputs over 4 years were also associated with lower viability and therefore lower levels of risk, resulting from a number of compensating processes at sward and animal level. There was no indication that grazed UME was higher on buffer treatments at a given level of nitrogen, suggesting that any increased grazing efficiency must be offset by other disadvantages when comparing intensive with lax defoliation regimes. The results suggest that there is considerable stability in grazing systems which may frustrate attempts to improve their biological efficiency, although there is some scope for manipulating the seasonal pattern of land use and animal performance.

The Influence of Species Diversity on Sward Yield and Quality

SUMMARY (1) An investigation of the yield and population structure of contrasting types of sward is described. The objective was to compare the quantity of herbage under cutting from swards consisting of species which had been bred for high yield, with that from swards which contained these species together with several indigenous grasses. (2) The swards were obtained by sowing one or more of the following seven herbage species: Agrostis stolonifera L., A. tennis Sibth., Festuca rubra L., Holcus lanatus L., Lolium perenne L., Poa pratensis L. and Trifolium repens L. The populations consisted of a mixture of Lolium and Trifolium, and complex mixtures containing all seven species. The latter were sown by broadcasting to give a random distribution of species, or in three alternative mosaic configurations of discrete colonies. Mosaics were used in order to reduce interspecific competition during establishment. The resulting swards received two levels of fertilizer nitrogen (and associated phosphorus and potassium) and were cut five times per year for 5 years. (3) At the lower level of nitrogen (50 kg N ha-1 year-'), the Lolium-Trifolium swards gave up to a 15% higher dry matter yield, and higher contents and yields of digestible organic matter and nitrogen than the complex mixtures. (4) At the higher nitrogen level (300 kg N ha-1 year-'), Lolium-Trifolium did not have an advantage over the complex mixtures in the yield of dry matter, digestible organic matter or nitrogen. (5) The results indicate that the presence of indigenous grasses does not inevitably reduce productivity below that of swards consisting entirely of improved species. Thus it may not always be necessary to renovate swards containing indigenous species in order to maximize production in the farm situation.

Limits to nitrogen fertilizer on grassland.

The effect of N fertilizer on seasonal response of predominantly Lolium perenne grassland, sward quality and productivity, herbage nitrate content and soil mineral N was studied in cutting trials lasting 1-6 years. At an assumed marginal profitability of 7.5 kg DM/kg N applied, the av. opt. annual N application on sand and clay soils was 420 kg/ha. At this rate, herbage nitrate content did not exceed 0.75% NO3 and accumulation of soil mineral N was minimal. At annual N rates exceeding 500 kg/ha sward quality deteriorated and productivity decreased the following year. (Abstract retrieved from CAB Abstracts by CABI’s permission)

Grassland productivity as affected by intensity of nitrogen fertilization in preceding years.

2 sown grasslands on a sandy and clay soil and an old permanent grassland on a clay soil comprising mostly perennial ryegrass were given up to 1120 kg N/ha annually and cut at various stages of development. Productivity decreased with increasing N application in the pretreatment yr, and was accompanied by a decrease in pasture quality. Annual applications of 400-480 kg N/ha gave a good balance between DM yield and sward quality. These results indicated that 1-yr field trials do not allow general conclusions as to long-term effects. (Abstract retrieved from CAB Abstracts by CABI’s permission)

Nitrogen accumulation in Kaolin wastes in Cornwall

Nitrogen accumulation and nitrogen mineralisation rates were measured in a series of waste heaps, produced by the china clay mining industry, which had been reclaimed at different times with a sward ofAgrostis tenuis, Festuca rubra, andTrifolium repens. The best swards tended to have high ammonification rates and rapid N turnover (which is represented by a nitrogen turnover index) —nitrification rates or nitrogen accumulation were not such good predictors of sward quality. Ammonification increased with pH and with organic nitrogen accumulation whereas N turnover was not related to these factors. Nitrification levels were generally low and it was concluded that nitrification was not important to sward health.

Effect of pre-grazing herbage mass and daily herbage allowance on perennial ryegrass swards structure, pasture dry matter intake and milk performance of Holstein-Friesian dairy cows

To maximize milk output and milk solids per hectare from grazing dairy cows it is necessary to identify the level of grazing swards in order to achieve high pasture dry matter intake (PDMI). The aim of this study was to investigate the effect of pre-grazing herbage mass (HM) and daily herbage allowance (DHA) on perennial ryegrass (Lolium perenne L.) swards structure, PDMI and milk performance. Sixty-four spring-calving Holstein-Friesian dairy cows were balanced and randomly assigned to one of four (n = 16) grazing groups (LL, LH, HL and HH) in a 2 × 2 factorial design. The treatments consisted on two pre-grazing HM, low (L- 1,600 kg DM ha–1) or high (H- 2,400 kg DM ha–1) and two DHA, low (L- 15 kg DM cow–1day–1) or high (H- 20 kg DM cow–1 day–1). Swards structure, PDMI and milk performance were examined across the grazing season. The low HM groups completed 9.5 rotations of average 22 days length compared to 6.5 rotations of 32 days for the high HM groups. Herbage utilization was greater (p < 0.001) when animals offered the low DHA (98.0%) compared to the high DHA (89.9%). Stem and dead DM yield (> 4.0 cm) were lower (p < 0.001) for the low HM (221 and 170 kg ha–1, respectively) than for the high HM (388 and 303 kg ha–1, respectively). The high DHA had higher (p < 0.001) milk output (19.5 kg day–1) and milk solids (1.46 kg cow–1). The highest milk output per ha and per cow was achieved by LH, with low post-grazing residuals and high sward quality.