Measurements were made of germinable seed of all species in the top 5 cm of soil beneath 9 paddocks in an 11-year-old pasture experiment in south-east Queensland. The experiment comprised two pasture types grazed by cattle: legume-grass (Macroptilium atropurpureum- Setaria sphacelata) pastures grazed at four stocking rates and nitrogen fertilized S. sphacelata pastures grazed at five stocking rates. Levels of germinable seed in the soil varied with pasture type and stocking rate and ranged from 6760 to 45480 seeds/m2. Seed reserves increased on the legume-grass pastures as stocking rate increased. Fifty-seven different plant species were identified from the seedlings grown from the soil seed reserve. For 11 of these species, which contributed 70% of the seed reserves, there were significant trends in relation to pasture type and/or stocking rate. The only species where seed reserves significantly decreased with increasing stocking rate were the two sown species. Cattle faeces were also collected from lightly and heavily stocked legume-grass and nitrogen-fertilized pastures in spring, summer, autumn and winter. Germinable seed contents of all species were measured. Seed content of faeces was higher in the summer and autumn than in the winter and spring samplings, and in the heavily stocked than in the lightly stocked pastures. The highest content recorded was 20.5 germinable seeds g-1 faecal dry matter. The species with the highest germinable seed content in faeces were Digitaria didactyla, Axonopus affinis and Eleusine indica, the latter being restricted to nitrogen-fertilized pastures. Seed dissemination in faeces is a factor contributing to the invasiveness of prostrate perennial grasses such as D. didactyla and A. affinis under heavy grazing.
Measurements were made of the seed set, seed content in cattle faeces, soil seed reserves, seedling regeneration and seedling survival of Siratro (Macroptilurn atropurpureum) in south-east Queensland. Measurements were made from 1972 to 1985 in pastures of Siratro/setaria (Setaria sphacelata) sown in 1968 and stocked at 1.1, 1.7 and 2.3 and at 3.0 (1969-1973) reduced to 2.0 (1974-1985) heifers ha-1. Siratro seed set and seedling demography were markedly affected by stocking rate. At the highest stocking rate, Siratro yields were low and seed input ceased after 1972, yet appreciable seedling recruitment from the soil seed bank was maintained for a further 10 years. At the lightest stocking rate (1.1 heifers ha-1), seed set and soil seed reserves were highest, but seedling recruitment was of little importance as almost all seedlings died. Seedling recruitment and survival were best at an intermediate stocking rate (1.7 heifers ha-1), where they were the key to long-term persistence of Siratro. Soil seed reserves of Siratro ranged from 500 m-2 under light stocking to < 100 m-2 after several years of heavy stocking. Very little seed was recovered in cattle faeces. Likely factors responsible for seedling death (light, water, nutrients, grazing, frosting and insect damage) are discussed. The limitations of seed set and seedling regeneration in the persistence of Siratro are contrasted with some other perennial pasture legumes. Studies of this type can help in qualitatively predicting long-term persistence of pasture legumes under different conditions of management and climate.
The persistence of plants and stolons of the tropical forage legume Siratro (Macroptilium utropurpureurn) was measured in Siratro-setaria (Seluriu sphacelala) pastures at Samford, south-east Queensland. The pastures were sown in 1968. Three pastures were set stocked and continuously grazed from 1969 to 1985 at 1.1, 1.7, and 2.3 heifers ha-1. A fourth pasture was stocked at 3.0 heifers ha-1 from 1969 to 1973 and at 2.0 heifers ha-1 thereafter. In 1972 the density of Siratro crowns was similar in the four pastures, although crowns were smaller and stolon density was considerably less at the highest stocking rate. Persistence of plants at a moderate stocking rate (1.7 heifers ha-1) and a heavy stocking rate (3.0/2.0 heifers ha-1) was followed in fixed quadrats from 1971 to 1986. Stocking rate had a marked effect on the recruitment of new crowns and on crown survival. Total numbers gradually declined at the heavy stocking rate and no plants were recorded after 1982. This decline was associated with poor survival of plants (half life of only 6 months) and with reduced input of new plants, particularly after 1980. In contrast, Siratro density at 1.7 heifers ha-1 remained constant from 1971 to 1978. and then increased to 1982. This was associated with a longer half life of plants (c. 20 months) and sustained input of new crowns. However, there was a drastic decline in Siratro density from 1982 to 1985. Siratro was clearly unable to persist under heavy grazing, but there was no single reason why it suddenly declined in a moderately grazed pasture where it had persisted for 14 years. However, the advent of Siratro rust, together with a run of years with below average summer rainfall, are likely major contributory factors. Both these factors increased the grazing pressure on Siratro under the set-stocking and continuous grazing that was imposed.
Relationships between readings of the electronic (capacitance) pasture meter and descriptions of pasture yield were examined over the yearly growth cycle in grazed pastures of Setaria anceps cv. Nandi, with or without Macroptilium atropurpurem cv. Siratro and Desmodium intortum cv. Greenleaf. There was a poor relationship between meter reading and pasture dry matter yield (r = +0-574 pooled over pastures and seasons) but this relationship was improved to r = +0-750 by inclusion of other regressors describing pasture height and proportion of inert material. Meter reading was more closely related to fresh pasture yield (r = +0-830), water yield (r = +0-885) or dried green yield (r = +0-830), although inclusion of a pasture height term still improved the relationship slightly. Suggestions are made about using the meter to estimate dried green yield rather than total dry matter yield, and taking more consideration of the proportion of inert material when relating the meter reading to total dry matter yield.Visual estimation was also compared with actual pasture yield measured by cutting. Even though prior training for yield estimation was inadequate, the relationships between visually estimated and actual yield were as good as those from the pasture meter. It is concluded that the pasture meter will not find a regular use as a sampling tool in most grazed tropical pastures.
Stolon length per unit area is a useful measurement to make in studies of white clover, but is time consuming and seldom done in routine sampling of grazing experiments. This study explored the possibility of using a calibrated visual estimation technique to estimate stolon length per unit area in a grazed pasture in south-east Queensland, Australia. Estimates were made of stolon presence in 50 quadrats on a 1-5 scale on 4 different occasions. These were converted to stolon length per unit area using a set of 10 standard quadrats which were estimated and then measured. The estimates on the 50 quadrats were then compared with their true values. Estimates of stolon length were very close to measured values and gave useful insight into seasonal changes in stolon length that were not detected by measurements of stolon presence/absence (% frequency). The procedure outlined could be readily incorporated with routine measurements of presentation yield and botanical composition made with the BOTANAL procedure.A 00006
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.