Pasture management influences runoff and soil movement in the semi-arid tropics

1995 ◽  
Vol 35 (1) ◽  
pp. 55 ◽  
Author(s):  
JG McIvor ◽  
J Williams ◽  
CJ Gardener
Keyword(s):  
Introduced Species ◽  
Suspended Sediment ◽  
Neutral Red ◽  
Stocking Rate ◽  
Pasture Management ◽  
Rainfall Events ◽  
Soil Movement ◽  
Low Level ◽  
Small Cover ◽  
Semi Arid

The influence of pasture management (sowing introduced species, timber treatment, clearing and cultivation, stocking rate) on runoff and soil movement was measured on a neutral red duplex soil at Cardigan, near Charters Towers. Runoff and soil movement were greatest in native woodlands and least in developed pastures, although the differences were often not significant. Runoff and soil movement were related to cover levels on the plots. In small rainfall events (total 4 0 mm and intensity e l 5 mm/h), runoff and soil movement decreased rapidly as cover increased, and only small cover levels (40%) were needed to reduce them to a low level. As the size of the storm increased, greater cover levels were required, and for very large events (total >100 mm and intensity >45 mm/h) cover had no effect on runoff although it still reduced soil movement. On neutral red duplex soils, managers should maintain at least 40% groundcover but this would still allow large losses of suspended sediment in large storms.

Addressing on-farm management to enhance pasture productivity and persistence

2013 ◽  
pp. 241-244
Author(s):  
W.N. Reynolds
Keyword(s):  
Management Strategies ◽  
Dairy Farm ◽  
Stocking Rate ◽  
Pasture Management ◽  
Pasture Production ◽  
Operating Profit ◽  
The North ◽  
The Cost ◽  
On Farm ◽  
Attention To Detail

Following the 2007/08 drought, we experienced poor pasture production and persistence on our dairy farm in north Waikato, leading to decreased milksolids production and a greater reliance on bought-in feed. It is estimated that the cost of this to our farming operation was about $1300 per hectare per year in lost operating profit. While climate and black beetle were factors, they did not explain everything, and other factors were also involved. In the last 3 years we have changed our management strategies to better withstand dry summers, the catalyst for which was becoming the DairyNZ Pasture Improvement Focus Farm for the north Waikato. The major changes we made were to reduce stocking rate, actively manage pastures in summer to reduce over-grazing, and pay more attention to detail in our pasture renewal programme. To date the result has been a reduced need for pasture renewal, a lift in whole farm performance and increased profitability. Keywords: Focus farm, over-grazing, pasture management, pasture persistence, profitability

Chlorinated Organics in Nearshore Waters and Tributaries of the St. Clair River

1986 ◽  
Vol 21 (3) ◽  
pp. 344-350 ◽  
Author(s):  
Barry G. Oliver ◽  
Klaus L.E. Kaiser
Keyword(s):  
United States ◽  
Suspended Sediment ◽  
Waste Disposal ◽  
Large Volume ◽  
Water Samples ◽  
Chemical Properties ◽  
Low Level ◽  
Chemical Company ◽  
Physical Chemical ◽  
The Individual

Abstract The concent rat ions of hexachloroethane (HCE), hexachlorobutadiene (HCBD), pentachlorobenzene (QCB), hexachlorobenzene (HCB) and octachlorostyrene (OCS) in large volume water samples show that the major sources of these chemicals to the St. Clair River are Dow Chemical Company effluents and, to a lesser degree, Sarnia’s Township ditch which drains one of Dow’s waste disposal sites. Tributaries entering the river on both sides of the Canada/United States border contain measurable concentrations of these chemicals indicating low level contamination throughout the area. The degree of water/suspended sediment partitioning of the chemicals (Kp) was studied. Kp values for the individual chemicals changed in a manner consistent with changes in their physical-chemical properties.

scholarly journals A robust low-level cloud and clutter discrimination method for ground-based millimeter-wavelength cloud radar

2020 ◽  
Author(s):  
Xiaoyu Hu ◽  
Jinming Ge ◽  
Jiajing Du ◽  
Qinghao Li ◽  
Jianping Huang ◽  
...  
Keyword(s):  
Hydrological Cycle ◽  
Spectral Width ◽  
Spatial Filter ◽  
Distribution Functions ◽  
Probability Of Detection ◽  
Climate Effect ◽  
Millimeter Wavelength ◽  
Low Level ◽  
Cloud Radar ◽  
Semi Arid

Abstract. Low-level clouds play a key role in the energy budget and hydrological cycle of the climate system. The long-term and accurate observation of low-level clouds is essential for understanding their climate effect and model constraints. Both ground-based and spaceborne millimeter-wavelength cloud radars can penetrate clouds but the detected low-level clouds are always contaminated by clutters, which needs to be removed. In this study, we develop an algorithm to accurately separate low-level clouds from clutters for ground-based cloud radar using multi-dimensional probability distribution functions along with the Bayesian method. The radar reflectivity, linear depolarization ratio, spectral width and their dependences on the time of the day, height and season are used as the discriminants. A low pass spatial filter is applied to the Bayesian undecided classification mask, considering the spatial correlation difference between clouds and clutters. The resulting feature mask shows a good agreement with lidar detection, which has a high probability of detection rate (98.45 %) and a low false alarm rate (0.37 %). This algorithm will be used to reliably detect low-level clouds at the Semi-Arid Climate and Environment Observatory of Lanzhou University (SACOL) site, to study their climate effect and the interaction with local abundant dust aerosol in semi-arid region.

scholarly journals Efficiency of pasture and supplement management in high producing dairy herds

2003 ◽  
pp. 105-110
Author(s):  
P.V. Salles ◽  
J. Hodgson ◽  
P.N.P. Matthews ◽  
C.W. Holmes ◽  
N.M. Shadbolt
Keyword(s):  
Dairy Farm ◽  
Farming Systems ◽  
Stocking Rate ◽  
Animal Performance ◽  
Pasture Management ◽  
Mean Values ◽  
Feeding Management ◽  
Dairy Systems ◽  
Supplementary Feed

In 1998 a three-year dairy farm monitoring programme funded by AGMARDT (Agricultural Marketing and Research Development Trust) was established on twelve dairy farms in the southern North Island of New Zealand where policy had changed from a focus on high production per ha through high stocking rate to a management based on reduced stocking rate and strategic use of supplements to enhance both production per cow and per ha. The project involved a detailed three-year data collection which included measurements of the quantity and composition of pasture and supplements consumed as well as animal performance. Analysis of the results of the third year (2000/2001) on nine of these farms with complete data sets identified a range of metabolisable energy (ME) intake (50669 - 70135 MJ ME/cow/yr). Supplementary feed represented on average 24% (21 - 27 %) of the total intake of ME, the main supplements being pasture silage (summer to winter), turnips (summer) and maize silage (autumn and winter) consumed by lactating cows, and grazing off by dry stock. There was a range of milksolids (MS) production per cow (372 - 424 kg/year) and per hectare (921 - 1264 kg/year). The average economic farm surplus per hectare of NZ$3077 (NZ$2425 - NZ$3867) for the case-study farms was approximately 43% higher than the top 25% farms in the Manawatu region. Mean values of return on assets for the case-study farms (12.9%) and top 25% farms in Manawatu (13.0%) were similar. Good pasture management based on controlled preand post-grazing herbage mass targets (mean 2650 and 1900 kg DM/ha, respectively), strategic use of supplementary feed to control pasture deficits, and moderate stocking rates (overall mean 2.7 cows/ha), provided high allowances of high quality herbage (organic matter digestibility ranging from 742 to 845 g/kg DM) and maintained high levels of milk production (411 kg MS/cow and 1100kg MS/ha). The comparison with industry data showed that the casestudy farms were highly productive and profitable dairy systems, at least under the conditions of the 2000/2001 season. However, the result indicated the need to improve management skills to limit feed wastage under generous feeding management, and also the limitation of conventional procedures for monitoring pasture consumption in farming systems. Keywords: animal performance, dairy systems, energy intak e, herbage quality, pasture management, profitability

scholarly journals Dairy farm systems to aid persistence

2011 ◽  
Vol 15 ◽  
pp. 199-209
Author(s):  
K.A. Macdonald ◽  
C. Matthew ◽  
C.B. Glassey ◽  
N. Mclean
Keyword(s):  
Insect Pests ◽  
Decision Rules ◽  
Dairy Farm ◽  
First Year ◽  
Stocking Rate ◽  
Pasture Management ◽  
Nitrogen Fertiliser ◽  
Feed Supplements ◽  
First Year Of Life ◽  
Introduced Weeds

This manuscript reviews fundamental pasture management principles relevant to pasture persistence. We first note some points of context, within which the debate on pasture persistence is occurring: the release of new pasture cultivars, the debate about climate change, and the effects of newly introduced weeds and pests. We then examine trends in farm practice. The critical management period (of most concern to farmers) has shifted from winter/autumn to summer. It is essential that farmers have and use sets of decision rules to govern when and how hard to graze, when to supplement and when to remove cows from pasture to allow pastures to be grazed appropriately to aid pasture persistence. Adaptations available to improve pasture persistence include: the use of nitrogen fertiliser to increase feed supply going into the summer, the use of crops or other feed supplements, stocking rate and on-off grazing to ensure the pastures are appropriately grazed in the summer. New pastures must be treated with care in their first year of life to ensure survival. The response of farmers to these variables to aid persistence of pastures is discussed. Keywords: climate, insect pests, pasture growth model, pasture renewal, weeds

scholarly journals Conceptual model of sedimentgraph from flood events in a small agricultural watershed

2008 ◽  
Vol 39 (1) ◽  
pp. 49-57 ◽  
Author(s):  
Kazimierz Banasik ◽  
J. Mitchell
Keyword(s):  
Conceptual Model ◽  
Suspended Sediment ◽  
Sediment Concentration ◽  
Agricultural Watershed ◽  
Sediment Flux ◽  
Flood Events ◽  
Rainfall Events ◽  
Sediment Routing ◽  
Suspended Sediment Flux ◽  
Lag Times

Conceptual model of sedimentgraph from flood events in a small agricultural watershed A procedure for predicting the sediment graph (i.e. the suspended sediment flux), from a small river catchment by heavy rainfall, has been developed using the concept of an instantaneous unit hydrograph (IUH) and dimensionless sediment concentration distribution (DSCD). A formula for instantaneous unit sedimentgraph (IUSG) is presented, and a procedure for estimating the sediment routing coefficient, which is a key parameter of the IUSG, based on measured data of rainfall-runoff-suspended sediment is applied. Field data from a small, field sized agricultural basin, lacated in center of Illinois has been used for analizing lag times for runoff (LAG) and sediment yield (LAGs). Assumptions about sediment generated during rainfall events are discussed.

scholarly journals Drivers of inter-annual variability in Net Ecosystem Exchange in a semi-arid savanna ecosystem, South Africa

2009 ◽  
Vol 6 (2) ◽  
pp. 251-266 ◽  
Author(s):  
S. A. Archibald ◽  
A. Kirton ◽  
M. R. van der Merwe ◽  
R. J. Scholes ◽  
C. A. Williams ◽  
...  
Keyword(s):  
South Africa ◽  
Eddy Covariance ◽  
Photosynthetically Active Radiation ◽  
Ecosystem Respiration ◽  
Net Ecosystem Exchange ◽  
Ann Model ◽  
Rainfall Events ◽  
Active Radiation ◽  
Annual Variability ◽  
Semi Arid

Abstract. Inter-annual variability in primary production and ecosystem respiration was explored using eddy-covariance data at a semi-arid savanna site in the Kruger Park, South Africa. New methods of extrapolating night-time respiration to the entire day and filling gaps in eddy-covariance data in semi-arid systems were developed. Net ecosystem exchange (NEE) in these systems occurs as pulses associated with rainfall events, a pattern not well-represented in current standard gap-filling procedures developed primarily for temperate flux sites. They furthermore do not take into account the decrease in respiration at high soil temperatures. An artificial neural network (ANN) model incorporating these features predicted measured fluxes accurately (MAE 0.42 gC/m2/day), and was able to represent the seasonal patterns of photosynthesis and respiration at the site. The amount of green leaf area (indexed using satellite-derived estimates of fractional interception of photosynthetically active radiation fAPAR), and the timing and magnitude of rainfall events, were the two most important predictors used in the ANN model. These drivers were also identified by multiple linear regressions (MLR), with strong interactive effects. The annual integral of the filled NEE data was found to range from −138 to +155 g C/m2/y over the 5 year eddy covariance measurement period. When applied to a 25 year time series of meteorological data, the ANN model predicts an annual mean NEE of 75(±105) g C/m2/y. The main correlates of this inter-annual variability were found to be variation in the amount of absorbed photosynthetically active radiation (APAR), length of the growing season, and number of days in the year when moisture was available in the soil.

Pasture management in semi-arid tropical woodlands: dynamics of perennial grasses

2007 ◽  
Vol 29 (1) ◽  
pp. 87 ◽  
Author(s):  
John G. McIvor
Keyword(s):  
Perennial Grasses ◽  
Individual Species ◽  
Stocking Rate ◽  
Pasture Management ◽  
Management Options ◽  
Exotic Grasses ◽  
Heteropogon Contortus ◽  
Basal Cover ◽  
Growing Seasons ◽  
North East

The effects of a range of pasture management options (introduced legumes and grasses, superphosphate, timber treatment, cultivation before sowing and stocking rate) on the basal cover of perennial grasses were measured from 1982 to 1991 at two sites, ‘Hillgrove’ and ‘Cardigan’, near Charters Towers, in north-east Queensland. Colonisation and survival of eight native and exotic grasses were followed in permanent quadrats in a subset of treatments. Overall, there were significant changes in total basal cover of plots between years and with tree killing, but no significant differences in sown pastures, fertiliser or stocking rate. Basal cover increased when defoliation levels were less than 40% but increases were smaller at higher levels of defoliation and basal cover often declined when defoliation was greater than 60%. Basal cover declined when growing seasons were <10 weeks, remained static with 10–15 weeks growth, and increased when growing seasons were 16 weeks or longer. There was some colonisation in all years but large differences between years. The differences in colonisation between systems were generally small but there was a general trend for higher colonisation at higher stocking rates. Bothriochloa ewartiana (Domin) C.E.Hubb. and Chrysopogon fallax S.T.Blake had low, Heteropogon contortus (L.) P.Beauv. ex Roem.&Schult., Cenchrus ciliaris L. and Aristida spp. had intermediate, and Bothriochloa pertusa (L.) A.Camus and Urochloa mosambicensis (Hack.) Dandy had high colonising ability. Survival of individual species was generally similar at both sites except for Urochloa mosambicensis. Heteropogon contortus and U. mosambicensis at ‘Hillgrove’ were short-lived (<10% survival after 4 years), B. ewartiana, Themeda triandra Forssk. and Aristida spp. had intermediate survival (10–50%), and C. ciliaris, C. fallax, B. pertusa and U. mosambicensis at ‘Cardigan’ were long-lived (>50% survival). Annual survival rates increased with plant age, were higher in good growing seasons than in poor seasons, were higher for large plants than small plants, and were lower at high defoliation levels than where defoliation was less severe. The differences between species in ability to colonise and survive, and the small influence of management compared to seasonal effects on survival, are discussed to explain species performance in pastures.

Distribution of Grass Species and Attributes of Grasses Near a Bore Drain in a Grazed Semi-arid Subtropical Grassland

1997 ◽  
Vol 45 (5) ◽  
pp. 919 ◽  
Author(s):  
R. W. Rogers ◽  
C. Stride
Keyword(s):  
Introduced Species ◽  
Carbon Assimilation ◽  
Distribution Patterns ◽  
Common Species ◽  
Grass Species ◽  
Semi Arid ◽  
Selection Of

The distribution of grass species and a selection of attributes of those species were related to distance from water in an otherwise natural, sheep-grazed, semi-arid, subtropical grassland at Glencoban Station near Cunnamulla in south-western Queensland, Australia. Twenty common species could be classified as decreaser, increaser or neutral with respect to stocking pressure based on distribution patterns with respect to distance from water. No species known to be introduced to Australia were present. The occurrence of a diversity of vegetative and diaspore attributes and carbon assimilation pathways were also shown to be related to stocking pressure. The attributes studied showed autocorrelation in two groups, which related to the higher level taxonomy of the grasses and to response to stocking. Chloridoid grasses increase and andropogonoid grasses decrease under high stocking pressure. In this grassland, which has no introduced species, a syndrome of stocking-related attributes can be discerned.

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