Accurate cover estimates in turfgrass research plots are often difficult to obtain because of the time involved with traditional sampling and evaluation techniques. Subjective ratings are commonly used to estimate turfgrass cover, but the data can be quite variable and difficult to reproduce. New technologies and software related to digital image analysis (DIA) may provide an alternative method to measure turfgrass parameters more accurately and efficiently than current techniques. A series of studies was conducted to determine the applicability of DIA for turfgrass cover estimates. In the first study, plots containing a range (1-16) of bermudagrass [Cynodon dactylon (L.) Pers.] plugs of specific diameter (15.0 cm) were established to represent values of turfgrass cover from 0.75 to 12%, by 0.75% increments. Digital images (1280 by 960 pixels) were taken with a digital camera and processed for percent green color to a software package. Estimates of green turfgrass cover by DIA were highly correlated (r 2 > 0.99) to the calculated values of turfgrass cover. In a second study, DIA of turfgrass cover was compared by subjective analysis (SA) and line-intersect analysis (LIA) methods for estimating cover in eight plots of zoysiagrass (Zoysia japonica Steudel). The mean variance of percent cover determined by DIA (0.65) was significantly lower than SA (99.12) or LIA (13.18). Digital image analysis proved to be an effective means of determining turfgrass cover, producing both accurate and reproducible data. In addition, the technique effectively removes the inherent error and evaluator bias commonly associated with subjective ratings.

Quantifying Turfgrass Cover Using Digital Image Analysis

Investigations on soil compaction focused mainly on effects on soil physical parameters and on plant growth. Nevertheless, a substantial number of papers deal with effects of soil compaction on soil organisms (soil fauna, soil microorganisms) and biologically driven processes in soils (e.g., macropore formation, respiration rates, N-mineralisation). In view of soil and soil functions protection, there is an essential need to identify soil compaction threshold values with respect to soil biota and soil biological processes. No such values are currently available. Thus the aim of our study was to evaluate literature on the effects of soil compaction mainly in agricultural soils on soil organisms and soil biological processes (e.g., respiration, nitrification); to identify relevant parameters which are helpful for assessing soil compaction from the soil biological point of view; and to find out whether threshold values of soil structure parameters proposed by soil physicists correspond to harmful impacts on soil organisms and biological processes in soils. Our literature review showed that due to the high variability of experimental situations and conditions in the evaluated papers, especially in papers describing field investigations, no general effect of soil compaction was found. Negative and positive effects occurred with slight compaction as well as with strong compaction. A verification of the thresholds published to date for soil compaction was not possible based on the data evaluated. However, the fact that above an effective bulk density of 1.7 g cm−3, only negative effects on microbial biomass and C-mineralisation were found confirms this value, proposed by soil physicists, also from the soil biological point of view. In order to provide a scientifically meaningful data base for the assessment of soil compaction, effects on soil biodiversity, related functions and processes, we recommend considering the following site and soil properties as essentials: land use, climate, soil type, texture, bulk density; soil organic matter content; pH value; soil moisture (water content/water tension); pore volume; macroporosity and air and/or water conductivity.

Evaluation of soil compaction effects on soil biota and soil biological processes in soils

The global importance of grasslands is indicated by their extent; they comprise some 26% of total land area and 80% of agriculturally productive land. The majority of grasslands are located in tropical developing countries where they are particularly important to the livelihoods of some one billion poor peoples. Grasslands clearly provide the feed base for grazing livestock and thus numerous high-quality foods, but such livestock also provide products such as fertilizer, transport, traction, fibre and leather. In addition, grasslands provide important services and roles including as water catchments, biodiversity reserves, for cultural and recreational needs, and potentially a carbon sink to alleviate greenhouse gas emissions. Inevitably, such functions may conflict with management for production of livestock products. Much of the increasing global demand for meat and milk, particularly from developing countries, will have to be supplied from grassland ecosystems, and this will provide difficult challenges. Increased production of meat and milk generally requires increased intake of metabolizable energy, and thus increased voluntary intake and/or digestibility of diets selected by grazing animals. These will require more widespread and effective application of improved management. Strategies to improve productivity include fertilizer application, grazing management, greater use of crop by-products, legumes and supplements and manipulation of stocking rate and herbage allowance. However, it is often difficult to predict the efficiency and cost-effectiveness of such strategies, particularly in tropical developing country production systems. Evaluation and on-going adjustment of grazing systems require appropriate and reliable assessment criteria, but these are often lacking. A number of emerging technologies may contribute to timely low-cost acquisition of quantitative information to better understand the soil-pasture-animal interactions and animal management in grassland systems. Development of remote imaging of vegetation, global positioning technology, improved diet markers, near IR spectroscopy and modelling provide improved tools for knowledge-based decisions on the productivity constraints of grazing animals. Individual electronic identification of animals offers opportunities for precision management on an individual animal basis for improved productivity. Improved outcomes in the form of livestock products, services and/or other outcomes from grasslands should be possible, but clearly a diversity of solutions are needed for the vast range of environments and social circumstances of global grasslands.

The importance of grasslands for animal production and other functions: a review on management and methodological progress in the tropics

tronic capacitance meter, rising plate meter, and simple pasture ruler. Accurate assessment of forage mass in pastures is key to budgeting The electronic capacitance meter relies on differences forage in grazing systems. Our objective was to determine the accuracy of an electronic capacitance meter, a rising plate meter, and a pasture in dielectric constants between air and herbage. The meruler in measuring forage mass and to determine the cost of measure- ter measures the capacitance of the air–herbage mixture ment inaccuracy. Forage mass was estimated in grazed pastures on (Curie et al., 1987) and responds mainly to the surface farms in Pennsylvania, Maryland, and West Virginia in 1998 and 1999. area of the foliage (Vickery and Nicol, 1982). The rising Forage mass estimated by each method was compared with forage plate meter integrates sward height and density into one mass estimated by hand-clipped samples. None of these indirect meth- measure, often called bulk height or bulk density (Miods were accurate or precise, and error levels ranged from 26 to 33% chalk and Herbert, 1977). Pasture rulers rely on a positive of the mean forage mass measured on the pastures. The computer relationship between forage yield and canopy height. model DAFOSYM (Dairy Forage System Model) was used to simuCommercially available meters come with factory late farm performance and the resulting effects of inaccuracies in calibrations; however, the accuracy and precision of estimating forage mass on pasture. A representative grazing dairy farm was developed, and the costs and returns from low-input and these equations have not been evaluated for Northeast conventional managements were calculated. Different scenarios were pasture conditions. Many studies of double-sampling then simulated, including under- or overestimating forage yield on techniques have shown that these techniques require pastures by 10 or 20%. All scenarios simulated resulted in lower frequent calibration and that universal equations for returns compared with the optimum farm, with decreases in net return estimating pasture mass may be unreliable (Frame, ranging from $8 to $198 ha 1 yr 1 . Underestimating forage mass re- 1993).

Estimating Forage Mass with a Commercial Capacitance Meter, Rising Plate Meter, and Pasture Ruler

The understanding and quantification of the impact caused by soil use and management on the physical soil quality are fundamental for the development of sustainable agricultural systems. The objective of this research was to quantify some physical soil properties to evaluate the physical quality of a dystrophic Red Latosol (Rhodic Ferralsol) in the northwest of the State of Parana, Brazil. Undisturbed soil samples were collected from two contiguous areas on an Experimental Farm of the State University of Maringa. One area was cultivated with annual crops under conventional tillage (disk plow and harrowing) and the other under native forest (semidecidual seasonal forest). The evaluated physical soil attributes were soil porosity and bulk density, soil water retention curve, soil resistance curve, and the least limiting water range. Results indicated significantly higher values of bulk density and lower values of soil porosity in the cultivated area. The soil water retention curve was not influenced by the soil use system, but was negatively influenced by bulk density. The soil resistance curve was influenced by the soil use system, evidenced by high values of soil resistance to root penetration under increasing drought in the cultivated soil. The least limiting water range was significantly smaller in the cultivated soil owing to the soil resistance to root penetration and air-filled porosity, which determined the lower and upper limits of soil water availability with bulk density increase. In the soil under native forest, the least limiting water range was equal to the water availability determined by the field capacity and the permanent wilting point. Soil compaction in the cultivated soil induced changes in the soil porous system, which were described by lower values of the least limiting water range than in virgin soil.

/pdf/propriedades-fisicas-de-um-latossolo-vermelho-distrofico-38evhn3a9b.pdf

Propriedades físicas de um Latossolo Vermelho distrófico cultivado e sob mata nativa

A single-probe capacitance meter (Pasture Probe), the Hill Farm Research Organization (HFRO) sward stick, a rising-plate meter, and cut quadrats were used to estimate herbage mass of swards that were rotationally grazed by cattle, cattle followed by topping, cattle followed by sheep, or sheep alone during 1989 and 1990 grazing seasons. Mean target pre- and post-grazing herbage masses were 2200 and 1100 kg dry matter (DM) ha−1 respectively. Linear regressions, correlations and scatterplots were calculated relating meter and sward stick readings to herbage mass on an ash-free organic matter basis measured by cutting quadrats of herbage at ground level.



Mean coefficients of variation for quadrat, capacitance meter, sward stick and rising plate were 28·8, 15·5, 27·2 and 27·9% respectively for pre-grazing herbage mass measurements, and 20·2, 10·1, 21·4, and 18·4% respectively for post-grazing measurements. These coefficients indicate that the capacitance meter varied less in estimating pre- and postgrazing herbage mass than the other three methods.



Correlation coefficients relating cut quadrats to capacitance meter, sward stick and rising plate readings were 0·65, 0·70 and 0·72 for pre-grazing, and 0·36, 0·31 and 0·05 for post-grazing herbage mass measurements respectively.



The non-destructive methods provided quick herbage mass estimates at a level of precision adequate for making day-to-day grazing management decisions on farms.

A comparison of quadrat, capacitance meter, HFRO sward stick, and rising plate for estimating herbage mass in a smooth‐stalked, meadowgrass‐dominant white clover sward

This experiment was carried out to study the responses of sward components (particularly white clover, Trifolium repens) to grazing management in a natural sward dominated by smooth-stalked meadowgrass (Poa pratensis) syn. Kentucky bluegrass. Treatments during two grazing seasons (1989–90) were: cattle grazing alone (C); cattle grazing followed by topping (CT); cattle grazing followed by sheep grazing (CS); and sheep grazing alone (S). Mean target pre- and post-grazing herbage masses were 2200 and 1100 kg DM ha−1, estimated by single-probe electronic capacitance meter. Sward component dynamics were monitored using turf dissections, marked white clover stolons, and ring-toss white clover leaf counts. Component and sward data for the C, CT, CS and S treatments respectively, were: number of white clover leaves m−2, 1295, 1384, 1408, 900 (s.e. ± 108); number of leaves per growing point, 3·2, 3·4, 3·0, 2·8 (s.e. ± 0·2); herbage accumulation (t DM ha−1), 5·16, 5·02, 5·87, 8·28 (s.e. ±0 08); rejected herbage (% pasture area) 39·7, 7·7, 16·0, 0 (s.e. ± 75); and annual net herbage production (t DM ha−1) 3·39, 4·35, 4·99, 8·28 (s.e. ± 0.07). Swards grazed by sheep alone contained less white clover, but regrew quicker and produced more herbage than other treatments. Close topping or grazing by sheep following dairy cattle grazing decreased sward rejection by cattle. These treatments maintained more of the pasture in better condition for subsequent cattle grazing, resulting in greater net herbage production than where no post-cattle grazing treatment was used.

Sward dynamics of a smooth‐stalked meadowgrass dominantwhite clover sward rotationally grazed by cattle and/or sheep

This experiment was carried out to improve understanding of sward and soil responses to cattle and/or sheep rotational grazing of low-input (no N fertilizer), natural swards dominated by smooth-stalked meadowgrass (Poa pratensis) syn. Kentucky bluegrass and based on white clover (Trifolium repens). Treatments during two grazing seasons (1989–90) were: cattle grazing alone (C); cattle grazing followed by topping (CT); cattle grazing followed by sheep grazing (CS); and sheep grazing alone (S), Mean target pre- and post-grazing herbage masses were 2200 and 1100 kg dry matter (DM) ha−1. Plants in sheep-grazed swards regrew more quickly and accumulated more herbage (8·28 compared to 5·35 t DM ha−1 for cattle-grazed swards, unadjusted for rejected area) than in other treatments. After 2 years, soil in sheep-grazed areas contained 0·25% N, 5·7 kg available P ha−1, and 379 kg K ha−1, compared to an average of 0·19, 3·9, and 179 respectively for the same soil nutrients in cattle-grazed treatments. Besides differences in manure distribution and sward rejection, differences in soil compaction among treatments also may have affected soil organisms and thus plant growth. After 2 years, soil bulk densities (g cc−1) were 1·37, 1·37, 1·27, and 1·12; soil penetrometer measurements (kg cm sec−1 sec−1) to 20-cm soil depth were 9·8, 9·3, 9·5, and 6·7; soil nematodes per 100 g of soil were: 5333, 8705, 2810, and 15208; soil rotifers per 100 g soil were: 288, 242, 715, and 33; and earthworms m−2 (and their biomass (g m−2)) were 262 (205), 157 (162), 344 (409), and 294 (343) for C, CT, CS, and S treatments, respectively.

Cattle and sheep grazing effects on soil organisms, fertility and compaction in a smooth‐stalked meadowgrass‐dominant white clover sward

Permanent pastures on acid soils in the northeastern USA produce far below their potential due to lack of legumes in the swards. This experiment was done to study the effects of lime-pelleted white clover seed and fertilizer combinations (B, Cu, K, Mg, Mo, P, S and Zn) on clover nodulation and growth in four acid (pH 4.3–4.9), Vermont permanent-pasture soils in the greenhouse. Potassium was applied in all treatments. Lime pelleting and Mg and P fertilization increased both proportion of plants nodulated and seedling weight. Lime pelleting resulted in the largest increase in nodulation but P application produced the greatest gain in seedling weight. Molybdenum interacted with P to enhance seedling nodulation more than either element applied alone. Phosphorus also interacted with Mg to increase seedling weight more than either one applied alone. Sulphur had no influence on seedling nodulation or yield. Applications of B, Cu and Zn depressed nodulation and yield, possibly because excessively high levels were applied. Using lime-pelleted seed and a fertilizer combination of K. Mg. Mo and P could improve white clover establishment and growth on permanent-pasture soils in the northeast.

Fertilizer and lime‐pellet requirements for seed of white clover used for improving permanent pastures†

Soil tests are used to predict fertilizer and liming needs of legumes being introduced into permanent pastures. However, the routine drying of soil samples may change the soil characteristics so much that recommendations based on test results may be poorly related to actual plant needs in the field. Test results from four soils, based on dried and moist samples, were related through stepwise multiple regression to percent nodulation and dry weight of white clover (Trifolium repens L. ) seedlings grown on soil cores in the greenhouse. Highly variable test results were obtained for Al, Mn, and P, depending on if a sample was dried or maintained moist. These discrepancies have implications for making P fertilizer and liming recommendations. Test results for other elements also varied widely. Extractable Mn and P accounted for most of the variation observed in percent nodulation, whether soil samples were dried or not. There was a significant interaction of P, Al, and Mn extracted from dried soils wi...

Problems in predicting legume fertility needs in steeplanl pasture improvement with soil tests 1

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