Concern for human safety and environmental contamination due to the inefficient use of plant protection products for orchard spraying has resulted in a range of practical models aimed at minimising the orchard-to-orchard variation of deposit through suitable adjustment of the label-recommended dose rate (LRDR) to different crop structure parameters. This study establishes a methodology for optimising model selection by using an appropriate database of crop structure measurements. LIDAR recordings of different orchards at different farms and growth stages have been used to construct an exemplar database of UK pome fruit structures. These recordings were processed initially to reduce each database entry to a set of four parameters describing the tree-row structure, namely: spacing, height, width and area-density. An exact model of LRDR adjustment, assuming minimum spray volume loss and based on all four tree-row structure parameters, was used as a comparator to evaluate the relative performance of different approximation models (i.e. typical regression models based on a reduced set of tree-row parameters). Various approximation models that included the scaling effects of tree-row area-density gave significant agreement with the population of LRDR adjustments predicted by the exact model. The following models gave the best agreement in their class for the percentage of adjustments correctly predicted to within an error tolerance ±1/8th LRDR (i.e. 80% for the tree-row area-density model and 93% for the combined adjustment model based on tree-row height and area-density). Other approximation models of practical interest gave less significant agreement with the exact model (i.e. 66% for the tree-row-volume model, 55% for the fruit-wall-area model, 50% for the constant adjustment model, 5% for no adjustment). Unfortunately, the practice of LRDR adjustment is currently undermined by many plant protection products that do not give the appropriate reference conditions necessary to define the worst-case crop structure for which acceptable biological performance may be achieved at the full LRDR. Only products aimed at uses in conjunction with integrated pest management schemes give this type of information and typically for use with specific models of LRDR adjustment that ignore the important scaling effects of area-density.

The recommended dose for many pesticides is expressed as a constant mass or volume per unit ground area covered by the crop. This method of dose expression is well suited to boom spraying where a reasonably uniform horizontal distribution of deposit can be achieved with a well-adjusted sprayer. However, in many practical situations (e.g. broadcast spraying of apple trees or other row structures where the spray application is made from within the canopy) the horizontal deposit distribution is strongly influenced by the crop area density and other crop structural parameters. This paper describes a generic method of pesticide dose expression to investigate these effects. The method incorporates a model of the spray volume deposition process. The model assumes that the pesticide deposit is proportional to the tank-mix concentration of pesticide. The model also assumes that spray volume deposit is proportional to the applied spray volume per unit row length and is inversely proportional to a crop length scaling function L (i.e. a parameter with the units of length that is expressed as a generic function of different crop parameters). The useful working range of this model is bounded by the condition for high spray volume where target losses become significant due to saturation and the condition for very low volume where evaporative transport losses become significant. Within this framework, four different models are formulated using first-order approximations for the length-scale as functions of the following crop parameters: tree row spacing, tree row height, tree area density and tree row volume to ground area ratio. Published measurements of crop structure and spray volume deposit on apple trees are compared with the output from these models. Light detection and range (LIDAR) measurements of apple orchards are presented and used in conjunction with the different models to predict pesticide use associated with different methods of dose expression. The results demonstrate the relative potential for varying the pesticide application rate according to the different crop parameters. The results enable the identification of reference orchards that could be used to establish worst-case pesticide application rates for registration purposes. The results also enable the identification of other orchards and growth stages where pesticide application rate might be reduced by up to a factor of five and give the same pesticide deposit as the reference structure.

This paper reviews the models of spray volume deposition that have been developed to enable the adjustment of pesticide output from an axial fan sprayer to suit different apple orchards. The review has been limited to the empirical models of leaf deposit D formulated as D=Q/UL, where L is a length-scale that describes the scaling effect of crop structure and Q/U is the ratio of the spray volumetric flow rate to sprayer speed which defines the volume application rate on a per unit row length basis. The comparative performance of different models was evaluated using field measurements of leaf deposit on Cox apple trees with different combinations of rootstock, plantation density, age and growth stage. A tractor-mounted light detection and ranging (LIDAR) system was used to record orchard structural detail. Different methods for calculating the length-scale L from this information have been developed based on a range of different orchard crop structural parameters. Linear regression analysis of the measurements showed that the standard method of adjusting pesticide output, based on a linear scaling of the spray volume application rate per unit ground area, accounted for only 9% of the variation in the measurements. The use of other models, based on different geometric scaling parameters of orchard structure were demonstrated to give improved correlation with measurements. Of these models, the best correlation was obtained by using a length-scale proportional to the ratio of the tree volume to total ground area and this accounted for 43% of the variation in the measurements. The use of orchard structure parameters, based on crop area estimates derived from a local Poisson distribution of light transmission, gave further improvements. Of these models, the best correlation was obtained with a length-scale proportional to the tree area density and this accounted for 78% of the variation in the measurements. The tree area density is thus the best single crop structure parameter to use as the basis for pesticide dose expression for the practices of apple orchard spraying represented by these measurements. The calculation of this parameter relies on the availability of LIDAR measurements. Alternatively, a simple method for estimating this parameter might easily be constructed as a pictograph showing the relative tree area density associated with orchard tree images that can be reconstructed from these measurements. This research further identifies the need for this type of crop structural information to improve standardization of the dose recommendations on pesticide labels.

This paper presents the measurements of dwarf and semi-dwarf Cox apple trees with a tractor-mounted LIDAR (Light Detection and Ranging). An analysis is presented which derives structural parameters of the canopy for use in pesticide spraying research by considering the number flux of LIDAR scans intercepted by the crop in a known spatial segment. LIDAR measurements of the crop area normalised by the horizontal projected area of the crop are compared with measurements derived from a destructive sampling method. The distributions of local crop area density and crop interception probability are also presented. Crop area density distribution can be used to estimate the deposition distribution of spray by utilising a suitable transport and deposition model. Alternatively, crop interception probability distribution can be used as a first order estimate of the spray deposition distribution by making an analogy between tight and spray transmission.

Laboratory studies of the effectiveness of rotary cutting mechanisms when cutting singleand groups of grass stems were undertaken. The effect of using static stem supports or ledger plates with clearances of up to 5 mm from the cutting blade was investigated. The effectiveness of cutting with single-toothed and plain discs was also examined. The effect of clamping the tops of grass stems was examined for both types of mechanism. A number of mechanism design parameters was investigated and cutting efficacy was assessed by measuring the stubble length of individual stems, together with the number of stems which were uncut, pulled out of the holder or broken at their base. The critical speed, which is the minimum required for efficient cutting, was also assessed.

Extensive experiments were conducted in the field to examine the performance of toothed discs when mowing a wide range of grass crops. The work was performed using (1) a modular rig fitted with six discs, (2) a two-drum mower fitted with toothed annuli and (3) a five-disc mower-conditioner modified to accommodate toothed discs. Mowing performance was studied over a range of forward speeds from 2 to 12 km/h and at tooth tip speeds up to 80 m/s. Tooth pitch was varied over a range up to 25 mm. Performance was compared with that of commercial drum and disc mowers using conventional blades. The efficacy of mowing was measured by samples of the length of stubble produced and the power consumption of the mowers. Studies were also made of the wear of the disc teeth during mowing.

AbstractA lime requirement test termed the dual‐buffer titration (DBT) was developed for acid minesoils occurring in Pennsylvania. The DBT uses two buffers to stoichiometrically account for contributions of hydrogen ions (H+) to soil acidity to pH 7.0, including those from the hydrolysis of Al. The first buffer lowers the soil pH to 3.17 to dissolve Al‐OH polymers, amorphous coatings, and interlayer species. The second buffer raises the pH to approximately 8.2, titrating the exchangeable Al3+ and other hydrolyzed species to neutralized forms. Lastly, a titration of the buffers‐soil mixture with standardized base to pH 8.2 provides a direct measure of the lime requirement. For comparison, a 5‐month CaCO3 incubation of 31 soils was also determined. The results by the two methods were highly correlated (r = 0.92) for 24 samples and statistically the same at a probability level of 0.001.

Although the basic chemistry and behavior of potassium in the soil is well understood, little of this knowledge is used in soil testing and practical soil fertility mangement. In this study the K buffer behavior of three individual soils (Hagerstown silt loam (Typic Hapludalf), Gatesburg sand (Entic Haplorthod) and Gilpin channery silt loam (Typic Hapludult)) was investigated. The buffer relationships determined indicated very different K behavior for these soils even though exchangeable K soil tests indicated similar K levels. It was also determined that for these soils the buffer relationship was apparently independent of previous K management, indicating that the K buffer behavior could be included as part of soil characterization data. The role of nonexchangeable K in determining K buffer behavior was also investigated. It was found that the levels of solution K where the release of nonexchangeable K becomes measurable (0.27 ‐ 0.83 × 10‐4 M) are similar to solution K levels reportedly required for crop growth (0.02 ‐ 0.95 × 10‐4 M). It was also found that these soils were capable of maintaining a relatively high level of exchangeable K even after extraction of significant amounts of nonexchangeable K with sodium tetraphenyl boron. It was concluded that K buffering behavior of individual soils could and should be included in K management decisions involving corrective soil treatments and/or crop removal estimation. Otherwise, based on current soil tests, soils with very different K buffer behavior will be treated similarly.

AbstractA greenhouse experiment was conducted to determine (i) the physical and/or chemical properties of soils which control Cu availability; (ii) if 0.0004M DTPA (diethylenetriaminepentaacetic acid) effects a small exchange of Cu in soils; and (iii) if pCu, estimated by iterative computer calculations based on DTPA stability constants, reflects the availability of Cu in soils. The growth and Cu accumulation of corn seedlings were studied using 16 northeastern United States soils, each treated to contain 125, 250, and 500 ppm total Cu. Soil pH, percent organic matter, cation exchange capacity (CEC), percent clay, percent silt, percent sand, percent Na2O, and DTPA‐extractable Cu were measured in order to relate soil properties to Cu availability and seedling growth.The soil factors affecting the mean soil Cu activity coefficient and therefore controlling Cu availability were pH and the silt fractions of Na‐bearing minerals. The DTPA at 0.0004M with a 1:10 soil‐to‐solution ratio did not effect a small exchange for Cu. For most soils, the DTPA extracted the labile Cu. Finally, when medium and fine‐textured soils are tested by the Baker DTPA soil test, resulting pCu values of approximately 11.9 and less should in general indicate high soil Cu availability (i.e., soil Cu availability ≧ 0.16 ppm) and reduced corn growth.

In a Morrison sandy loam marginal in boron, fertilization with 1.1 ppm boron increased the shoot dry weight of mycorrhizal red clover (Trifolium pratense L.) an average of 16%, but did not affect nonmycorrhizal clover weight. Root colonization and foliar phosphorus concentrations were not significantly affected by B deficiency. With alfalfa (Medicago sativa L.) and Morrison soil in which B deficiency had been intensified by the addition of 100 ppm nitrogen as NH4NO3, inadequate B reduced the shoot dry weight of mycorrhizal plants 71%vs a reduction of 35% for nonmycorrhizal plants. Boron deficiency was more severe in the earlier cuttings and delayed the onset of mycorrhizal infection and the subsequent spread of mycorrhizal fungi within the roots. This delay may contribute to the lower concentrations of P and Cu seen by others during early developmental stages of B-deficient alfalfa.

SummaryIn three field soils, birdsfoot trefoil (Lotus corniculatus L.) transplants infected with mycorrhizal fungi from 42 soils showed no clear superiority of strains from these individual soils after a year's growth. Differences among strains decreased with time and were only significant for all three soils at the first cutting. There were low‐level correlations between yield and various chemical properties of the soils from which the cultures were derived. In the greenhouse, with sterilized soils low in P, trefoil yield was always greatest when the inoculum used was indigenous to the soil in which the plants were grown as compared to inocula from five different soils. These results suggest that indigenous strains of mycorrhizal fungi may possess an adaptation to edaphic factors and that the performance and persistence of strains otherwise more efficient in nutrient uptake may be limited by their lack of adaptation.

This paper discusses the opportunities to combine the efforts of plant geneticists and soil scientists to develop crop varieties adapted to the existing soil conditions and techniques used for production. Such research should result in improved varieties for the best as well as poorest of soil and production situations.

A greenhouse study was conducted to evaluate alfalfa (Medicago saliva L.) clones for phosphorus efficiency and to assess the interactions of mycorrhizal inoculation and plant genotype as they affect shoot weight and element concentrations. Six clones from each of six cultivars were grown in partially sterilized, low‐P soil treated with either 0, 30, or 80 ppm P, O P and mycorrhizal inoculum, or 80 ppm P and mycorrhizal inoculum. In the O P treatments, plant growth without mycorrhizae was significantly less than growth of mycorrhizal (MR) plants, while at 80 ppm P growth of nonmycorrhizal (NMR) plants was greater than growth of the corresponding MR plants for most clones but less hi some. Cultivar ✕ MR and clones in cultivar ✕ MR interactions for plant growth were significant. Maximizing P deficiency to select P‐efficient clones was unsuccessful as dry weights of nonmycorrhizal, low‐P plants were not correlated with dry weights of any other treatments, and only the two mycorrhizal treatments were highly correlated. At the 80 ppm level of P, mycorrhizae increased P, Cu, Zn, and Fe, decreased Mg and Ca, and did not affect Mn and K concentrations. Cultivar ✕ MR interactions were significant for Cu and Zn concentrations and clones in cultivars ✕ MR interactions were significant for all elements. These results indicate that screening of alfalfa lines for P efficiency or for content of P, Cu, and Zn should be conducted under natural (mycorrhizal) conditions.

AbstractMycorrhizae increase the uptake of Zn and Cu by many plants, but mycorrhizal activity is suppressed by P fertilization. Soybean (Glycine max Mer.) and two lines of corn (Zea mays L.) were used to determine if this mechanism is a major cause of P‐induced Zn and Cu deficiencies. Shoot dry weights and concentrations or total uptake of P, Zn, Cu, Fe, Mn, K, Ca and Mg were determined for mycorrhizal and nonmycorrhizal plants given 0, 25, 75, or 200 ppm P. Phosphorus fertilization significantly reduced Zn and Cu concentrations in mycorrhizal soybeans, but concentrations in nonmycorrhizal treatments were not affected. Concentrations of Zn and Cu in mycorrhizal and nonmycorrhizal corn were reduced by P fertilization, but the reduction for mycorrhizal plants was significantly greater than the decrease for nonmycorrhizal plants. Reductions in Zn and Cu concentrations in nonmycorrhizal corn were the result of a dilution effect and could be attributed to increased plant size rather than increased P fertility per se. The concentrations of the other analyzed elements were all affected by P level and/or mycorrhizal condition. In general, mycorrhizal and non‐mycorrhizal dry weights and element concentrations converged as soil P was increased. Patterns of response to P and mycorrhizae differed slightly between corn lines, and such differences were marked for certain elements when corn was compared with soybean.

Soil Science Society of America JournalVolume 42, Issue 6 p. 987-988 Comment and Letter to the Editor Further Reflections on the Use of the Langmuir Equation in Soils Research Robert D. Harter, Robert D. Harter INER, University of New Hampshire, Durham, New Hampshire, 03824Search for more papers by this authorDale E. Baker, Dale E. Baker Department of Agronomy, Pennsylvania State University, University Park, PA, 16802Search for more papers by this author Robert D. Harter, Robert D. Harter INER, University of New Hampshire, Durham, New Hampshire, 03824Search for more papers by this authorDale E. Baker, Dale E. Baker Department of Agronomy, Pennsylvania State University, University Park, PA, 16802Search for more papers by this author First published: 01 November 1978 https://doi.org/10.2136/sssaj1978.03615995004200060036xCitations: 8AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinkedInRedditWechat No abstract is available for this article.Citing Literature Volume42, Issue6November-December 1978Pages 987-988 RelatedInformation

AbstractDonnán type ratios were used to develop an index to account for the differential adsorption of K in two widely different soils of the Rayne and Hublersburg series. This index was used to calculate an adjusted K requirement for the soils using the approach of Baker. Three corn hybrids (Zea mays L.) were grown in the two soils treated with different levels of K and multiple regression analysis was used to relate soil test variables to plant K content.Most of the variation in the index, KE/S, was associated with soil effects, making the index useful in characterizing the two soils with respect to differential K adsorption and in calculating soil K requirements. Over 60% of the variation in plant K content was explained by the soil K requirement calculated from the index. Compared with a critical K level of 98 ppm exchangeable K for soils with a CEC of 10 meq/100 g and a KE/S of 1.0, the comparable critical values for K were 71 ppm for the Rayne and 114 ppm for the Hublersburg.

AbstractThis investigation was conducted to measure the accumulation of cadmium (Cd), zinc (Zn), and copper (Cu) in the tissues of the meadow vole (Microtus pennsylvanicus) fed organic and inorganic cadmium. Corn (Zea mays L.) and sorghum (Sorghum bicolor L. Moench) plants were grown on soils fertilized with either inorganic or sludge fertilizer. Corn herbage fertilized with sludge was found to contain 1.82 ppm Cd and sorghum herbage contained 4.59 ppm Cd. Herbage from inorganic fertilized plots contained 0.17 ppm and 0.38 ppm Cd, respectively. Eight diets and a synthetic control diet were formulated to study these herbages. Cadmium sulfate was added to four of the diets to evaluate the effect of organic plant Cd and soluble Cd on accumulation in vole tissue. Each diet was fed to 10 animals for a period of 40 days and kidney, liver, and muscle tissue were analyzed for Cd, Zn, and Cu.Significant accumulation of Cd occurred in kidneys and livers, but not in muscles of voles fed sludge‐fertilized corn diets with 1.09 ppm Cd or sorghum diets with 2.76 ppm Cd. The form of Cd, whether organic or soluble, had little influence on tissue accumulation. Zinc and Cu accumulation in these tissues was, in most cases, nonsignificant and not associated with Cd accumulation. Weight gain, food intake, and diet digestibility were not influenced by Cd accumulation in the tissue, but the daily intake of Cd was a function of the concentration of Cd and fiber in the diet. It was concluded that diets containing 1.00 ppm Cd may cause significant accumulation of Cd in animal tissues.

AbstractSewage sludge samples were collected biweekly and analyzed for several components to determine the sampling procedures which should be required for the routine chemical monitoring of sewage sludge produced by a given treatment plant. While the composition varied significantly over time for every component and every plant, the standard deviation, expressed as a percentage of the mean for each treatment plant, indicated that two‐thirds of the values would be within the range of the true average value plus or minus 20 to 50%.Analyses for all samples collected in Pennsylvania, including those analyzed as a part of a service program, indicated that without chemical analysis the composition with respect to N, P, and K varied too much to establish an accurate prediction of the fertilizer value of unanalyzed sludge. In addition, the concentrations of the essential but phytotoxic elements, especially Zn and Cu, as well as trace elements harmful to the food chain, varied greatly among the treatment plants studied.

AbstractWhen the development of the Langmuir adsorption equation is critically examined, it is evident that the equation soil scientists have been using [C/x/m = C/k + I/kb, where C is concentration of adsorbate, x/m is the amount adsorbed per unit weight adsorbent, k is the adsorption maximum, and b is a constant] is in the wrong form. This error is of no great importance when the equation is merely used to obtain a calculated adsorption maximum for comparison to other adsorbent properties. However, it does become important when attempts are made to understand adsorption dynamics and bonding strengths. The commonly reported curvilinear nature of the C/x/m vs. C plots is simply the result of not considering the effect of desorbed ions in the equilibrium solution, rather than being due to multiple adsorption mechanisms. When the equation is corrected by considering desorbed ions, the isotherm becomes linear. In addition, the constant, b, of the Langmuir equation is not simply related to the bonding energy of the adsorbed ion, but to the ratio of adsorbed and desorbed ion bonding energies.