The South Florida Water Management District uses a computer model, the Field Hydrologic and Nutrient Transport Model (FHANTM), to estimate flow (runoff and subsurface lateral flow) and phosphorus (P) loads leaving agricultural fields in the Lake Okeechobee watershed. Uncertain knowledge of FHANTM parameter values leads to uncertainty in model estimates. This study used First Order Analysis (FOA) and Monte Carlo Simulation (MCS) to quantify uncertainty in model outputs. A sensitivity analysis was conducted to identify parameters that have the greatest effect on model output. Six parameters significantly affected model output and were used in the uncertainty analysis. In the case of surface runoff, FACTOR (monthly potential evapotranspiration factor) accounted for 64% of the uncertainty in terms of variance. For P concentrations in surface runoff, PADD (the mass of phosphorus added by animals each day) accounted for 79% of the uncertainty in terms of variance. Thus, improving knowledge of these parameters has a significant impact on reducing the uncertainty in the predicted runoff and phosphorus loads.

A major manufacturer of pendulum-action spreaders has suggested that the effective swath width of a pendulum spreader can be predicted adequately by merely measuring the total swath width and dividing by two. An experimental study with three granular materials demonstrated that this method did nor give an adequately uniform pattern. The predicted swath widths were wider than the optimum swath widths determined from pattern testing but narrower than the "normal" swath widths determined from pattern testing. The predicted widths resulted in patterns with unacceptable uniformity.

Subirrigated fresh market tomato production in Florida uses raised, plastic-mulched beds and has traditionally used large amounts of water and fertilizer to ensure achieving targeted yield levels. Water table levels are typically maintained within 40 to 45 cm (16 to 18 in.) from the soil bed surface requiring continuous water application through lateral field ditches spaced 6 to 12 m (20 to 40 ft) apart. Field experiments were conducted for three spring growing seasons to test the impact of controlled water table positions using the fully enclosed subirrigation (FES) system and reduced fertilizer applications on fresh market tomato production. The experiment consisted of controlled water table level treatments of 45, 60, and 75 cm (18, 24, and 30 in.) and three fertilization rate combinations of 215,309, and 403 kg N ha-1 and 248,356, and 465 kg K ha-1 (192,276, and 360 lb N acre-1 and 221,318, and 415 lb K acre-1), respectively based on 6542 bed m ha-1 (8686 bed ft acre-1) conducted over three growing seasons. Fruit yield and quality were used to determine the impact of applied fertilizer rates and water table levels. Results show comparable seasonal production levels were achieved among fertilizer rates and water table levels with no significant interactions among treatments. Lower target water table levels used in combination with lower application rates of fertilizer had no detrimental effect on yield and reduced the potential for fertilizer to be leached by excessive rainfall.

Four types of dual-function gates were used to semiautomate basin and border irrigation systems. These gates open to admit water to a field and then close to terminate irrigation. They were released or tripped by timers, electric solenoids or a trip-cord gate release system. Gate descriptions and construction information are presented for (1) dual-panel combination gates, (2) butterfly gates, (3) linear actuator-operated jack gate, and (4) pipe turnouts in unlined ditches. The gates were field tested in different basin and border systems. An improved border system with combination gates reduced irrigation time from five half-days to two, compared to the previous system which used siphon tubes. On a manual basis, prior to completion of the control system, irrigation application efficiency was 68%. A battery-powered linear actuator was an effective means of semiautomating a jack gate. A drop-closed gate on the inlet and a flexible droptube on the outlet of a pipe turnout provided a low-cost means of semiautomating irrigation in unlined ditches.

New York apples are annually threatened by a large number of pests. Air-carrier sprayers are generally used to apply materials to the trees to control these pests. Depending on the pest pressure and end use of the crop, four to eight different applications may be required during a growing season. Little information is available on how accurately air-carrier sprayers designed to treat orchards are being used This study was designed to provide information to growers, educators, and manufacturers on how well air-carrier sprayers were being used in western New York orchards during 1990 and 1991. The growers agreeing to participate in this study had a history of some pest control problems as identified by extension pest management specialists. In this study of the 45 calibrations made for different spraying situations, only 11 (24%) were within 5% of the intended application rate expressed by the growers. Nozzle wear and nozzle pressure were the primary factors contributing to the misapplication errors. In a visual evaluation of spray coverage for each treatment, higher spray coverage ratings were given when application rates exceeded 467.3 L/ha (50 gall acre). Spray coverage ratings were generally lower on leaf undersides and on the inside portions of trees.

Pressure transducers and mercury-water manometers were simultaneously connected to nine tensiometers installed in a forest soil plot in the Ouachita Mountains of central Arkansas. Simultaneous measurements of soil water potential were compared during three simulated storms. Plots of soil water potential measured by the two sensors through time indicated systematic differences due to a lag in the response of the manometers to rapidly changing soil water potentials and hysteresis effects of the transducers. Nonparametric analysis was used to statistically analyze the systematic differences. Despite the fact that significant and systematic differences were found, the differences were generally small and within the bounds of precision expected in field installations. Differences between the two methods were less than or equal to 50 mm (2 in.) of water for 63%, greater than 50 mm (2 in.) and less than or equal to 100 mm (4 in.) of water for 34% and greater than 100 mm (4 in.) and less than 120 mm (4.7 in.) of water for 3% of 804 pairs of soil water potential measurements. For the specific equipment used and the environmental conditions encountered, pressure transducers provided measurements of soil water potentials that were comparable to those obtained by mercury-water manometers. Transducers also provide the advantages of quicker response names and the capability of remote recording by data loggers.

Shallow glacial outwash aquifers provide water to farms, towns, and major cities. The fact that overlying soils are shallow and provide little protection from leachable chemicals suggests the need for careful management of chemical use. This research was conducted to provide data on the leaching potential of 2,4-D and picloram applied to road ditches over shallow aquifers. A comparison of soil profiles in the ditch and adjoining field indicated that an average of 0.3 m (1 ft) of soil was removed from road ditch soils, leaving very shallow soil profiles over the aquifer material. Cumulative infiltration of water into side slopes and ditch bottoms was measured on representative soils together with gravel road runoff to determine a water balance for the ditch. Undisturbed soil columns were brought into a greenhouse where leaching water could be collected and analyzed for the herbicides, 2,4-D and picloram, the currently used herbicides, which had been applied at recommended rates. The combination of extra leaching water from road runoff added to direct rainfall, and the naturally shallow soils that have been reduced in depth to build the roadbed resulted in two to five times the water passing through to groundwater than through adjoining fields. From 2 to 33% of the applied herbicides came through the undisturbed soil columns after the first storm event. The results indicate that caution should be exercised if the choice is made to use chemical methods of weed control in road ditches.

This article describes the effects of truck vibration on bruising in apples. Four different types of cartons were evaluated. The interior packaging consisted of expanded polystyrene (foam) trays, paper pulp trays, and two different types of paperboard trays. The vibration levels were simulated for truck-trailer systems with leaf spring and air cushion suspensions traveling on interstate expressways. Bruises were measured in the packages tested. The results showed that the foam tray was the best type of interior packaging followed by the paperboard partitions. The paper pulp tray produced the highest damage levels. The air cushion truck suspension showed lower damage levels than the leaf spring suspension for all package types.

Types of controls and displays, and the considerations for locating these for an experimental battery-powered chore tractor, designed and developed at South Dakota State University, are discussed. The locations of controls and displays were evaluated through physical measurements and subjective assessment. Factors that are important in locating controls and displays in a battery-powered tractor are discussed.

Four lots of F1-hybrid seed corn were dried in laboratory dryers to help understand the performance of a commercial Wisconsin bin-system dryer. Two airflow direction reversal strategies were studied Drying temperatures were 35 and 40.5 degrees C (95 and 105 degrees F) in two dryers and 40.5 and 46 degrees C (105 and 115 degrees F) in two other dryers. Germination and energy use were not affected by the differences in drying air temperature or airflow direction reversal strategy. Drying times averaged 22% less with the higher drying air temperatures. Decreased drying time due to increased drying temperatures resulted in a 28% increase in drying capacity on the average. Final moisture gradients were greater with increased drying temperatures because airflow direction reversal was not timed properly when using the higher drying air temperatures.