AbstractHealthy soil air–water balance is critical for crop growth. Conservation agricultural practices improve soil physical properties to influence soil oxygen availability. We evaluated the impact of 42 years of hairy vetch (HV) cover cropping (CC), and no‐tillage (NT) on soil oxygen dynamics during a cotton growing season experiencing multiple intensive rain events in silt loam soil. The HV and NT treatments exhibited higher growing season soil oxygen availability (p < 0.05) and experienced three to four times fewer hours of oxygen limitation (i.e., oxygen concentration <10%) as compared to no cover crop (NC) and conventional tillage (CT) treatments. After a heavy rainfall, NT–HV treatment exhibited the highest soil oxygen availability, followed by NT–NC, CT–HV, and CT–NC treatments (p < 0.05). While CC and/or NT treatments quickly regained soil oxygen status within 24 h after saturating rain events, CT–NC suffered from sub‐optimal soil aeration until the third day after rainfall cessation. The combination of CC with NT practices enhanced soil oxygen availability and resilience to extreme precipitation events.Core Ideas Long‐term cover cropping and no‐tillage practices enhanced soil oxygen availability following extreme precipitation events. Cover cropping and no‐tillage practices reduced the duration of anoxia experienced by cotton crops during the growing season by three‐ to four‐fold. Combined cover cropping and no‐tillage implementation exhibited the most significant impact in mitigating immediate soil oxygen stress after heavy rainfall events.

Trunk boring insect pests can cause severe plant damage and death thus causing nursery operators to incur significant economic losses. In order to control trunk borers with contact insecticides, thorough coverage is presumed necessary. While not designed for trunk applications, nursery operators commonly use air-blast sprayers for this purpose due to their high labor efficiency and perceived ability to adequately spray trunk and canopy pests simultaneously. This study quantified spray deposits on red maple trunks in a 3-row block at two application rates, 1380 and 1070 L ha(-1), from a vineyard air-blast sprayer equipped with laboratory-designed 5-port nozzle bodies known to improve coverage uniformity. Water sensitive wraps placed at four heights (11.4 to 77.5 cm) on trunks in each row were analyzed for coverage after spraying the block from both sides with all 20 nozzles on the proximal side of the sprayer. While there was a row x direction x height interaction (p=0.0304), within each row, portions of wraps facing the same direction did not differ in coverage regardless of height. On the interior row only, coverage was greater at 1070 than at 1380 L ha(-1) (p<0.0001), possibly due to zero wind allowing greater penetration into the interior row. For both rates, while the face of the trunk proximal to the sprayer in the exterior rows had high coverage, ranging from 77 to 95%, the opposite side averaged just 38% coverage, resulting in a total coverage of only 53% on average. High coverage is possible for a wide range of trunk heights on the proximal face of exterior rows; however, for a 3-row block of trees, applications of 1380 L ha(-1) or less from this specialized sprayer may not achieve 100% coverage around the entire trunk. Further optimization to sprayer type, technology, and adjustments, such as application rate, should be explored.

AbstractAir-blast sprayers have known inefficiencies in nursery production systems. Intelligent, variable-rate spray technology aims to improve application accuracy and reduce total pesticide consumption by utilizing pulse-width modulated solenoid valves, laser scanning and ground speed sensors, and a computerized algorithm to customize spray output based on plant presence, size, shape, and density. This study used an air-blast sprayer retrofitted with this variable-rate spray technology to directly compare spray characteristics and pest control of the sprayer operated in intelligent, variable-rate mode and conventional, constant-rate mode to spray trees grown in 57 L (15 gal) containers in a multi-row pot-in-pot production system. Variable-rate mode reduced total spray volume by 43% while providing equivalent, and at times better, disease control compared to the constant-rate mode for two fungal borne diseases of Shumard oak (Quercus shumardii Buckley). This research demonstrates the capability of variable-rate technology to reduce input costs, environmental harm, and risk of pesticide exposure while simultaneously controlling disease and maintaining saleable crops.Species used in this study: Shumard oak (Quercus shumardii Buckley).

Terrestrial LiDAR (light detection and ranging) has been used to quantify micro-topographic changes using high-density 3D point clouds in which extracting the ground surface is susceptible to off-terrain (OT) points. Various filtering algorithms are available in classifying ground and OT points, but additional research is needed to choose and implement a suitable algorithm for a given surface. This paper assesses the performance of three filtering algorithms in classifying terrestrial LiDAR point clouds: a cloth simulation filter (CSF), a modified slope-based filter (MSBF), and a random forest (RF) classifier, based on a typical use-case in quantifying soil erosion and surface denudation. A hillslope plot was scanned before and after removing vegetation to generate a test dataset of ground and OT points. Each algorithm was then tested against this dataset with various parameters/settings to obtain the highest performance. CSF produced the best classification with a Kappa value of 0.86, but its performance is highly influenced by the 'time-step' parameter. MSBF had the highest precision of 0.94 for ground point classification but the highest Kappa value of only 0.62. RF produced balanced classifications with the highest Kappa value of 0.75. This work provides valuable information in optimizing the parameters of the filtering algorithms to improve their performance in detecting micro-topographic changes.

The advances of remote sensing techniques allow for the generation of dense point clouds to detect detailed surface changes up to centimeter/millimeter levels. However, there is still a need for an easy method to derive such surface changes based on digital elevation models generated from dense point clouds while taking into consideration spatial varied uncertainty. We present a straightforward method, Las2DoD, to quantify surface change directly from point clouds with spatially varied uncertainty. This method uses a cell-based Welch’s t-test to determine whether each cell of a surface experienced a significant elevation change based on the points measured within the cell. Las2DoD is coded in Python with a simple graphic user interface. It was applied in a case study to quantify hillslope erosion on two plots: one dominated by rill erosion, and the other by sheet erosion, in southeastern United States. The results from the rilled plot indicate that Las2DoD can estimate 90% of the total measured sediment, in comparison to 58% and 70% from two other commonly used methods. The Las2DOD-derived result is less accurate (65%) but still outperforms the other two methods (30% and 48%) for the plot dominated by sheet erosion. Las2DoD captures more low-magnitude changes and is particularly useful where surface changes are small but contribute significantly to the total surface change when summed.

Highlights An automated irrigation system based on a novel leachate sensor was built to schedule and deliver irrigation to a container nursery. The sensor network was designed to achieve a 0.15 leaching fraction; it maintained an actual average leaching fraction of 0.17. Water use and container effluent were reduced by 60% and 96%, respectively, without reducing crop growth. Abstract. With the aim of reducing irrigation water use, an irrigation and leachate measurement and control system was developed and evaluated to automatically schedule and actuate irrigation in a commercial nursery. Leachate and irrigation sensors were built using a tipping bucket mechanism and used to calculate the daily leaching fraction (LF) = volume leached/volume applied. For the experimental daily irrigation schedule, the previous day’s LF was used to calculate irrigation run time for the current day using a scaled multiplier, where the change in irrigation run time was proportional to the difference between the calculated LF and the target LF, 0.15. The control zone was irrigated for two hours every other day simulating the commercial nursery’s standard schedule. The irrigation control system worked as designed and correctly imposed the irrigation treatments, including correctly delaying in response to rain and actuating based on a programmed minimum runtime, when necessary. Season-long water use was 60% less for the leachate-based irrigation schedule compared to the grower’s standard irrigation schedule (p = 0.0028). The average daily LFs were 0.17 and 0.73 for the LF-based irrigation and control, respectively (p < 0.0001). Compared to the grower’s standard practice the time averaged irrigation application rate was 3.3-fold less and time averaged leaching rate was 12.1-fold less for the LF-based irrigation schedule. Substrate volumetric water content was not correlated with LF and thus was not a good predictor of leaching fraction. Growth metrics were not impacted by irrigation treatment (p = 0.1429), indicating plants received sufficient water in the LF-based irrigation system. This novel system was able to actuate and adjust irrigation run-time based on daily leaching fraction without being influenced by the lag between irrigation and leaching and had an average leaching fraction within 0.02 of the target LF. Reducing water use with this LF-based schedule has the potential to reduce agrichemical-laden nursery effluent and increase nursery irrigation capacity, i.e., their ability to expand production on the current water supply. Keywords: Container effluent, ET-based irrigation, Irrigation schedule, Leachate, Precision irrigation, Sensor-based irrigation.

Learn how harvesting rainwater can enhance high tunnel crops and production.

Highlights Using leaching fraction to schedule irrigation is recommended yet no automated measurement system exists. Sensors were developed to automatically measure leachate and irrigation within a sensor network. There was no difference between sensor measured and manually captured volume for sensors deployed in a nursery. After deployment in commercial nurseries, sensors accurately measured leachate and irrigation within 10% margin. Abstract . Nursery crops are often over-irrigated, resulting in wasted water and agrochemical inputs. Irrigating based on leaching fraction is recommended, yet an automated system for measuring and recording nursery container effluent (leachate) does not exist. The objective of this research was to develop and test a sensor-based system for real-time leachate and irrigation measurement in outdoor commercial nurseries. Sensors were developed to automatically measure irrigation and leachate volume in container nurseries that use overhead irrigation with the goal of facilitating the development of an automated leaching fraction-based irrigation system. Sensors were built using readily available components, including tipping bucket mechanisms calibrated to either 4.7 or 8.2 mL per tip, and were designed and constructed to function with commonly used 3.8-, 11.4-, and 14.5-L nursery containers. Sensor networks were developed in order to collect data from the sensors. Sensors were deployed at three commercial nurseries and tested using closed- and open-loop tests. Initially, a closed-loop test was performed on a subset of the sensors to test the integrity of the sensor-container system when subjected to an overhead irrigation delivery system. Following closed-loop tests, sensors were subjected to tests utilizing directed applications of water to compare sensor measurements with the volume of water applied and to compare sensor measurements over time (pre- and post-season). There was no difference between leachate measured by sensors and leachate captured and measured manually in closed-loop tests (p = 0.0570). In directed applications, sensors measured water flow with less than 3% margin at the beginning of the season (p = 0.0485) and less than 10% margin at the end of the season (p = 0.0390) regardless of container size. Pre- and post-season comparisons showed equivalence at the 10% margin for the 4.7-mL tipping bucket size (p = 0.0043) and at 5% for those calibrated to 8.2 mL per tip (p = 0.0198). Sensors deployed in commercial nurseries accurately measured leachate and irrigation within a 10% margin in real-time, on an individual plant scale, making them a viable option for a leaching fraction-based irrigation schedule. Keywords: Container effluent, Container-grown plants, Leaching fraction, Irrigation schedule, Sensor network.

Nursery producers are challenged with growing a wide range of species with little to no detectable damage from insects or diseases. Growing plants that meet consumer demand for aesthetics has traditionally meant routine pesticide application using the most time-efficient method possible, an air-blast sprayer, despite its known poor pesticide application efficiency. New variable-rate spray technology allows growers to make more targeted applications and reduce off-target pesticide loss. In this study, a prototype laser-guided variable-rate sprayer was compared with a traditional air-blast sprayer. Pesticide volume, spray application characteristics, and the control of powdery mildew were evaluated over the course of two growing seasons. Spray application characteristics were assessed using water-sensitive cards (WSCs) and DepositScan software. This prototype sprayer reduced pesticide volume by an average of 54% across both years despite being tested against a low rate (<250 L⋅ha−1). In 2016, the conventional sprayer had more than double the deposit density on target WSCs among distal trees than the variable-rate sprayer; however, within proximal trees, there was no difference between the two sprayer types. In 2017, when the trees were larger, within both the distal and proximal trees, the conventional sprayer had greater deposit density on target WSCs than the variable-rate sprayer. In 2016, coverage on target WSCs was nearly 7-fold greater with the conventional treatment than with the variable-rate treatment. In 2017, when trees were larger, there was greater coverage on target WSCs in proximal trees (3.8%) compared with those in distal trees (1.0%) regardless of the sprayer type. This variable-rate spray technology provided acceptable control of powdery mildew severity on individual branches and whole trees and maintained the incidence of powdery mildew to levels comparable to that occurring among trees sprayed with a traditional air-blast sprayer. Therefore, the variable-rate spray technology has the potential to effectively control disease, dramatically reduce the pesticide footprint, and preserve natural resources such as ground and surface water, soil, and beneficial insects found within and around nurseries.

To optimize pesticide applications to the canopies of deciduous perennial crops, spray volume should be adjusted throughout the year to match the changes in canopy volume and density. Machine-vision, computer-controlled, variable-rate sprayers are now commercially available and claim to provide adequate coverage with decreased spray volumes compared with constant-rate sprayers. However, there is little research comparing variable- and constant-rate spray applications as crop characteristics change throughout a growing season. This study evaluated spray volume, spray quality (e.g., coverage and deposit density), and off-target spray losses of variable- and constant-rate sprayers across multiple phenophases in an apple ( Malus domestica ) orchard and a grape ( Vitis vinifera ) vineyard. The variable-rate sprayer mode applied 67% to 74% less volume in the orchard and 61% to 80% less volume in the vineyard. Spray coverage (percent), measured by water-sensitive cards (WSC), was consistently greater in the constant-rate mode compared with the variable-rate mode, but in many cases, excessive coverage (i.e., over-spray) was recorded. The variable-rate sprayer reduced off-target losses, measured by WSC coverage, up to 40% in the orchard and up to 33% in the vineyard. Spray application deposit densities (droplets per square centimeter) on target canopies were typically greater in variable-rate mode. However, the deposit densities were confounded in over-spray conditions because droplets coalesced on the WSC resulting in artificially low values (i.e., few, very large droplets). Spray efficiencies were most improved early in the growing season, when canopy density was lowest, demonstrating the importance of tailoring spray volume to plant canopy characteristics.