Individual Growers Research Articles

Trends in Occurrence, Distribution, and Population Densities of Plant-Parasitic Nematodes in the Pacific Northwest of the United States from 2012 to 2016

The Pacific Northwest (PNW) of the United States (Idaho, Oregon, and Washington) is a diverse agricultural production area with over 400 different commodities grown in the region. Plant-parasitic nematodes are a constraint to the production of many of these commodities. Soil sample data from 2012 to 2016 were obtained from nematode diagnostic laboratories in the region to assess trends in occurrence, population densities, and distribution of plant-parasitic nematodes in the PNW. A total of 38,022 unique data points were analyzed. The number of plant-parasitic nematode samples processed in the PNW by diagnostic laboratories has significantly increased from 2012 to 2016. Fifteen genera of plant-parasitic nematodes were identified by diagnostic laboratories, with 86% of the samples in the PNW containing at least one plant-parasitic nematode genus. These laboratories provide a valuable service to agriculture in the PNW. Additionally, they serve as a rich source of information on plant-parasitic nematode distribution, occurrence, and abundance that, when analyzed, provides an empirical basis upon which to interpret individual grower reports and make management recommendations.

Economic Impact of Spotted Wing Drosophila (Diptera: Drosophilidae) Yield Loss on Minnesota Raspberry Farms: A Grower Survey

Abstract Minnesota was dubbed the ‘raspberry consumption capital of America’ in 2017 by wholesaler Driscoll’s, Inc. Local production of this high-demand fruit, however, is limited by the invasive pest, spotted wing Drosophila (Drosophila suzukii Matsumura, Diptera: Drosophilidae). Recent research to develop integrated pest management (IPM) programs for MN berry crops indicates that raspberry growers are particularly vulnerable to significant spotted wing Drosophila-related yield losses. Spotted wing Drosophila was detected in Minnesota in 2012 across 29 counties. This analysis explores the economic impact of raspberry yield losses associated with spotted wing Drosophila in Minnesota as part of a multifaceted research initiative. An electronic survey of 157 MN berry growers was conducted in November 2017. Eighty-two individual grower surveys were returned (52% response rate). The survey included questions about production acreage, marketing practices, spotted wing Drosophila-related yield losses and future production intentions. The results of the e-survey indicate that raspberry growers have borne the highest levels of infestation among MN fruit growers surveyed. Spotted wing Drosophila-related yield losses for raspberry growers ranged from 2 to 100% of planted acreage.The median yield loss for this group of growers was 20% in 2017. Applying the median yield loss to ex-ante production estimates, we conclude that MN growers lost approximately $2.36 million in raspberry sales during the 1 yr studied. Investing in spotted wing Drosophila control measures will help MN growers reduce some of these losses in the future.

Factors influencing long term tomato seed production under contract farming

Hybrid tomato seed production under contract farming in Northeast Thailand has been declining after three decades of initial introduction. However, some growers in some villages remain as long-term growers. This study was designed to identify factors influencing their long-term production decision making process. A purposive sampling technique was used to select the study sites and key informants for in-depth semi-structured interviews. Group interviews were conducted to validate the data. The contract hybrid tomato seed production system is a centralized model. It is based on a two-way contractual relationships between the company and the individual grower. The companies specify production systems and produce quality standards at a fixed time and price. They support a complete package of inputs credit, loans and extension services to the growers. Costs of all inputs and loans are deducted from the seed payment. These costs are usually forgiven when the crop fails through no fault of the growers. The growers cannot produce hybrid tomato seeds without a contract due to the proprietary germplasm. The quality of the product and marketing are also controlled by the companies. The companies must depend on the farmers’ knowledge however, for the management and technical skills. Therefore, the companies must allow considerable flexibility and leniency in enforcing the terms of the contracts. As a result, knowledgeable and skillful growers are vital factors in sustaining long term hybrid tomato seed production. Furthermore, grower’s personal characteristics stand out as an important factor for long term production. This is why the companies are lenient and flexible with the growers to sustain their mutual benefit.

Weed interference with no‐till soyabeans influenced by fine‐scale covariation between soil properties and cover crop performance

SummaryBalancing trade‐offs in conservation agriculture between the conflicting impacts of soil disturbance on crop yield and soil quality is complicated by the need for adequate weed management, especially in production systems with low, or no, reliance upon herbicides. Production of soyabeans no‐till planted into a rolled‐crimped cereal rye cover crop is attracting increasing farmer interest. Experimental work on this approach to date has provided inferences at the field scale and above, helping to identify broad recommendation domains for best management practices. For individual growers, however, fine‐scale information may also be helpful for making in‐field adjustments to refine the system. In a three‐year field study in Illinois, USA, we quantified key associations among no‐till soyabean performance in a rolled rye system and decametre‐scale variation in soil characteristics, cover crop performance and weed growth. Subfield variation in soil properties had both direct and indirect effects on soyabean yield. Local soil potassium limitation was linked to reduced rye height, which in turn indirectly reduced soyabean yields through decreased weed suppression by the cover crop. Slow‐draining field areas that were still moist at the time of cover crop termination were associated with lower soyabean stands, directly reducing yields. Although the subfield characteristics influencing soyabean and cover crop performance may vary from farm to farm, this study highlights potential gains to be realised in this production system from a better understanding of how such properties covary at fine spatial scales and taking steps to create an environment conducive to maximising cover crop establishment and growth.

Grower and regulator conflict in management of the citrus disease Huanglongbing in Brazil: A modelling study

Abstract In managing plant diseases, there is often tension between a regulator seeking to destroy infected plants to prevent further infection on a national scale and growers seeking to retain infected plants to continue obtaining yield. A high‐profile example is Huanglongbing (HLB) or citrus greening, a bacterial disease that threatens Brazil's citrus industry. To prevent the spread of HLB, especially from abandoned infected groves, the government regulated that if 28% of a plantation unit (grove) is found to be symptomatic, then the whole plantation unit must be destroyed. This decision used the best evidence available in 2008, which suggested that a 28% detectable prevalence corresponded with 100% actual prevalence, the disparity being due to asymptomatic infected trees and imperfect detection methods. Using a mathematical model with parameters estimated from field data, we evaluate the assumptions underlying the 28% threshold. We investigate the effects of spraying insecticide and removing diseased plants on the infectious pressure and potential loss of yield from an infected grove. We find that the relationship between detectable and actual prevalence is much wider than allowed for in the regulations. There is a high probability that groves with detectable levels of symptomatic plants substantially below 28% have a >90% prevalence of infected plants. Paradoxically, in a well‐managed orchard, the threshold of 28% may not be reached at 100% prevalence. Infectious pressure from an infected grove is substantially reduced when growers control disease. Individual growers failing to manage disease, therefore, threaten the wider grower community. Control is likely to increase yield and prolong grove productivity, but in some groves may reduce yield. Policy implications. Current disease thresholds aimed at restricting the spread of the citrus disease, Huanglongbing (HLB), in Brazil allow heavily infected groves to remain in the landscape, but lower thresholds would disadvantage growers who are already controlling disease. There is probably no threshold that is optimal for individual growers and regulators but roguing and spraying is beneficial to both parties. Regulations should focus less on prevalence thresholds, and instead encourage early detection and co‐ordinated spraying among growers to control Huanglongbing on a regional level.

Carbon footprinting of potato (Solanum tuberosum L.) production systems in Zimbabwe

Agriculture contributes significantly to the global greenhouse gas (GHG) emissions. Farmers need to fine-tune agricultural practices to balance the trade-offs between increasing productivity in order to feed a growing population and lowering GHG emissions to mitigate climate change and its impact on agriculture. We conducted a survey on the major cultural practices in four potato production systems in Zimbabwe, namely large-scale commercial, communal area, A1 and A2 resettlement production systems. The resettlement production systems were formed from the radical Fast Track Land Reform Programme initiated in 2000, which changed the landscape of commercial agriculture in Zimbabwe. We used survey data as an input into the ‘Cool Farm Tool – Potato’ model. The model calculates the contributions of various production operations to total GHG emission. Experienced growers were targeted. The average carbon footprint calculated was 251 kg CO2 eq./t potato harvested, ranging from 216 kg CO2 eq./t to 286 kg CO2 eq./t in the communal area and A2 resettlement production systems, respectively. The major drivers of the GHG emissions were fertilizer production and soil-related field emissions, which together accounted for on average 56% of the total emissions across all production systems. Although mitigation options were not assessed, the model outputs the factors/farm operations and their respective emission estimates allowing growers to choose the inputs and operations to reduce their carbon footprint. Opportunities for benchmarking as an incentive to improve performance exist given the large variation in GHG emission between individual growers.

Mathematical models are a powerful method to understand and control the spread of Huanglongbing.

Huanglongbing (HLB), or citrus greening, is a global citrus disease occurring in almost all citrus growing regions. It causes substantial economic burdens to individual growers, citrus industries and governments. Successful management strategies to reduce disease burden are desperately needed but with so many possible interventions and combinations thereof it is difficult to know which are worthwhile or cost-effective. We review how mathematical models have yielded useful insights into controlling disease spread for other vector-borne plant diseases, and the small number of mathematical models of HLB. We adapt a malaria model to HLB, by including temperature-dependent psyllid traits, “flushing” of trees, and economic costs, to show how models can be used to highlight the parameters that require more data collection or that should be targeted for intervention. We analyze the most common intervention strategy, insecticide spraying, to determine the most cost-effective spraying strategy. We find that fecundity and feeding rate of the vector require more experimental data collection, for wider temperatures ranges. Also, the best strategy for insecticide intervention is to spray for more days rather than pay extra for a more efficient spray. We conclude that mathematical models are able to provide useful recommendations for managing HLB spread.

Collaboration and Commitment in a Regional Supermarket Supply Chain

This article presents findings from a longitudinal case study of efforts by a 100-store regional grocery store chain to localize its supply of fresh produce. The study was conducted to better understand the development of collaborative supply chains between farmers and grocery stores, and the broader potential that grocery store chains might play in localizing food systems. Data consists of three years of the chain's local produce purchases via direct-store-delivery from farms to stores; a survey of store managers and farmer-vendors; and interviews with farmers and grocery store and chain-level management. Analysis is structured by a conceptual framework that links collaboration to trust, which undergirds mutual commitment and mutual dependency between supply chain members, and which is dependent upon effective communication and positive prior market exchanges. The study finds that organizational structures constraining single-store autonomy in purchasing and pricing, coupled with supply variability from farms, limits trust-building and the establishment of mutual commitments and dependencies. These constraints, however, do not completely exclude direct-store-delivery as a strategy for food system localization and grower market diversification. Practitioners can support the building of collaborative supply chains through capacity-building and shepherding of early market exchanges between growers and stores, and supporting individual growers or groups of growers to become preferred vendors for regional grocery chains. See the press release for this article.

What Is the Economic Benefit of a Citrus Health Management Area (CHMA)? A Case Study

A Citrus Health Management Area (CHMA) is a group of growers who work cooperatively to coordinate insecticide application timing and mode of action in order control the insect vector of citrus greening disease. CHMAs help prevent insect vectors from moving between groves and reduce the likelihood that insects will develop pesticide resistance. This 3-page fact sheet analyzes the case-study data on yields of Valencia oranges from blocks located in two different categories of CHMAs to find the impact of citrus greening disease on citrus yields and provide evidence on the effectiveness of best class CHMAs as a way to deal with the disease. The analysis provides evidence that CHMAs can enhance an individual grower’s profitability at a time when margins are becoming increasingly narrow. Written by Ariel Singerman and Brandon Page, and published by the Food and Resource Economics Department, February 2016. FE982/FE982: What Is the Economic Benefit of a Citrus Health Management Area (CHMA)? A Case Study (ufl.edu)

Moving science forward through: Meta‐analysis

Moving science <i>forward</i> through: Meta‐analysis

An overview of the recent approaches to terroir functional modelling, footprinting and zoning

Abstract. Notions of terroir and their conceptualization through agro-environmental sciences have become popular in many parts of world. Originally developed for wine, terroir now encompasses many other crops including fruits, vegetables, cheese, olive oil, coffee, cacao and other crops, linking the uniqueness and quality of both beverages and foods to the environment where they are produced, giving the consumer a sense of place. Climate, geology, geomorphology and soil are the main environmental factors which make up the terroir effect on different scales. Often considered immutable culturally, the natural components of terroir are actually a set of processes, which together create a delicate equilibrium and regulation of its effect on products in both space and time. Due to both a greater need to better understand regional-to-site variations in crop production and the growth in spatial analytic technologies, the study of terroir has shifted from a largely descriptive regional science to a more applied, technical research field. Furthermore, the explosion of spatial data availability and sensing technologies has made the within-field scale of study more valuable to the individual grower. The result has been greater adoption of these technologies but also issues associated with both the spatial and temporal scales required for practical applications, as well as the relevant approaches for data synthesis. Moreover, as soil microbial communities are known to be of vital importance for terrestrial processes by driving the major soil geochemical cycles and supporting healthy plant growth, an intensive investigation of the microbial organization and their function is also required. Our objective is to present an overview of existing data and modelling approaches for terroir functional modelling, footprinting and zoning on local and regional scales. This review will focus on two main areas of recent terroir research: (1) using new tools to unravel the biogeochemical cycles of both macro- and micronutrients, the biological and chemical signatures of terroirs (i.e. the metagenomic approach and regional fingerprinting); (2) terroir zoning on different scales: mapping terroirs and using remote- and proxy-sensing technologies to monitor soil quality and manage the crop system for better food quality. Both implementations of terroir chemical and biological footprinting and geospatial technologies are promising for the management of terroir units, particularly the remote and proxy data in conjunction with spatial statistics. Indeed, the managed zones will be updatable and the effects of viticultural and/or soil management practices might be easier to control. The prospect of facilitated terroir spatial monitoring makes it possible to address another great challenge in the years to come: the issue of terroir sustainability and the construction of efficient soil/viticultural management strategies that can be assessed and applied across numerous scales.

Apis sets record red clover seed: a climatic aberration

Western Oregon, USA is one of the better red clover seed-producing areas in the world, having an average yield of 676 kg/ha; individual growers report yields of over 1000 kg/ha. Bloom normally lasts from late June through to the third week in August in well-managed fields. From late June through the third week of July, Apis mellifera is the predominant pollinator. By early August, Apis is usually displaced by very large populations of workers and males of several species of Bombus, especially B. vosnesenskii Radoszkowski. However, 2009 was unique in that the last 16 days in July the max–mean temperature was 35.4 °C, with a max of 41.0 °C. Apis responded by changing its pollen collection in red clover from ±1% in previous years, to 41.5% during the 16 days of extreme heat, resulting in a yield of 1045 kg/ha in the first 30 days of red clover bloom. It is postulated that the extreme heat in that year reduced the turgidity of the clover floret and that the accompanying low humidity increased the sugar content of the nectar, making the floret more accessible and attractive. Reference is made to the parallels between high temperatures and Apis pollination of alfalfa in California, and our observations on red clover in Oregon.

Irrigated Agricultural Adaptation to Water and Climate Variability: The Economic Value of a Water Portfolio

AbstractIncreasing aridity, more frequent and intense drought, and greater degrees of water scarcity create unique challenges for agriculture. In response to these challenges, which often manifest themselves as lower and more variable surface water supplies, as well as depleted and degraded ground water supplies, growers tend to seek opportunities to adapt. One option for growers to reduce their exposure to water scarcity and heightened uncertainty is to diversify. Indeed, access to a portfolio of supplies is one way in which water and irrigation districts, as well as individual growers, are responding to the changing landscape of water resource availability. This article evaluates the benefits to irrigated agriculture from having access to multiple sources of water. With farm‐level information on 1,900 agricultural parcels across California, we use the hedonic property value method to investigate the extent that growers benefit from having access to multiple sources of water (i.e., a water portfolio). Our results suggest that while lower quality waters, less reliable water, and less water all negatively impact agricultural land values, holding a water portfolio has a positive impact on land values through its role in mitigating the negative aspects of these factors and reducing the sensitivity of agriculture to climate‐related factors. From a policy perspective, such results identify a valuable adaptation tool that irrigation districts may consider to help offset the negative impacts of climate change, drought, and population increases on water supply availability and reliability.

Factor analytic mixed models for the provision of grower information from national crop variety testing programs.

Key message Factor analytic mixed models for national crop variety testing programs have the potential to improve industry productivity through appropriate modelling and reporting to growers of variety by environment interaction. Crop variety testing programs are conducted in many countries world-wide. Within each program, data are combined across locations and seasons, and analysed in order to provide information to assist growers in choosing the best varieties for their conditions. Despite major advances in the statistical analysis of multi-environment trial data, such methodology has not been adopted within national variety testing programs. The most commonly used approach involves a variance component model that includes variety and environment main effects, and variety by environment (Vtimes E) interaction effects. The variety predictions obtained from such an analysis, and subsequently reported to growers, are typically on a long-term regional basis. In Australia, the variance component model has been found to be inadequate in terms of modelling Vtimes E interaction, and the reporting of information at a regional level often masks important local Vtimes E interaction. In contrast, the factor analytic mixed model approach that is widely used in Australian plant breeding programs, has regularly been found to provide a parsimonious and informative model for Vtimes E effects, and accurate predictions. In this paper we develop an approach for the analysis of crop variety evaluation data that is based on a factor analytic mixed model. The information obtained from such an analysis may well be superior, but will only enhance industry productivity if mechanisms exist for successful technology transfer. With this in mind, we offer a suggested reporting format that is user-friendly and contains far greater local information for individual growers than is currently the case.

First Report of Rice Leaf Spot by Alternaria gaisen from Pakistan.

A rice field owned by an individual grower in Lahore, Pakistan, was surveyed in July 2013. Plants with symptoms of black, circular, necrotic spots 3 to 4 mm in diameter and an average of 8 to 10 spots per leaf were observed. Diseased plants were present in the field either singly or in groups of three to five. Ten symptomatic plants were selected randomly, and one infected leaf per plant and one necrotic spot per leaf was selected for the isolation of the pathogen. Necrotic areas were cut into small pieces, surface sterilized with 1% sodium hypochlorite solution, and plated on 2% malt extract agar (MEA) (Sigma, Dorset, UK). After incubation at 25 ± 2°C for 4 to 5 days, fungal mycelium was transferred aseptically to fresh MEA for pure culture. Three different isolates grown for 7 days on MEA were selected for detailed morphological studies. The fungal colony was dark greenish-black, reaching 7 to 8 cm in diameter, with 2 to 3 poorly defined growth rings. Conidiophores were geniculate and 50 to 140 × 3 to 4.5 μm in size. Conidia were in chains of 4 to 10, ovoid, ranging in size from 35 to 50 × 8 to 10 μm, with 12 to 15 transversal and 0 to 2 longitudinal septa. Conidia darkened from dull tan yellow to brown as the culture aged. Based on morphological characteristics, the pathogen was identified as Alternaria gaisen (2). A pure culture of the pathogen was deposited in First Fungal Culture Bank of Pakistan (FCBP1354). Due to the complexity of morphology-based identification of the genus Alternaria, sequencing of the internal transcribed spacer (ITS) region was carried out using the ITS1/ITS4 primer pair (1,3). The nucleotide sequence (KJ806190) of an amplified DNA fragment was compared with those already submitted to GenBank. The BLAST results revealed 99% identity of our A. gaisen isolate to strains NW680 (EU520123.1), FC3s (JX391937.1), and CBS 632.93 (KC584197.1), as well as some other A. gaisen strains. Pathogenicity testing of the fungus was performed on Basmati-198, a common cultivar of rice in Pakistan, by either spraying leaves of 1-month-old plants with 10 ml of spore suspension (2 × 105 spores/ml) or mixing this spore suspension in soil at the time of sowing. Control plants were sprayed with sterilized water. Plants were kept in a glasshouse at 30 ± 2°C and monitored for disease development. After 15 days of incubation, similar leaf necrotic spots to those observed in the field, developed on all inoculated plants, whereas all control plants remained healthy and asympomatic. The experiment was repeated three times and similar results were obtained. Re-isolation of A. gaisen from the symptomatic leaves fulfilled Koch's pathogenicity postulate. Although limited to the field where it was observed, to our best of knowledge, this is the first report of rice leaf spot by A. gaisen from Pakistan. Also, rice has not been reported as the host of A. gaisen from any part of the world. This study indicates that A. gaisen is potentially an important pathogen of rice plants. Further investigations into epidemiology and disease management strategies for this new disease are warranted especially where rice crop is grown extensively.

Optimal Protein Segregation Strategies for Wheat Growers

A technology that can measure wheat grain protein concentration and then segregate grain based on measurements during harvesting is on the horizon. This new technology provides wheat growers with opportunities to segregate grain that can be directed to premium markets. In this article, we identify an individual grower's optimal segregation and blending strategies under non‐uniformly curved price schedules. When price schedules are three‐step shaped, we show that the optimal segregation and blending strategies can be obtained by solving a specified non‐linear programming problem. Based on cash price and protein distribution data for wheat in the U.S. Pacific Northwest region over 1991–2011, an application of our theoretical model shows that on average a Hard Red Winter (respectively, Hard Red Spring) wheat grower should be willing to pay about 17.7 (respectively, 30.8) cents for segregating one bushel of wheat. We also study how growers’ net returns would be affected were the technology to be adopted.

Integrating Social Science into Managing Herbicide-Resistant Weeds and Associated Environmental Impacts

Controlling herbicide resistance (HR) and its associated environmental risks is impossible without integrating social and economic science with biophysical and technology aspects. Herbicide resistance is a dynamically complex and ill-structured problem involving coupled natural–human systems that defy management approaches based on simple scientific and technology applications. The existence of mobile herbicide resistance and/or herbicide tolerance traits add complexity because susceptibility to the herbicide is a resource open to all farmers, impacting the weed population. Weed scientists have extensively researched the biophysical aspects and grower perceptions of HR. They also recognize that the “tragedy of the commons” can appear when herbicide resistance is mobile across farms. However, the human structures and processes, especially private and public institutions that influence individual and group decisions about HR, have received little analysis. To start filling that gap, we discuss an integrative management approach to sustainable weed control that addresses the social complexity of farm heterogeneity. For example, the need for a private or public collective mechanism becomes apparent to address common-pool resource (CPR) aspects when one farmer's weed control actions influence their neighbors' situations. In such conditions, sole reliance on education, technical assistance, and other incentives aimed at changing individual grower behavior likely will fail to stem the advance of HR. Social science theories can be used to enrich the understanding of human interaction with the biophysical environment and identify key actors and social change processes influencing those interactions in the case of HR. The short-run economic advantages of herbicides such as glyphosate work against social change to address HR, including the development of collective actions when mobile HR conditions exist. We discuss seven design principles that can improve the efficacy and cost of such collective approaches and draw insights from CPR approaches outside of HR.

Wine quality, reputation, denominations: How cooperatives and private wineries compete?

We analyze how cooperatives in Northern Italy (Alto Adige and Trentino) compete with private wineries regarding product quality and reputation, i.e. if firm organization affects wine quality and winery reputation. Moreover, we examine if cooperatives with deep roots in their local economy specialize in specific regional denomination rules (i.e. DOC, IGT). Compared to private wineries, cooperatives face additional challenges in order to raise wine quality, among them appropriate incentives that induce individual growers to supply high quality grapes (e.g. vineyard management and grape pricing schemes to lower yields). The quality reputation of a winery with consumers depends crucially on its winemaking skills. Wine regions differ with respect to climatic conditions and quality denomination rules. Assuming similar climatic conditions within wine regions as well as winemaking skills between firms, incentive schemes to induce individual growers to supply high quality grapes and quality denomination rules remain crucial determinants of wine quality and winery reputation when comparing different regions and firm organizational forms. The data set analyzed allows differentiating local cooperatives vs. private wineries and denotes retail prices, wine quality evaluations, indicators for winery reputation, and distinct denomination rules. We employ a hedonic pricing model in order to test the following hypothesis: First, wines produced by cooperatives suffer a significant reputation and/or wine quality discount relative to wines from private producers. Second, cooperatives and/or private wineries specialize in specific wine denominations for which they receive a price premium relative the competing organizational form. Our results are mixed. However, we reject the hypothesis that cooperatives suffer a reputation/wine quality discount relative to private producers for the Alto Adige wine region. Moreover, we find that regional cooperatives and private wineries specialize in specific wine denomination for which they receive a relative price premium (e.g. Alto Adige cooperatives specialize in DOC relative to private wineries in the region; private wineries in Trentino specialize in IGT denominated wines emphasizing their own brands). Our results indicate regional differences in terms of how cooperatives compete with private wineries with respect to wine quality and reputation. If cooperatives are able to implement incentive schemes to induce individual growers to raise grape quality, they may also gain a wine quality and reputation premium in the market. Specialization in local denomination rules allows private wineries and cooperatives to capture premium prices in different market segments.

Costs and Benefits of Implementing Sensor-controlled Irrigation in a Commercial Pot-in-Pot Container Nursery

Irrigation scheduling in ornamental plant production is complex due to the large number of species grown by individual growers and the need to consider plant, environment, and substrate conditions to make correct irrigation decisions on a daily or more frequent basis. The engineering team in our project has developed a smart wireless sensor node that is capable of integrating outputs from a range of soil moisture and environmental sensors to schedule irrigation events. In addition, an advanced monitoring and control software enables growers to manage irrigation based on set-point or model-based protocols, which are then independently executed by the nodes, enhancing or replacing human decision making. During 2012, we implemented a sensor-controlled vs. grower-controlled irrigation study at a pot-in-pot nursery in Tennessee. Sensor networks were installed in two separate production blocks of 3-year-old dogwood (Cornus florida ‘Cherokee Brave’) and 2-year-old red maple (Acer rubrum ‘Autumn Blaze’) trees grown in 15- and 30-gal containers, respectively. One row of trees in each block was irrigated based on the average reading of soil moisture sensors inserted in individual trees using micropulse irrigation, i.e., sensor controlled. Trees in the adjacent row and the rest of the block were independently irrigated by the grower using standard practices, i.e., grower controlled. Sensor volumetric water content (VWC) readings and irrigation volumes were logged by nodes on a 15-min basis and were relayed to a base station on the farm. For the study period between Mar. 2012 and Nov. 2012, average daily water applied by the grower-controlled irrigation to the dogwood block was 0.92 gal/tree, compared with 0.34 gal/tree applied using sensor-controlled irrigation; for red maple, these values were 1.72 gal/tree and 1.13 gal/tree, respectively. No significant differences in tree caliper or quality were noted between the two irrigation treatments in either species over the year. The cost of water for this particular operation was negligible consisting only of pumping costs, as water is drawn from a perennial stream with excellent water quality. Consequently, a conservative return on investment for a wireless sensor network capable of covering the entire operation was 37.5%, corresponding to a payback period of 2.7 years, associated almost entirely from a reduction in irrigation management time. Pricing in a nominal cost for water of $326 per acre-foot ($1 per 1000 gal) increased annualized net savings 9-fold, reducing the payback period to less than 4 months. This analysis did not factor in additional economic benefits such as reductions in production time, losses due to disease, or increased plant quality, which have been associated with the use of sensor-based irrigation control in other studies.

Evaluating the Potential Growth Advantage of Triploid Eastern Oysters (Crassostrea virginica) in South Carolina Relative to Commercially Cultured Diploid Native Stocks

This study represents the first evaluation of “naturally mated” triploid oysters in South Carolina (SC) waters in an attempt to create new business opportunities for the SC shellfish industry. Triploid eastern oysters, Crassostrea virginica, were grown alongside both a locally derived SC diploid line and an SC-Virginia (VA) diploid line at 6 commercial grow-out sites along the coast of South Carolina from August 2011 through March 2012. The triploid oyster line was created by fertilizing SC eggs with tetraploid VA sperm. The 2n SC-VA line was created by fertilizing SC eggs with VA diploid oyster sperm, and the 2n SC-SC line was created using both eggs and sperm from SC broodstock. The growth performance (shell height, biomass, and percent market size) of oysters was evaluated on commercial culture grounds, working in close cooperation with commercial fishermen. Oysters were deployed in various gear types, but conditions for growth among lines were standardized within sites. All grow-out sites had similar high salinity (>23 psu) and were established in shallow water (range, 0–6 ft, depending on tidal stage). Oysters were sampled frequently throughout the nursery period, 1mo after field deployment, and quarterly thereafter (data not presented) until an individual grower determined that at least 1 of the 3 oyster lines was ready to be harvested, at which time all 3 lines were sampled for the last time. At the final sampling, the mean shell height of the triploid oysters was significantly greater (P < 0.001) than at least 1 of the 2 diploid lines at all sites. Triploid ash-free dry tissue weights were found to be significantly greater (P < 0.001) than at least 1 of the diploid lines at all sites. The percent of market size oysters (shell height, >76 mm) was greater for the triploid oyster line than for either of the diploid lines at all sites except the Romain River site, where the use of a shellfish tumbler was applied during husbandry to address “overset.” One of the primary impediments to producing high-quality single oysters destined for the half-shell market is the unwanted fouling of the grow-out product, often by wild oyster spat resulting from naturally high levels of oyster recruitment, a phenomenon referred to as overset. The results of this study are important for the commercial shellfish industry in South Carolina through its demonstration that current triploid technology has the ability to create a quality oyster product, within a timeframe that avoids the intense period of oyster recruitment in the spring, following that of seed production, in the form of locally produced oysters for the lucrative, single, half-shell oyster market.