Cultural Management Practices Research Articles

Bermudagrass Freezing Tolerance Associated with Abscisic Acid Metabolism and Dehydrin Expression during Cold Acclimation

Recent advances in bermudagrass [Cynodon dactylon (L.) Pers. var. dactylon] breeding and cultural management practices have enabled its use as a sports surface in U.S. Department of Agriculture cold hardiness zones 5 and 6. Use of these more cold-hardy bermudagrass cultivars further into transition- and cool-season zones increases the probability of freezing injury and increases the need for an improved understanding of physiological responses to chilling and freezing temperatures. Abscisic acid (ABA) has been shown to increase during cold acclimation (CA) and play a role in dehydration tolerance. This study investigated changes in ABA metabolism and dehydrin expression during CA and their association with freezing tolerance in four bermudagrass cultivars. Two cold-tolerant (‘Patriot’ and ‘Riviera’) and two relatively cold-sensitive (‘Tifway’ and ‘Princess’) cultivars were either subjected to CA at 8 °C day/4 °C night with a light intensity of 250 μmol·m−2·s−1 over a 10-h photoperiod for 21 days or maintained at 28 °C day/24 °C night over a 12-h photoperiod. In a separate study, exogenous ABA at 0, 50, 100, and 150 μm was applied to ‘Patriot’ bermudagrass without CA. ABA content in leaf and stolon tissues increased substantially during the first week of CA and remained relatively stable thereafter. ‘Patriot’ and ‘Riviera’ had greater ABA content and less stolon electrolyte leakage (EL) relative to ‘Tifway’ and ‘Princess’. Expression of a 25 kDa dehydrin protein increased during CA in all four cultivars. A significant correlation was found between ABA content and freezing tolerance. Exogenously applying ABA to ‘Patriot’ at 50, 100, and 150 μm significantly increased endogenous ABA content and the 25 kDa dehydrin expression and reduced stolon EL. The results suggest that alteration of ABA metabolism during CA is closely associated with freezing tolerance. Selection and use of cultivars with substantial accumulation of ABA and certain dehydrins during CA or in response to exogenous ABA could improve bermudagrass persistence in transition zone climates.

Convergence and divergence issues in strategic management – Indonesia's experience with the Balanced Scorecard in HR management

Globalization pressures escalate competitiveness and, in response, global companies tend to adopt a handful of Western management practices. One of these is the Balanced Scorecard. However, empirical evidence assessing the transferability and effectiveness of Western best practices into Asian countries is scarce. In particular, empirical evidence relating to the effectiveness of Balanced Scorecard implementations is limited, as is the impact of Asian Balanced Scorecard contextual variables. This article contributes to this gap through the study of a Central Bank of Indonesia (BI) Balanced Scorecard implementation within a conceptual framework that explores convergence and divergence of global management practices. The lessons learned discuss how divergent factors such as national culture, leadership styles, organizational culture and human resource management practices can influence Asian context Balanced Scorecard implementations.

Production Practices for Satsuma Mandarins in the Southeastern United States

Satsuma mandarin is presently the primary citrus crop for citrus growers in south Alabama, south Mississippi, and for certain new plantings in northwest Florida. Current growth in satsuma mandarin hectarage in Alabama is similar to the historical hectarage expansion that occurred during decades or clusters of years with a low incidence of lethal, freezing temperatures. Commercial groves currently range in size from 100 to 2000 trees and use various freeze protection strategies, including wind breaks, overstory frost protection with pine or pecan trees, under-tree and scaffold branch irrigation, and high tunnel polyethylene-covered greenhouses. The various methods of freeze protection require adjustments in cultural management practices, including spacing, pruning, irrigation, and fertilization. The primary rootstock used and recommended for its cold-hardiness and edaphic adaptation is Poncirus trifoliata. Some groves use ‘Swingle’ citrumelo, mainly because it is grown and propagated in Louisiana, where it is valued for its higher salt tolerance. ‘Owari’ was the original cultivar introduced to the United States from Japan in the late 19th century and is still the main cultivar in Alabama today, although earlier maturing cultivars, including ‘Brown Select’, ‘Early St. Ann’, and ‘LA Early’, are being introduced to extend the marketing season. Cultivars from Japan and China, including ‘Okitsu Wase’, ‘Miyagawa Wase’, and ‘Xie Shan’, are currently being evaluated for suitability in the region. Three general methods of culture with regard to spacing and pruning are discussed. Nitrogen application rates are typically low to moderate, yet leaf nitrogen levels surveyed in groves in 2005 were generally optimal or high with respect to published sufficiency levels for mature citrus in Florida.

Back to the Future: Using traditional knowledge to strengthen biodiversity conservation on Pohnpei

Pohnpei’s traditional belief system strongly supports con- servation, but years of foreign rule and influence, popula- tion growth, excessive US aid, shift to a cash economy and other factors have combined to weaken the island- ers’ conservation ethic. The result has been a rapid de- cline in biodiversity health, which has in turn led to a de- crease in quality of life and increased dependence on out- side assistance. Conventional government-led western style approaches to resource management were clearly failing, and in 1990, The Nature Conservancy, the local government, and other partners embarked on a program to involve the island’s traditional leaders and other cultural experts in the protection of the island’s upland forest wa- tershed. After a difficult start, the program has focused on combining Pohnpei culture and traditional knowledge with modern conservation planning and management prac- tices with some success. The result has been a unique community-based management approach that establish- es local control over spatially discreet resources that are legitimately considered to belong to the community and the return of resource management and use to an auto- nomous, consensus-based decision-making process. In a sense, the approach is an act of reconciliation, reconfirm- ing those aspects of both political systems that are con- sidered legitimate. For the participants, it has been a valu- able learning experience through which a uniquely “Pohn- pei-style” approach - suited specifically to the island’s so- cial and political conditions - is being developed.

Apera spica‐venti population dynamics and impact on crop yield as affected by tillage, crop rotation, location and herbicide programmes

Summary Apera spica‐venti is a winter annual grass and, increasingly, a severe weed problem in autumn‐sown crops. Non‐inversion tillage has become more common in Denmark in recent years, but may accentuate problems with A. spica‐venti. These problems may be avoided, if selected preventive and cultural weed management practices are adopted. To this end, we conducted a 4‐year field study investigating the effects of crop rotation, tillage method, location and limited herbicide input on A. spica‐venti population dynamics and crop yield. Additionally, detailed studies were performed on the fate of A. spica‐venti seeds when incorporated to different soil depths. The location with a lighter soil texture, cooler climate and higher rainfall favoured A. spica‐venti growth and consequently crop yield loss, especially in the crop sequence comprised only of autumn‐sown crops and with non‐inversion tine tillage. Incorporating A. spica‐venti seeds in the soil improved their survival, explaining the higher A. spica‐venti proliferation seen with tine tillage as opposed to direct drilling. The rotations including an even mixture of spring‐ and autumn‐sown crops did not lead to noteworthy changes in the A. spica‐venti population, irrespective of tillage method. Thus, in many regions, management of A. spica‐venti will require rotations that balance autumn‐ and spring‐sown crops.

Effect of allelopathic rice varieties combined with cultural management options on paddy field weeds

A number of techniques, including cultural management, allelopathy and bioherbicide, have been considered as alternatives for synthetic herbicides, but successful weed control will require the careful integration of these multiple techniques. This study was conducted to assess the use of allelopathic rice varieties in combination with cultural management options on paddy weeds, in order to develop an allelopathy-based technique to reduce herbicide use in paddies. The weed-suppressive effects of the rice varieties tested varied highly with allelopathic trait, planting pattern and cultural management including planting density, flooding depth and duration and supply of nitrogen. Allelopathic rice varieties PI312777 and Huagan-1 demonstrated much stronger weed suppression than the non-allelopathic variety Huajianxian under the same planting pattern and cultural management. Their weed-suppressive effect was increased with cultural management options. In particular, if integrated cultural management options of allelopathic rice varieties included a low-dose (bensulfuron-methyl, 25 g AI ha(-1), a third of the recommended dose) herbicide application, the emergence and growth of most weeds found in paddy fields was completely controlled. No grain yield reduction for allelopathic varieties occurred under integrated cultural management options, whereas with the non-allelopathic variety a reduction of up to 45-60% was measurable even with the low-dose herbicide application. The allelopathic potential of rice varieties will likely have a great impact on paddy weed control if integrated with cultural management options and application of low doses of herbicides. Therefore, it is feasible to reduce herbicide input in paddies if allelopathic rice is grown under integrated cultural management practices.

Reduced Surface Runoff Losses of Metolachlor in Narrow‐Row Compared to Wide‐Row Soybean

Cultural management practices that reduce the off-site transport of herbicides applied to row crops are needed to protect surface water quality. A soybean [Glycine max (L.) Merr.] field study was conducted near Stoneville, MS on Sharkey clay to evaluate row spacing (50 cm vs. 100 cm) effects on metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(methoxy-1-methylethyl) acetamide] transport. One day after the foliar application of metolachlor to 2.03 m wide by 2.43 m long plots, 60 mm h(-1) of simulated rainfall was applied until 25 min of runoff was generated per plot. The calculated mass of metolachlor intercepted by the soybean foliage was greater in narrow-row than wide-row soybean, 0.39 kg ha(-1) vs. 0.23 kg ha(-1), respectively. Field and laboratory studies indicated that less than 2% of the metolachlor intercepted by the soybean foliage was available for foliar wash-off 1 d after application. Antecedent soil water content at the start of the simulations was lower in narrow-row soybean. In turn, there was a 1.7-fold greater time to runoff on narrow-row plots. The greater time to runoff likely contributed to lower metolachlor concentration in runoff from narrow-row plots. Cumulative metolachlor losses were significantly greater in wide-row than narrow-row soybean, 3.7% vs. 2.2%, respectively. Findings indicate that narrow-row planting systems may reduce metolachlor runoff following a post-emergence application.

Social and cultural dimensions of rodent pest management

Rice production in Vietnam is threatened by rodent pests, with a significant increase in impact reported from 1990 through to the early 21st century. Pre-harvest rice losses are typically 5-10%, with losses of >20% occurring in some years in some regions. Farmers' rodent control practices are generally reactive and rely essentially on chemical and physical methods. Ecologically-based rodent pest management (EBRM) was developed in the late 1990s to manage rodents in rice-based farming systems in Vietnam and other parts of South-East Asia. EBRM combines both cultural and physical rodent management practices such as synchrony of cropping, short 2-week rat campaigns at key periods in key habitats, increasing general hygiene around villages, and use of a community trap-barrier system. Although EBRM has been reported to be economically profitable, the successful adoption of this set of technologies requires community participation. In this paper we address issues relating to the adoption and sustainability of EBRM in lowland irrigated rice fields in the Mekong Delta in Vietnam. We particularly explore the social and cultural mechanisms involved in maintaining community participation to further understand the conditions under which EBRM works and does not work. Positive indications of sustained use of community-based EBRM include: a policy pronouncement from the prime minister directing the use of integrated rodent management; the use of existing cooperatives for developing community actions; budgetary allocation from provincial and local governments; diffusion of EBRM to provinces in the south and north that are not involved in farmer participatory field trials; and the adoption of EBRM by a non-governmental organization, World Vision Vietnam, in their area-development programs.

Cultural diversity, manning strategies and management practices in Greek shipping

The present paper examines the way Greek shipping companies and Greek seafarers perceive culture, and how this affects their approach to crew management and operation of the ships. The analysis focuses on the manning strategies employed by the companies, on the operational problems that might occur on-board, and on any possible disturbance of the relation between the ship, the office at shore and third parties. Finally, a number of management practices which, when implemented, help to overcome these problems is also examined. The research methodology includes a review of the existing literature and interviews conducted by means of questionnaires filled in by crew managers and seafarers. Results show that some of the predominant problems encountered aboard, as far as communication with multicultural crews is concerned, are rooted in cultural and linguistic incompatibility, as well as in inadequate and inappropriate training. Furthermore, crew managers and seafarers lack both a clear perception of culture, and share opinions on the implementation of manning strategies. The present paper concludes that culture management can enhance crew team cohesion, upgrade communication at all levels, and, finally, improve the quality of the working environment, the safety of the workplace and the overall performance of the team.

Use of plant growth regulators to increase polyphenolic compounds in the wild blueberry

With increasing awareness of the antioxidant properties of the wild blueberry (Vaccinium angustifolium Ait.), more emphasis has been placed on d eveloping cultural management practices to enhance fruit polyphenolic levels and the use of processing byproducts as potential polyphenolic sources for the nutraceutical market. Trials were initiated in 2004 and 2005, with four plant growth regulators (methyl jasmonate, abscisic acid, riboflavin and Retain®) applied to maturing berries of the select clone Fundy at the Wild Blueberry Research Centre (Debert, NS). Berries were harvested 3 wk after treatment applications, with collections of green leaf tissues at harvest and red leaf tissues two weeks after harvest in 2005. Assessment of polyphenolic and anthocyanin levels within the berry and leaf tissues followed the Folin-Ciocalteu and pH differential methods, respectively. Overall, substantially higher levels of polyphenolic compounds were found within the leaf tissues, although anthocyanin content was highest in the berries. The application of methyl jasmonate resulted in a minor elevation in levels of bioactives within the harvested berry and red leaf tissues. This increase in bioactives occurred, however, at the expense of harvestable yields, with lower yield in plots treated with methyl jasmonate in 2004. Results thus suggest that the use of some plant growth regulators (PGR) may serve to increase bioactives, but their value must be assessed against a possible yield reduction. In addition, these studies indicate that leaf debris may provide a superior polyphenolic source for the nutraceutical market. Key words: Wild blueberry, plant growth regulator, anthocyanins, polyphenolics

Double Pruning of Grapevines: A Cultural Practice to Reduce Infections byEutypa lata

Double pruning of grapevines was evaluated as a cultural management practice for reducing infections by <i>Eutypa lata</i> in spur-pruned vineyards. Double pruning involves two pruning passes through the vineyard. Vines are first prepruned by nonselectively trimming canes to a uniform height, generally 30 to 45 cm above spur positions, then pruned to traditional two-bud spurs in late winter when Eutypa infections are less likely to occur. In large vineyards, double pruning may allow for more final pruning in late winter, potentially reducing the number of infected spurs if Eutypa infections on prepruning wounds do not develop beyond the point where final pruning will occur. To evaluate double pruning, Chardonnay and Merlot grapevines were prepruned monthly from October to February with final pruning in March for three seasons. <i>Eutypa lata</i> spores were inoculated onto wounds at the time of prepruning in two seasons. Examination of inoculated canes after final pruning showed mean lengths of vascular discoloration below prepruning wounds of 0.29 to 4.67 cm in Chardonnay and 0.14 to 3.07 cm in Merlot, with maximum length of discoloration of 14 cm and 12 cm, respectively. Isolations for <i>E. lata</i> were made at various locations along the length of the discolored vascular tissue. <i>Eutypa lata</i> was not recovered from isolations made more than 4 cm below the point of inoculation, indicating that infections of prepruning wounds should all be eliminated during final pruning, as long as prepruning occurs 30 to 45 cm above the final pruning cuts. No impacts on viticultural performance were observed, including yield, pruning weight, and time of budbreak. By allowing for more final pruning to occur in March, double pruning should greatly reduce the number of Eutypa infections that occur each year.

Changes in kale (Brassica oleracea L. var. acephala) carotenoid and chlorophyll pigment concentrations during leaf ontogeny

Abstract There has been recent market interest in “baby” salad greens. However, little information exists on the nutritional differences between immature “baby” greens and produce traditionally sold at the fully mature stage. Kale ( Brassica oleracea L. var. acephala D.C.) contains high levels of lutein and β-carotene, which possess important human health properties. Kale was grown in a controlled environment and pigments were measured in young ( 4 weeks) leaves using high-performance liquid chromatography (HPLC). Significant differences were observed for all pigments during leaf development. Pigment accumulation followed a quadratic trend, with maximums occurring between the 1st and 3rd week of leaf age. The highest concentrations of lutein measured 15.1 mg/100 g fresh mass and occurred in 1–2 week old leaves. The remaining pigments reached maximum levels at 2–3 weeks (β-carotene at 11.6 mg/100 g; chlorophyll a at 251.4 mg/100 g; and chlorophyll b at 56.9 mg/100 g fresh mass). Mature fully expanded kale leaves accumulated higher carotenoid concentrations than immature or “baby” leaves, with senescent leaves having the lowest carotenoid concentrations. Harvesting kale leaves at a mature stage of development resulted in maximum carotenoid values. Cultural management practices that increase carotenoid concentrations would be expected to improve nutritional quality for fresh markets.

Management of soilborne diseases of potato

A large number of soilborne diseases that affect potato are important in the United States. In the Midwestern USA, early dying, involving Verticillium dahliae and Colletotrichum coccodes and the storage rots, pink rot and leak tuber rot, caused by Phytophthora erythroseptica and Pythium ultimum are among the most serious. Various aspects of the biology and aetiology of these pathogens have been investigated to improve our understanding of the factors involved in disease development. These studies have addressed knowledge gaps and have assisted in the development of management strategies and tactics for each disease. Disease management integrates cultural practices, use of agrochemicals and to some degree, host resistance. Unfortunately, cultural management practices alone are currently inadequate to control these diseases, causing the potato industry to become over-reliant on the use of agrochemicals for effective management. Current research efforts are directed at the identification and incorporation of genetic resistance into cultivars with acceptable horticultural characteristics to provide more effective disease management.

Planting Date and Nitrogen Effects on Fusarium Head Blight and Leaf Spotting Diseases in Spring Wheat

Cultural management practices play important roles in minimizing losses caused by Fusarium head blight (FHB) and leaf spotting diseases (leaf‐spot) in wheat (Triticum aestivum L.). A field experiment was conducted in Ottawa, Canada, for 3 yr (2003–2005) in two sites representing clay loam and sandy loam soils to examine the effects of planting date and N management on the incidence and severity of FHB and leaf‐spot {tan spot, Septoria leaf blotch and Stagonospora nodorum blotch) in spring wheat. The cultivar AC Brio was seeded at three dates at approximately 10‐d intervals starting in the last week of April. The five N treatments included 0, 60, and 100 kg N ha−1 applied as starter; 60 + 40 kg N ha−1 (starter + top‐dress at boot stage); and 60 + 40 kg N ha−1 (starter + foliar spray at boot stage). Generally, incidence of FHB and severity of leaf‐spot were greater in the heavy‐textured soil than in the light‐textured soil. Across site–year, the incidence of FHB ranged from 13 to 45%, and severity varied from 14 and 52%. On both soils, planting date had a consistently greater effect on the incidence and severity of FHB: the later the planting date beyond 9 May, the greater the incidence of FHB. The late‐planted wheat also had the greatest severity of leaf‐spot. Planting after 9 May also significantly reduced grain yield by 15 to 45%. Wheat grown without added N had the greatest incidence of FHB and leaf‐spot severities than that supplied with adequate N, especially in the heavy‐textured soil. The effect of N on FHB was not consistent over site–years, but leaf‐spot was significantly reduced with a starter application of N at 100 kg ha−1. Our data indicate that environmental variation induced by different planting dates or by different growing seasons and site appeared to have greater effects on FHB and leaf‐spot in wheat than N application. The results suggest that the incidence of FHB and severity of leaf‐spot in spring wheat can be minimized through early planting combined with adequate starter N application.

The Case of Trinity University

The case of Trinity University is an ideal way to introduce graduate students in educational leadership preparation programs to the university culture and how it shapes the graduate curriculum, faculty expectations for student outcomes, and professional socialization processes. Master’s and doctoral students who take courses related to cultural issues, organizational behavior and change, and management and administrative strategies will have an opportunity to discuss these same processes at the postsecondary level and note how they compare and contrast to the cultural and organizational environments in the public schools. What students experience in both worlds (K-12 and higher) can inform their knowledge of leadership, mission, management, and culture. This case encourages students to address cultural change and the effects it will have on leader preparation in terms of the “alignment between espoused cultural values and actual management practices... [and how it can]... improve organizational performance” (Smart &amp; St. John, 1996, p. 232).

(164) The Influence of Mulch Applications on Vegetation Dynamics in Organically Managed Highbush Blueberry

Within-row weed management of highbush blueberry (Vaccinium corymbosum L.) is reliant upon herbicide applications. However, in organic production, herbicides are typically not permitted and alternative methods must be used. The impact of thick (25-cm) mulch applications on weed pressure in an organic production system was initiated at a commercial operation in Nova Scotia, Canada, during 2005. A split-plot experimental design was used with five blocks (replications), six treatments, and five plants per split plot (cv. Duke). The whole-plot factor consisted of mulch/fertility treatments and included: i) control (no amendment); ii) ammonium sulphate fertilizer (30 kg·ha-1 N); iii) pelletized poultry manure (60 kg·ha-1 N); iv) pine needles (80 t·ha-1); v) horse manure and sawdust compost (550 t·ha-1); and vi) seafood waste compost (360 t·ha-1). The split-plot factor consisted of level of hand weeding (–/+). Weed control was assessed by sampling percent ground cover and weed shoot biomass in three 0.25-m2 quadrats in nonweeded subplots. Blueberry leaf N content, plant canopy volume, and berry yield (fresh weight and number) were recorded. The manure/sawdust compost and pine needle treatments had the lowest weed biomass and percent ground cover values, thereby providing the best weed control. Weed shoot biomass, blueberry leaf N, plant canopy volume, and berry yield were greatest in the seafood waste compost treatment. Results from this preliminary study indicate the potential of using these groundcover treatments to improve organic cultural management practices.

The Wicked Problem of Collaboration

The Wicked Problem of Collaboration

Cabbage Yield and Glucosinolate Concentrations as Affected by Nitrogen and Sulfur Fertility

Glucosinolates are a class of nitrogen (N) and sulfur (S) containing compounds shown to have cancer-preventing properties in animal models and widely found in cruciferous plants. The overall objective of this study was to determine whether N and S fertility affects glucosinolate concentrations in cabbage (Brassica oleracea L. Capitata group). Field studies on a sandy soil low in available N and S were conducted over a 2-year period with both green (`Grand Slam') and red (`Vorox') cabbage cultivars. Treatments evaluated each year were the interactive effects of N (125 and 250 kg·ha–1) and S (0, and 110 kg·ha–1) fertilizer application. Yield of both cabbage cultivars increased with increasing N and S in the second year of the study, but not in the first. Tissue N concentrations in heads at harvest increased with N application and tissue S concentrations increased with S application. When S was not applied, tissue S decreased significantly as N rate increased, while N rate had no effect on tissue S concentrations when S was applied. The dominant glucosinolate detected in both cabbage cultivars was glucobrassicin, with indole forms accounting for about 80% of the total glucosinolates regardless of treatment. Tissue N was negatively correlated and tissue S and S to N ratio were positively correlated with total glucosinolate concentration, although all correlations were generally weak (r2 &lt; 0.5). Total glucosinolates and glucobrassicin concentrations were maximized in both cultivars at the low N and high S application rates. Except for sinigrin in one of the 2 years, all glucosinolates detected were higher in Vorox than in `Grand Slam'. Based on these results, glucosinolates in cabbage can be manipulated by cultural management practices as well as genetics.

A Temperature Index Model to Estimate Long-term Freeze-risk of Satsuma Mandarins Grown on the Northern Coast of the Gulf of Mexico

Estimates of long-term freeze-risk aid decisions regarding crop, cultivar, and rootstock selection, cultural management practices that promote cold hardiness, and methods of freeze protection. Citrus cold hardiness is mostly a function of air temperature, but historical weather records typically contain only daily maximum (Tmax) and minimum (Tmin) air temperatures. A mathematical model was developed that used Tmax and Tmin to estimate air temperature every hour during the diurnal cycle; a cold-hardiness index (CHI500) was calculated by summing the hours ≤10°C for the 500 h before each day; and the CHI500 was regressed against critical temperatures (Tc) that cause injury. The CHI500 was calculated from a weather station located within 0.1 km of an experimental grove and in the middle of the satsuma mandarin (Citrus unshiu Marc.) industry in southern Alabama. Calculation of CHI500 was verified by regressing a predicted CHI500 using Tmax and Tmin, to a measured CHI500 calculated using air temperatures measured every hour for 4 winter seasons (1999-2003). Predicted CHI500 was linearly related to measured CHI500 (r2 = 0.982). However, the slope was a little low such that trees with a CHI500 = 400, near the maximum cold-hardiness level achieved in this study, had predicted Tc that was 0.5 °C lower than measured Tc. Predicted and measured Tc were similar for nonhardened trees (CHI500 = 0). The ability of predicted Tc to estimate freeze injury was determined in 18 winter seasons where freeze injury was recorded. During injurious freeze events, predicted Tc was higher than Tmin except for a freeze on 8 Mar. 1996. In some freezes where the difference in Tc and Tmin was &lt;0.5 °C there were no visible injury symptoms. Injury by the freeze on 8 Mar. 1996 was due, in part, to abnormally rapid deacclimation because of defoliation by an earlier freeze on 4-6 Feb. the same year. A freeze rating scale was developed that related the difference in Tc and Tmin to the extent of injury. Severe freezes were characterized by tree death (Tc - Tmin &gt; 3.0 °C), moderate freezes by foliage kill and some stem dieback (1.0 °C ≤ Tc - Tmin ≤ 3.0 °C), and slight freezes by slight to no visible leaf injury (Tc - Tmin &lt; 1.0 °C). The model was applied to Tmax and Tmin recorded daily from 1948 through 2004 to estimate long-term freeze-risk for economically damaging freezes (severe and moderate freeze ratings). Economically damaging freezes occurred 1 out of 4 years in the 56-year study, although 8 of the 14 freeze years occurred in two clusters, the first 5 years in the 1960s and 1980s. Potential modification of freeze-risk using within-tree microsprinkler irrigation and more cold-hardy cultivars was discussed.

Nutritional interactions influencing diseases of potato

Nutrient management can decrease the severity of a number of important potato diseases, and certain practices, such as maintaining a low pH for scab control, have been followed for that single objective. More commonly, growers have incorporated fertility modifications into their particular disease and farming situations. Unfortunately, disease minimization may or may not be consistent with optimal fertilization for yield, quality, and profitability. Optimization for one disease may not match that for another, and the exact mechanisms involved are often complex and poorly understood. Potato growers will continue to experience conflicting production constraints. These constraints include price-driven needs for yield improvement and expense reduction; customer-driven demands for quality improvement; varietal shifts driven by the above considerations rather than by disease reduction; increasing pressure to justify, shift and reduce pesticide use; continuing concerns about nitrogen and phosphorus movement in groundwater and runoff; and increased attention to management of rotation crops. On the positive side, nutrient management strategies for highly specific situations continue to improve and practices addressing nutrient and disease variability within fields are becoming more sophisticated. In this context, there are opportunities for cultural management practices that reduce disease pressure and reliance on chemical controls. To be effectively integrated into such specialized management systems, the mechanisms of these control measures and the conditions under which they are practical will need to be better understood. Likewise, disease responses to these tactics need to be better quantified to allow an adequate cost-benefit analysis. With mounting concerns about the effects of agricultural pesticides on food safety, farm workers, and the environment, management of plant-available nutrients may become practical approaches for disease suppression in the future.