Row Cover Research Articles

Characteristics of muskmelon fruits in relation to temporary row cover and the number of fruits

ABSTRACT The muskmelon plants allow several ways to manipulate sources/drains ratio. The objective of this work was to evaluate characteristics of the productivity and quality of Cantaloupe melon fruits due to the temporary use of row cover and the number of fruits per plant. The experiment was carried out from August to December 2014, at Universidade Federal de Campina Grande (UFCG), Paraiba State, Brazil. The experimental design was randomized blocks with treatments allocated in split plots 5x3, with four replicates. The authors reported permanence time of the row cover at different times in the plot {20, 24, 28, 32, and 36 days after transplanting (DAT)} and, in the subplots, the number of fruits per plant (plants with one fruit, plants with two fruits and fruit-free setting plants). The authors evaluated traits of production and quality of fruits. The permanence time of row cover and number of fruits per plant promoted changes in the productivity and quality of the muskmelon fruits. The permanence of the row cover from 20 to 36 DAT provided reduction in the total soluble solids. The average fruit mass and fruit yield reached the maximum value with the permanence of the row cover up to 26.6 and 25.1 DAT, respectively. Plants with one and two fruits presented higher average fruit mass, but with lower productivity compared to the plant with fruit-free setting.

EFECTOS DEL USO DE MANTA TÉRMICA SOBRE VARIABLES AMBIENTALES Y RENDIMIENTO DE UN CULTIVO DE LECHUGA

El presente trabajo tuvo como objetivo evaluar el efecto de la protección de la manta térmica sobre el comportamiento de variables ambientales y el rendimiento de un cultivo de lechuga. Para ello, se sembró durante dos temporadas otoño-invernales un cultivar de lechuga tipo mantecosa (Lactuca sativa var. capitata) en bandejas de germinación de 128 celdas, con posterior trasplante en campo, realizado a los 37 días (ciclo 1) y 49 días (ciclo 2) después de la siembra. Los tratamientos fueron: 1) Cultivo protegido con manta térmica (MT); 2) Testigo no protegido (T) en un diseño experimental en parcelas divididas con tres repeticiones. El marco de plantación utilizado fue de 0,35 m entre hileras y 0,25 m entre plantas. El riego se efectuó mediante un sistema de goteo. Se evaluó el efecto de la manta térmica sobre la trasmisividad de la radiación fotosintéticamente activa (RFA), temperatura y humedad relativa del aire, rendimiento del cultivo, suma térmica en grados.día-1 desde el trasplante hasta la cosecha (ºC.ddt-1). Los resultados mostraron en el tratamiento MT una trasmisividad promedio de la RFA de 0,69 (ciclo 1) y 0,73 Mj.m-2.día-1 (ciclo 2), incremento de la temperatura del aire mínima, media y máxima en 1,1; 2,0 y 3,1 ºC, respectivamente, y de la humedad relativa. El rendimiento en peso fresco (t ha-1) presentó diferencias estadísticas significativas entre los tratamientos, siendo de: 37,7 (MT); 15,5 (T) para el ciclo 1 y 33,8 (MT) y 14,7 (T) para el ciclo 2. La suma térmica fue mayor en el tratamiento con manta térmica. La protección del cultivo permitió una mayor precocidad con mejoras significativas en el rendimiento.

Comparison of standard and organic pesticides as well as herbal products for control of insect pests of cabbage (Brassica oleracea) in Saskatchewan

Many insect pests can potentially damage cabbage (Brassica oleracea) grown in Saskatchewan. Root maggots (Delia spp), flea beetles (Phyllotreta spp) and cabbage worms (Order: Lepidoptera) are the main concerns. The objective of this project was to assess the potential to use of companion planted herbs or herbal essential oils as control methods for these pests. Standard synthetic pesticides were used as a check treatment. Organic pesticides and a row cover were also tested and compared to an untreated control. The herbal treatments were garlic or thyme plants interplanted with the cabbage crop along with foliar sprays of garlic or thyme oil. The pest control treatments were compared in trials using both transplanted and direct seeded cabbage. The standard and organic pesticide regimes both effectively controlled all three of the insect pests, and resulted in similar head yields in both the transplanted and direct seeded cabbage crops. The row cover successfully prevented insect damage but created problems with weed control and required extra materials and labour to construct. The microclimate created by the row cover decreased growth of the direct seeded crop. None of the herbal products provided effective control of any of the insect pests of cabbage. In conclusion, cabbage can be successfully grown in Saskatchewan with minimal losses to insects using either standard synthetic or organic pesticides, but the herbal were not effective in the form and rates tested in this project.

Horticultural Production Systems Influence Ground Beetle (Coleoptera: Carabidae) Distribution and Diversity in Cucurbits.

Commercial cucurbit production typically involves agriculturally intensive practices, with fields prepared using conventional tillage, plasticulture, and chemically based pest management. Conservation-based management options are limited. In this study, we consider two alternative strategies, strip tillage and the use of row covers. We compare their impact on the beneficial carabid beetle (Coleoptera: Carabidae) community in melons and squash, following conventional or organic systems, over two years. Multivariate analysis demonstrated that soil management system (strip tillage versus plasticulture) was the primary variable influencing carabid distribution; row cover was a less important factor. The response to soil management was species dependent. Some dominant species, such as Harpalus pensylvanicus DeGeer, demonstrated no preference for a particular soil treatment. For others, including the tiger beetle, Cicindela punctulata Olivier, and a slug predator, Chlaenius tricolor Dejean, activity-density was higher in strip-tillage production systems. Our analysis suggested that strip-tillage production systems support a richer, more diverse carabid community. These results demonstrate that even within intensive annual horticultural systems, production practices can play a critical role in shaping the beneficial arthropod community, potentially encouraging or limiting ecosystem services.

Optimising the duration of floating row cover period to minimise the incidence of tomato yellow leaf curl disease and maximise yield of tomato

The influence of polyester cover on tomato crops was evaluated to determine its effectiveness in reducing the incidence of tomato yellow leaf curl disease and on tomato yield. Uncovered plots were compared in a randomised block design with 14 treatments having different durations of cover. The identification of begomovirus was carried out by polymerase chain reaction, cloning and complete nucleotide sequencing of viruses from infected plants. Disease incidence was high in plots covered for less than 3 weeks with no significant differences among these treatments and those that were left uncovered. In the three treatments with the longest duration of cover, no disease was recorded but yield was significantly decreased. The optimum covering period was 6–7 weeks, providing protection against disease (10% incidence) and maintaining high yields (3 kg per plant). Floating row covers can play a major role in reducing begomovirus-induced diseases by reducing exposure to whiteflies which transmit these viruses. The current work appears to be the first attempt to optimise the cover period by sequentially removing covers from crops to analyse the consequences in terms of crop biomass, yield and disease and to explore the interactions between these parameters.

High Tunnel versus Climate-controlled Greenhouse: Transplant Time and Production Environment Impact Growth and Morphology of Cold-tolerant Bedding Plants

Commercial bedding plant production in northern latitudes often begins in late winter and continues through spring, when average outdoor temperatures require growers to actively heat their greenhouses (GHs). High tunnels (HTs) offer energy savings as they are passively heated and cooled structures that have a low initial cost. As a result, they have been used in northern latitudes to advance and extend the growing season and improve the quality of high-value horticultural crops. However, there is limited published information on growing bedding plants in HTs in northern latitudes. Our objectives were to quantify the effects of transplant date in an HT with or without a rowcover (RC) compared with a traditional heated GH on the growth and morphology of three cold-tolerant bedding plant species at two northern latitude locations, Purdue University (Purdue) and Cornell University (Cornell). Seedlings of snapdragon (Antirrhinum majus L. ‘Liberty Classic Yellow’), dianthus (Dianthus chinensis L. ‘Telstar Crimson’), and petunia (Petunia ×hybrida Vilm.-Andr. ‘Wave Pink’) were transplanted on weeks 13, 14, and 15 in 2012 (Purdue) and 2013 (both locations) and moved to either a glass-glazed GH or an HT without (HT) or with a rowcover (HT+RC). Several quality measurements increased when plants were grown in the HT compared with those grown in the GH. Dianthus and petunia transplanted at Purdue during week 13 in the HT and HT+RC were 33% and 47% shorter and had 51% and 31% more visible buds, respectively, compared with those grown in the GH. Similarly, petunia transplanted at Cornell during week 13 in the HT and HT+RC were 45% and 43% shorter, respectively, than their GH counterparts. The shoot dry mass of dianthus and snapdragon at Purdue was significantly higher when grown in the HT compared with the GH, regardless of transplant week or the use of RC likely because of increased daily light integral (DLI) in the HT environment. There was about a 1-week delay from transplant to first open flower for week 13 dianthus (at Purdue) and petunia (at both locations) when finished in the HT or HT+RC vs. their GH counterparts. Such a delay would be acceptable to growers who want to reduce the use of chemical growth regulators and heating costs. However, at both locations snapdragon transplanted on week 13 to the HT or HT+RC environments were delayed by 22 to 26 days compared with the GH. A delay of over 3 weeks could interfere with a grower’s production schedule, possibly making this crop unsuitable for production in northern latitude HTs.

Produção e qualidade de melão Cantaloupe em cultivo protegido temporariamente com agrotêxtil em Mossoró, Rio Grande do Norte

Desde o ano de 2001, na região do agropolo de Mossoró/Assu-RN, o agrotêxtil é utilizado como proteção de plantas contra pragas da cultura do meloeiro. Este experimento teve como objetivo avaliar a produção e a qualidade de dois híbridos de melão Cantaloupe, em cultivo protegido, temporariamente, com agrotêxtil. O trabalho foi realizado na Horta da Universidade Federal Rural do Semi-Árido (UFERSA), em Mossoró-RN, de julho a outubro de 2010. O delineamento experimental foi de blocos casualizados completos, com quatro repetições, dispostos no esquema de parcelas subdivididas no espaço. As parcelas foram representadas pelo número de dias após o transplante das mudas (DAT), em que as plantas permaneceram sob proteção de agrotêxtil (0; 18; 21; 24; 27 e 30 DAT) e, as subparcelas, por dois híbridos F1 de melão Cantaloupe: 'Acclaim' e 'Caribbean Gold RZ'. Foram avaliadas características de produção e de qualidade. Os tratamentos com proteção temporária com agrotêxtil não afetaram a produtividade total dos dois híbridos; todavia, a firmeza de polpa apresentou aumento crescente, enquanto a acidez total titulável, os açúcares solúveis totais, os sólidos solúveis e o pH apresentaram redução com o aumento do tempo de permanência do agrotêxtil sobre as plantas. O 'Caribbean Gold RZ', em comparação com o 'Acclaim', apresentou maior produtividade comercial para exportação, maior massa média de frutos, mais firmeza de polpa, maior acidez total titulável, maior teor de sólidos solúveis e menor pH.

Disease Severity on Cabbage Protected from Arthropod Pests with Insecticide Treated Agronets in Kenya

Cabbage (Brassica oleracea var. capitata L.) is one of the most important vegetables in Kenya, mainly grown by smallholder farmers for food and source of income. Its production is hampered by insect pests and diseases, leading to economic yield losses. Row cover insect proof nets have been used in the past to manage insect pests of cabbage and were recently introduced to Kenya. This study planned to document disease incidence and severity levels on cabbage grown under insecticide impregnated Agronets as a tool to manage insect pests and microclimate. The study was conducted at KALRO-Kabete and PTC (Practical Training Centre)-Thika, Kenya both at the nursery and in the field. Treatments included 1) use of insecticide (alpha cypermethrin) impregnated Agronets with (0.9 mm mesh), 2) untreated 0.4 mm mesh Agronet, 3) grass shading as a farmer practice (at nursery) and 4) control where there was no Agronet use. The treatments had five replications in a completely randomized block design. Plots measured 2 x 6 m, with a 1 m path between consecutive plots and 2 m between consecutive blocks. Three major diseases were recorded: damping off (Rhizoctonia solani), downy mildew (Peronospora parasitica) and black rot (Xanthomonas campestris pv. campestris). Treatments showed significant (P<0.05) differences on severity of damping off, which was lowest on seedlings covered with Agronets compared with the other treatments at nursery. Comparably, the downy mildew disease severity was higher on seedlings covered with Agronets than those with no cover or shading at the nursery. The findings show that frequent disease scouting is crucial when using Agronets for cabbage pests management. This would allow farmers to take action when diseases are noticed. Further supportive studies to understand threshold limits that can trigger growers to employ disease control application may be needed. (Resume d'auteur)

Combining Novel Modes of Action for Early-Season Management ofBemisia tabaci(Hemiptera: Aleyrodidae) and Tomato Yellow Leaf Curl Virus in Tomato

Management of Tomato yellow leaf curl virus (TYLCV) in Florida tomato involves destroying inoculum sources, using reflective mulches to repel the vector, growing TYLCV-tolerant varieties, and using insecticidal control. Three new insecticides with distinct modes of action were evaluated for management of Bemisia tabaci (Gennadius) and the whitefly-transmitted TYLCV. Chemicals were applied in paired combinations during the first 5 weeks after transplanting. Flupyradifurone (Sivanto) and cyantraniliprole (Cyazypyr™) are systemic insecticides that can be applied to soil or foliage and pyrifluquinazon is a translaminar material for foliar application. In order to determine optimal combination of chemicals with different modes of action for early-season whitefly control and virus suppression, systemic materials were soil-applied at-plant followed by foliar applications of a material with a distinct mode of action. Dinotefuran (Venom) was included as a standard at-plant material for comparison. Field trials were carried out using a split plot design with insecticide programs as main plot treatments which were split into plots covered under a floating row cover for the first 2 weeks after planting or left uncovered. The intention of the row cover treatment was to compare the degree of protection offered by at-plant treatments when the crop was exposed to virus immediately after transplanting to exposure two weeks after transplanting, and to determine if any at-plant treatment were comparable to mechanical exclusion of the vector. In fall 2012, when virus pressure was moderate, end of season virus incidence was lower than the untreated control in all chemical treatments except dinotefuran drench alone or followed by cyantraniliprole. Percentage virus in these 2 treatments were not significantly different from the untreated plots as of 5 weeks after transplanting in both fall trials (2012 and 2013). During both fall trials, percent virus was numerically lowest each week in either the flupyradifurone or flupyradifurone followed by pyrifluquinazon treatments, although the differences from other treatments were not always statistically significant. In spring 2013, when virus pressure was negligible, yield was higher in plots treated with dinotefuran followed by cyantraniliprole than in other treated plots, with the exception of flupyradifurone followed by cyantraniliprole. Row cover treatments were only partially successful, and did not indicate that any at-plant treatment was comparable to mechanical exclusion of the vector. Integration of new materials into insecticide recommendations and resistance management plans for Florida tomato (Solanum lycopersicum L.) production are discussed.

Cultivation of potato – use of plastic mulch and row covers on soil temperature, growth, nutrient status, and yield

Potato is one of the most important crops in the world because of its high nutritional value; however, traditional cultivation in bare soil may render low yields and poor quality. Crop production efficiency can be increased by using plastic mulching and row covers to modify root zone temperature and plant growth, in addition to reduction in pest damage and enhance production in cultivated plants. However, there is little information demonstrating the effect of row covers in combination with plastic mulch on potato. The aim of this study was to assess the change in root zone temperature and its effect on growth, leaf nutrient, and yield of potato using plastic mulch of different colors, in combination with row covers. Seed of cultivar Mondial was planted in May 2012. The study included four plastic films: black, white/black, silver/black, aluminum/black, and a control with bare soil, which were evaluated alone and in combination with row covers removed at 30 days after sowing in a split-plot design. Higher yields were obtained when no row cover (43.2 t ha−1) and the white/black film (42.2 t ha−1) were used. Leaf nitrogen, sulfur, and manganese concentration were higher in plants when row cover was used; in contrast, no–row cover plants were higher in Fe and Zn. Mulched plants were higher in Mn concentration than control plants. There was a quadratic relationship between mean soil temperature and total yield (R2 = 0.94), and between plant biomass and total yield (R2 = 0.98), between leaf area with total yield (R2 = 0.98).

부직포 터널 피복이 과채류의 초기생육 및 수량에 미치는 영향

부직포 터널 피복이 과채류의 초기생육 및 수량에 미치는 영향

Growth and yield of Cantaloupe melon 'Acclaim' in protected cultivation using agrotextile

In Rio Grande do Norte, the melon growers have been using the row cover on the roof of the plants to start flowering in order to reduce the population of insect pests that cause severe losses, rising production costs, especially with the application of defensive. Thus, it is important to know the best time to remove the row cover because, due to its use, it is assumed that there are changes in the physiological response of plants. In order to evaluate the growth and yield of the melon plants 'Acclaim' cultivated under protection agrotextile (TNT) for different periods, a trial was conducted at the Universidade Federal Rural do Semi-árido, Mossoró, Rio Grande do Norte state. The experimental design was a randomized complete block, with four replications, in a splitplot, the plots were the plant protection periods (0, 18, 21, 24, 27 and 30 days after transplanting, DAT), and splitplots, times of sampling the plants (13, 20, 27, 34, 41, 48 and 55 DAT). We evaluated the dry matter accumulation in leaves (LDMA), branches (BDMA), flowers (FDMA), fruits (FrdMA) and total (TDMA), assimilate partitioning, leaf area index (LAI), leaf weight ratio (LWR), absolute growth rate (AGR) and relative (RGR), net assimilation rate (NAR), total (PTOT) and marketable productivity (PCOM). The treatments with plant protection did not affect the TDMA which peaked at 295.12 g plant-1 at 53 DAT, with the fruits behaving like sink preferred plant, accounting for 72.25% of the dry mass accumulated. The LAI and the AGR grew by 55 and 42 DAT (1.95 and 18.518 g/plant/day), respectively, while the LWR and RGR decreased over the cycle, with peaks of 0.911 and 0.242 g/g/day, at 13 and 20 DAT, respectively. The PTOT and PCOM were not affected by periods of plant protection, with averages of 29.30 and 22.25 t ha-1, respectively, indicating that it is possible to manage the row cover in order to remove it later, that reduces costs and crop protection without significant loss in productivity.

Influence of Field Attack by Carrot Psyllid (Trioza apicalis Förster) on Sensory Quality, Antioxidant Capacity and Content of Terpenes, Falcarindiol and 6-Methoxymellein of Carrots (Daucus carota L.)

The effect of different degrees of attack by carrot psyllid (Trioza apicalis) on quality parameters of carrots was studied in field experiments for two years. Treatments were different degrees of physical insect protection by floating row cover. An increasing attack level of psyllids showed an enhancement effect on the antioxidant capacity (ORAC), content of falcarindiol, 6-methoxymellein, and terpenes, and scores for bitter taste, chemical flavor, terpene flavor, and toughness. Carrot psyllid attack decreased the yield, total sugar, fructose, glucose, and sensory attributes sweet taste, color hue, color strength, crispiness, and juiciness. Carrot plants at 8-10 weeks of age tolerated attack by psyllids at low levels (2% leaves with curling or discoloration).

Effect of mulching systems on fruit quality and phytochemical composition of newly developed strawberry lines

The effects of three mulching systems on total yield, average yield per plant, average fruit weight, soluble solids content (SSC), titratable acidity (TA), firmness and oxygen radical absorbance capacity (ORAC) of two newly developed lines (‘Orléans’ and ‘Saint Pierre’), one advanced selection (‘SJ8976-1’) and two commonly used cultivars (‘Jewel’ and ‘Kent’) were evaluated. The studied mulching systems were: plastic mulch (PM), mulch with row cover (PMRC), and matted-row system (MRS). Results showed that plastic mulch with row cover (PMRC) generally increased yield per plant, average fruit weight, SSC, firmness and ORAC, but differences varied within harvest times. No significant differences in total yield and TA were observed under the selected mulching systems. Both PMRC and PM accelerated the harvest periods compared to MRS. ‘Kent’ and ‘Jewel’ had the highest total yield while ‘SJ8976-1’ and ‘St-Pierre’ had the highest average fruit weight. The highest SSC, TA and ORAC were found in ‘Jewel’. There was no interaction between the mulching systems and genotypes, indicating that the effect of production system is independent of cultivars. PMRC seems to be a better growing system, improving fruit quality and increasing the nutritional value of all genotypes. By allowing off-season fruit production in cool climates, PMRC can be an alternative method to the costly high tunnels.

English

In the intensive horticulture,&nbsp;various ways of protected area are used for the growth of seedlings and the cultivation of vegetables in all seasons. The easiest and the cheapest form of protected area is agrotextile, which can be laid directly over vegetable crops (row cover). Agrotextiles are nonwovens which are manufactured from textile fibres which are usually of chemical origin. Textiles, used as agrotextiles require suitable tensile strength and good permeability characteristics with no significant deterioration under the influence of weather changes and UV radiation. Properties of agrotextiles depend on the fibres made of and on the type and conditions of production. The purpose of this study&nbsp;was to analyse the influence of simulated sun light radiation (xenon lamp) on physical properties of&nbsp;polypropylene (PP) nonwoven material,&nbsp;which is used for the production of agrotextiles.&nbsp;The research showed that the properties of row cover change when radiated with UV light. Tensile, tearing and bursting properties worsen after radiation and air permeability and water vapour show little increase. The changes in the properties are a consequence of changes in fibres,&nbsp;molecular and supermolecular structure which is exhibited in changed fibres and consequently also nonwoven properties. &nbsp; Key words:&nbsp;Agrotextile, polypropylene, nonwovens, UV radiation, properties.

Feasibility of Delaying Removal of Row Covers to Suppress Bacterial Wilt of Muskmelon (Cucumis melo).

Bacterial wilt, caused by Erwinia tracheiphila, is a major disease of cucurbit crops in the United States. Management of the disease relies on controlling two vector species, striped (Acalymma vittatum) and spotted (Diabrotica undecimpunctata) cucumber beetles. Six field trials were conducted at Iowa State University research farms during 2007, 2008, and 2009 to assess the efficacy of delayed removal of spunbond polypropylene row covers to control bacterial wilt on muskmelon (Cucumis melo). Treatments were (i) row cover removed at anthesis (conventional timing of removal), (ii) covers removed 10 days after row cover ends were opened at anthesis, (iii) covers removed 10 days after bumble bee hives were inserted under row covers at anthesis, and (iv) a noncovered control. In two field trials during 2007 and 2008, the delayed-removal row-cover treatments significantly suppressed bacterial wilt throughout the growing season and enhanced yield compared with the noncovered and removal-at-anthesis controls. In Gilbert in 2008, however, bacterial wilt suppression was equivalent among all three row-cover treatments. No bacterial wilt was observed during three trials in 2009, and there was minimal difference in marketable yield among treatments. Net returns were compared using partial budget and sensitivity analyses. Melon prices and occurrence of bacterial wilt had a strong impact on net returns. Using row covers increased production costs by 45%. In site years in which bacterial wilt occurred, delaying removal of row covers resulted in the highest returns. When bacterial wilt was absent, however, the delayed-removal row-cover treatments had the lowest returns. Results of the sensitivity analysis indicated that delaying removal of row covers for 10 days could be a cost-effective component of an integrated bacterial wilt suppression strategy for muskmelon where bacterial wilt occurs ≥50% of production seasons.

Horizontal Cane Orientation and Rowcover Application Improve Winter Survival and Yield of Trailing ‘Siskiyou’ Blackberry

Using the rotating cross-arm (RCA) trellis and cane training system, lateral canes of trailing ‘Siskiyou’ blackberry (genus Rubus subgenus Rubus) were kept vertically or rotated down to horizontal so that plant canopy was close to the ground. In winter, the plots were either covered with a non-woven rowcover (RC) or left uncovered. Cane injury was least in plants with lateral canes oriented horizontally and covered. Cane injury was high in plants with lateral canes oriented vertically in winter, whether covered or not, and among plants with lateral canes laid close to the ground but not covered. Among ‘Siskiyou’ plants that had lateral canes oriented horizontally, 280 flower clusters and 6.0 kg fruit/plant were produced on plants that had a RC in the winter compared with only 72 flower clusters and 1.7 kg fruit/plant for plants that were not covered in winter, in 2009. Fewer flower clusters developed and the yield was ≤2 kg/plant on plants with lateral canes oriented vertically. Yield differences between the most and least productive treatments were low in 2010 because of milder winter conditions and snowfall during the coldest periods that fully or partially covered the lateral canes oriented horizontally and close to the ground. The RC treatment had no effect on cane injury or yield when lateral canes were oriented vertically. The findings suggested that ‘Siskiyou’ blackberry can be grown in the eastern United States, where winter injury has frequently caused a crop failure, by positioning the lateral canes close to the ground and covering plants with a RC.

Potential Nitrogen Contributions from Legumes in Pacific Northwest Apple Orchards

As costs for nitrogenous fertilizers become increasingly expensive, organic and conventional apple producers recognize the potential to integrate leguminous plants in the orchard agro-ecosystem to contribute to N nutrition. We evaluated alfalfa as a drive row cover and white clover as an under tree living mulch. Both impacted nitrogen dynamics and tree performance. Alfalfa did not adversely affect tree growth and yield while potentially contributing to tree N nutrition. The white clover living mulch, clearly impacted soil nitrate and tree performance. Clover co-location with tree roots enabled N contribution from both tops and roots.

Respostas produtivas de alface em cultivo protegido com agrotêxtil

O trabalho foi realizado com o objetivo de avaliar a resposta produtiva de duas cultivares de alface (Vera e Lídia), em três ambientes de cultivo (sob agrotêxtil branco, sob agrotêxtil natural e em ambiente aberto), no inverno/primavera de 2005. Os materiais de agrotêxtil branco e natural, ambos de polipropileno, tinham 17 e 15 g m-2 de gramatura respectivamente. Utilizou-se o delineamento experimental de blocos casualizados, com os tratamentos dispostos em parcelas subdivididas, com quatro repetições. A testemunha foi constituída por parcela sem proteção das plantas com agrotêxtil (ambiente aberto). Foram avaliadas as produtividades total e comercial da cabeça, o número de folhas por cabeça, a porcentagem de folhas descartadas e o comprimento e a fitomassa seca do caule das plantas de alface. Para as características avaliadas verificou-se efeito significativo dos fatores de forma isolada. Embora não tenha sido constatada diferença significativa entre os tipos de agrotêxtil na produtividade, ambos os resultados com esses materiais foram superiores à testemunha, independentemente da cultivar. Para a época de inverno/primavera da região estudada, o uso de agrotêxtil de coloração branca ou natural é recomendável para as cultivares Vera e Lídia proporcionando aumento na biomassa fresca da cabeça comercial e melhor aproveitamento das folhas.

The Effects of Colored Plastic Mulches and Row Covers on the Growth and Yield of Okra

Okra (Abelmoschus esculentus ‘Clemson Spineless’) was grown on an Orangeburg sandy loam soil in Shorter, AL. Okra was direct-seeded in single rows. Treatments consisted of five mulch colors: black, white, red, silver, and blue installed either with or without spun-bonded row cover. Soil temperatures were 4 to 7 °C lower than air temperatures in all treatments. The use of darker (black, blue, red) -colored plastic mulches increased early and total yield of okra compared with bare soil with and without row cover. Increased soil and air temperatures did not always correlate to an increase in yield. It can be concluded that the use of dark plastic mulch is advantageous to growers of okra in climates that do not have cool springs, but the added use of row covers to plastic mulch has no effect on growth and yield. The profit of marketable okra produced using a row cover was $1.37 versus $1.35 per pound without a cover in 2003 and $1.28 versus $1.29 per pound in 2004. Blue plastic mulch is ≈$0.08 per foot more expensive than black plastic. Our data do not show an economic advantage for blue over black mulch for okra, but the positive effect cited by other authors may be more pronounced with leafy vegetables.