Influence Of Mulch Research Articles

Effect of organic mulches on the content of organic carbon in the soil

INTRODUCTION The content of organic carbon has long been recognized as a key component of soil quality (Reeves, 1997), and thus maintenance of soil organic carbon (SOC) in cropland soils is a major determinant of the productivity and long-term stability of agricultural systems (Carter, 2002). Soil organic matter (SOM) is composed of plant, animal, and microbial residues at varying stages of decomposition and amorphous humic substances (Jenkinson et al., 1992). An increase in the total content of SOC in organic farming was established by Marinari et al. (2010). Natural organic mulch eventually breaks down and becomes a part of the soil and a source of plant nutrients (Sharma et al., 1998; Bond & Grundy, 2001; Gruber et al., 2008). Increasing the amount of SOC is regarded as the main advantage of organic mulch (Paustian et al., 1997; Saroa & Lal, 2003). The influence of mulch on soil agrochemical properties depends on the chemical composition of mulch. It is recommended that in ecological farming soil should be covered with composts, chopped straw, and other organic residues to provide crops with nutrients, especially nitrogen (Relf, 2009). During the mineralization process of the mulch small amounts of nutrients become available for plants. However, it is not a sufficient supply of plant nutrients. Organic mulch is a source of nutrients for soil microorganisms, and as a result of their activity organic residues used for mulching are decomposed to available plant nutrients and a very important substance in soil--humus (Blanchart et al., 2006). Different opinions on the influence of organic mulches on SOM exist. A significant increase of SOC was observed in plots mulched with organic mulches (Relf, 2009). However, Kukkonen et al. (2004) stated that peat mulch has no significant influence on the amount of SOC. Oats and vetch grown for green manure and sprayed on soil surface were found to increase the amount of SOC and nitrogen in the soil compared with green manure inserted into the soil (Yadav, 1995; Astier et al., 2006). Cadavid et al. (1998) registered an increase of SOC and a decrease of the soil pH in plots covered with grass mulch. According to Blanco-Canqui & Lal (2007), mulching with straw during 10 years increased SOC by 33%. This means that 2/3 of the applied wheat straw was not converted into SOC and most probably was lost as emissions of C[O.sub.2] and C[H.sub.4]. Mulching even has the potential of reducing greenhouse gas emissions from soil by increasing its SOM content (Mulumba & Lal, 2008; Jordan et al., 2010). Our hypothesis was that the influence of organic mulch of different chemical composition on SOC will be unequal. The aim of the investigation was to evaluate the effect of various organic mulches and different thicknesses of the mulch layer on the SOC content. MATERIALS AND METHODS The two-factor field experiment was carried out in the Pomological Garden of Aleksandras Stulginskis University (formerly Lithuanian University of Agriculture) on a certified organic field (54[degrees]53'N, 23[degrees]50'E) in 2004-2011. The soil type of the experimental field is Calc(ar)i-Endohypogleyic Luvisol; its texture is medium clay loams on heavy clay loams and clays. Soil agrochemical characteristics are the following: [pH.sub.KCl] 6.4-6.7, the content of total nitrogen 0.119-0.142%, organic carbon 1.56-3.13%, available phosphorus 219.7-234.9 mg [kg.sup.-1], and potassium 134.3-180.5 mg [kg.sup.-1]. The sum of active temperatures (>10[degrees]C) in Lithuania is about 2100-2200[degrees]C, rainfall about 550-840 mm per year. The following treatments were used in the experiment: factor A--mulch: (1) without mulch, (2) straw, (3) peat, (4) sawdust, and (5) grass; factor B--thickness of the mulch layer: (1) 5 cm and (2) 10 cm. The direct influence of organic mulches was investigated in 2004-2009, and their residual effect in 2010-2011. …

Influence of mulching and irrigation level on water-use efficiency, plant growth and quality of strawberry (Fragaria ananassa)

Strawberry (Fragaria × ananassa Duch) cv. Chandler was grown in the field to investigate the effectiveness of different mulches and irrigation level on plant growth, fruit growth, yield and other quality parameters. I1 favoured plant growth, enhanced flowering (67.5 days), resulted in production of significantly larger fruit and higher yield (175.15 g/ plant), higher TSS, and ascorbic acid content with lesser incidence of albinism (17.9%) and botrytis rot than other irrigation levels. Plants mulched with BPM have significantly better growth, flowered and fruited early, produced larger fruit and higher yield, with slightly higher incidence of albinism (19.8%), but with lower incidence of botrytis rot (14.9 %) than those mulched with other materials. Irrigation level × mulching interaction has significantly influenced growth parameters like, crown height, plant spread and leaf area with I1 × M1 interaction. Strawberry produced larger fruit (13.1 g) and higher yield (185.8 g/plant), higher TSS, and higher ascorbic acid content with a slightly higher incidence of albinism, but comparatively lower incidence of botrytis rot under irrigation regime of I1 mulched with black polyethylene.

Survival and Growth of Callicarpa americana (American Beautyberry) of Northern and Southern Origin in USDA Hardiness Zones 5 and 6

Abstract Our objective was to determine whether provenance of origin and use of organic mulch influence survival, vegetative growth, and the number and size of fruit of Callicarpa americana L. (American beautyberry) planted north of its natural distribution in the central United States. Forty-eight plants were established in 2006 at each of four locations north of the natural distribution, two in Missouri and two in Iowa, and at one location within the natural distribution in Arkansas. Plants at each location (24 per provenance) were propagated from seeds collected from plants indigenous to southern Missouri and central Florida. Use of organic mulch increased percentage survival at two of four sites north of the natural distribution after Winter 2006–2007 and across all four northern locations after Winter 2007–2008. Survival of plants from the two origins was similar after Winter 2007–2008. Plants from Florida grew taller than plants from Missouri at the two planting locations in Missouri during the 2007 growing season. Development of fruit was poor in Iowa and was greatest on plants from Florida installed in southern Missouri and on plants from Missouri installed in central Missouri. Survival after Winter 2007–2008 was reduced to an average of 47% at the two sites in Iowa, and, across all sites, more plants from Missouri survived than plants from Florida. Plants within the natural distribution in Arkansas were 68% taller and had clusters of fruit 31% larger in late 2008 than plants at the closest site north of the natural distribution. We conclude American beautyberry can survive when planted in areas with winters colder than those where the species occurs naturally, and that plants from a northern provenance (Missouri) possess a greater capacity to survive than plants from Florida when planted north of the natural distribution in the Upper Midwest. Although the genetic potential for growth and displays of fruit is not manifest north of the species' natural limit, American beautyberry can be an attractive addition to landscapes in United States Department of Agriculture (USDA) hardiness zones as cold as zone 5b, where plants from a northern origin that are mulched during winter should be used.

Influence of Nitrogen Fertilization of Cabbage Grown in Mulches of Winter Cover Crops on Reducing the Population of the Cabbage Aphid (Brevicoryne brassicae L.)

Influence of Nitrogen Fertilization of Cabbage Grown in Mulches of Winter Cover Crops on Reducing the Population of the Cabbage Aphid (Brevicoryne brassicae L.) In 2003-2004, the influence of mulches of winter cover crops on the population of the cabbage aphid (Brevicoryne brassicae L.) in white cabbage production with two levels of N fertilization was investigated. Winter cover crops (rye, hairy vetch and their mixture) reduced B. brassicae population on cabbage by 86.1% to 100%. The level of nitrogen fertilization of cabbage had no effect on the aphid population. In addition, it was found that higher levels of nitrogen fertilization can cause an increase in the population of B. brassicae when cabbage is grown in bare soil.

Drip irrigation and black polyethylene mulch influence on growth, yield and water-use efficiency of tomato

A two year field study was conducted during 2001-2002 and 2002-2003 on sandy loam soil to investigate the effect of drip irrigation and black polyethylene mulch compared with surface irrigation, on growth, yield, water-use efficiency and economics of tomato (Lycopersicon esculentum Miller.). Drip irrigation at 80% evapo-transpiration (ET) crop based on pan evaporation applied gave significantly higher fruit yield (45.57 tonnes/ha) compared with the surface irrigation (29.43 tonnes/ha). Use of black polyethylene mulch plus drip irrigation further raised the fruit yield to 57.87 tonnes/ha. Plant height, leaf area index, dry matter production, fruit weight and yield increased significantly with the use of drip irrigation alone and in conjunction with polyethylene mulch compared to surface irrigation alone or with mulch. Water-use efficiency under drip irrigation alone, drip irrigation with polyethylene mulch and surface irrigation was 0.97, 1.23 and 0.42 tonne/ha-cm, respectively. Among different irrigation levels, drip irrigation at 80% ET resulted in higher net returns (34431 Rs/ha) and benefit cost ratio (1.76) in tomato. However, maximum net returns (51386 Rs/ha) and benefit cost ratio (2.03) was found with drip irrigation at 80% ET coupled with polyethylene mulch compared to other treatments. Drip irrigation besides giving a saving of 38% water resulted into 55% higher fruit yield compared to surface irrigation. Key words: Drip irrigation, pan evaporation, black polyethylene, fruit yield, tomato

The Influence of Mulching on the Maintenance of Seedlings on Degraded Land by Superficial Erosion

In order to establish the influence of soil mulching on the maintenance of seedlings planted on degraded lands by superficial erosion we used as mulching materials carton, litter and straw. The species subjected to the experiment were: black pine, honey locust, willow tree (oleaster) and sallow thorn.

Effect of mulching and fertilization on the quality of strawberries

A large part of the research carried out with strawberries (Fragaria × ananassa) has been with the aim of gaining higher yields. At the same time postharvest losses are remarkable. Therefore the need for research with the aim of increasing quality is rising. The aim of the present research was to study the influence of mulch (plastic and straw), fertilization and the age of plants (two, three and four years) on the quality of strawberry fruits. Experiments were carried out with cultivar Bounty during 2000–2002 at the Estonian Agricultural University. Results showed that fertilization had a positive effect on the yield of first grade fruits with both mulches. With plastic mulch, fertilization had a positive influence on vitamin C content. With straw mulch, fertilization decreased fruit damage. None of the experimental factors had an impact on the content of soluble solids. We concluded that injecting fertilizer solution into the soil under plastic mulch is an effective and inexpensive way to avoid a decrease in fruit size in the third year of production. Vitamin C content was negatively influenced by plant age, and in the three-year-old plantation, smaller fruits contained more vitamin C than larger fruits.;

SIMULATED EFFECTS OF REFLECTIVE MULCH ON ENERGY AND WATER CONSERVATION IN SEMI-ARID CENTRAL CALIFORNIA GREENHOUSES

Abstract In addition to the labor, energy and water consumption are the two main cost drivers in current greenhouse systems. Consequently, considerable effort is expended to conserve energy and water, and look for alternative energy sources. Greenhouses in hot and arid regions also require large quantities of water for irrigation. Proper environmental management systems can significantly change the energy and moisture dynamics of greenhouse production systems. This study aims to focus on reducing energy and water consumption in semi-arid California greenhouses. Influences of mulch (having different reflectivities) on energy and water conservation were investigated. The reflectivity of mulch used as a floor cover affects the radiation distribution within the canopy stand, eventually affecting the overall energy and water consumption. A dynamic computer simulation model was used to compare different mulch reflectivities, plant heights, and leaf dimensions to draw a conclusion about energy and water conservation. The results showed that using mulch with less reflectivity (for instance, 20% instead of 80%) reduced energy consumption by as much as 4.2%. With a decrease in reflectivity, the absorptivity of the mulch increases consequently. A high absorptivity results in higher rates of solar energy being absorbed during the day, and released during the night. The mulch functions as a collection device, while the floor itself being the thermal mass. By increasing the reflectivity from 20% to 80%, water savings of up to 8.6% occurred. The savings in energy consumption, therefore, always have to be seen in conjunction with the water consumption. Also, the effect of reflective mulch fades away as shade from canopy stand increases. A complete system analysis is necessary to obtain a complete energy and water balance and to be able to make a viable conclusion.

Black Vine Weevil (Coleoptera: Curculionidae) Performance in Container- and Field-Grown Hosts

The black vine weevil (Otiorhynchus sulcatus F.) feeds on a variety of plant species and is a serious pest of ornamental nursery crops. The larval stage has a more restricted diet than the adult stage, but the larvae are more damaging because they feed on roots and often stunt or kill their hosts. Performance and establishment of larvae in various container- and field-grown nursery crops were examined. In trials on containerized plants, adult black vine weevil were caged with various combinations of known larval hosts. In these trials, most larvae were found in Sedum and Heuchera versus Astilbe, redbud, and Taxus. Larvae collected from Sedum weighed significantly more than those from Heuchera or Taxus. In one field trial, adult black vine weevils were released, and establishment of larvae among potential hosts was examined. In this trial, Sedum was a better host than hemlock or Rudbeckia. Based on the numbers of larvae found in the different plant species, Sedum was the best host for larvae. Another field trial examined the influence of mulch on the occurrence of larvae. The presence of mulch around small field-grown Taxus plants did not increase the numbers of larvae compared with bare soil. The presence of aged pine bark or Taxus needle mulches did not influence the occurrence of black vine weevils in field plots of young Taxus. Data from monitoring adults suggest they either emigrated from these plots within several weeks of emergence, although suitable hosts were present, or there was high mortality.

Effects of ground cover (straw and compost) on the abundance of natural enemies and soil macro invertebrates in vineyards

Abstract1 Herbicides are commonly applied under grapevines in Australia to remove weeds and thereby to avoid water loss through transpiration.2 Interest in sustainability promotes a reduction in chemical inputs, including herbicides, leading to trials with surface mulches to suppress weeds.3 Surface mulches may also influence the abundance of a range of invertebrates. Potentially, an increase in natural enemies will contribute to pest control and encourage a reduction in pesticide application.4 We used three trapping methods and direct soil sampling to assess invertebrates at ground level, in the canopy and in the soil to determine the influence of mulch on natural enemies, potential pests and soil macroinvertebrates, including earthworms.5 Collections sorted to family demonstrated that the addition of straw or compost mulches increased natural enemies collected with pitfall traps and soil organisms. However, there was no clear indication of the overall superiority of either mulch.6 Abundance of ground beetles, parasitoid Hymenoptera and spiders collected with pitfall traps were increased by the addition of mulches. In the canopy, predatory and parasitic Diptera and predatory Hemiptera increased after mulching.7 Earthworms collected by hand sorting soil increased with straw mulching.8 No influence on pests was detected. Although Lepidoptera and Sigmurethra, collected in pitfall traps, increased with straw mulching, neither included pest species.9 The results are discussed with reference to the potential economic impact of mulches.

Cover Crops and Natural Vegetation Mulch Effect Achieved by Mechanical Management with Lateral Rotary Mower in Weed Population Dynamics in Citrus

The aim of this study was to obtain information on practical weed management in order to reduce the use of herbicides thereby contributing to the sustainable development of citrus crop. The experiment was carried out under field conditions at the experimental area of the Department of Vegetal Production at the College of Agriculture “Luiz de Queiroz,” Piracicaba, SP, Brazil, during the season 2002–2003. Influence of mulches produced by four types of vegetations on the dynamic population of weeds in the line of citrus crop (Citrus sinensis (L.) Osbeck) was evaluated. The experimental design was of factorial randomized blocks (4 {×} 2), where the treatments were: (i) four types of vegetation: Dolichos lablab L., Cajanus cajan (L.) Millsp, Penisetum glaucum (L.) Leeke, and the natural infestation composed basically by Panicum maximum Jacq.; and (ii) two types of fertilization: directed under canopy and broadcast. Mechanical management of the different vegetations was accomplished using a lateral rotary mower, KAMAQ, I model NINJA MAC 260, projected to release the green cut material under crop canopy, forming a mulch layer. The studied parameters were: (i) counting of weeds per m2 in the crop line after 30, 60, 90, 180, and 210 days following the cutting of existing vegetation; (ii) percentage of covered area by weeds; and (iii) some chemical properties of the soil. It was observed that the natural infestation showed a better weed control when compared with the other treatments, and that the broadcast fertilization, regardless of coverage used, presented a lower number of weeds.

Influence of mulch and soil compaction on earthworm cast properties

The effects of different mulch materials applied to compacted and uncompacted soil on the quantity and the quality of deposited earthworm casts were investigated. Biochemical properties and water stability of soil aggregates were compared with the corresponding properties of worm casts. This short-time experiment was conducted in the laboratory, simulating field conditions of mulch management in temperate agricultural systems. In microcosms Lumbricus terrestris and Octolasion cyaneum were inoculated separately. Barley, lupin, maize, or sugar-beet as straw or leaves were applied as mulch in amounts comparable to those usually found in the field. The soil was compacted artificially to a bulk density of 1.0 or 1.5 Mg m −3. In general, plant material and to a lesser extent soil compaction influenced the dynamic processes in the soil affecting microbial activity and water stable aggregation. Higher values of phosphatase activity was measured in compacted soil, while the corresponding enzyme activities in the casts were less affected by compaction. The worm species and the nutritional quality of the food source were factors strongly influencing water stable aggregation. Mulch as well as soil compaction had consequences for the burrowing activity of the worms, which resulted in different rates of cast production depending on the species.

Influence of Mulches on the Colonization by Adults and Survival of Larvae of the Colorado Potato Beetle (Coleoptera: Chrysomelidae) in Eggplant

Six treatments (no mulch, black plastic mulch, black plastic painted with reflective aluminum paint, straw mulch, black plastic plus straw, and a living mulch of rye growing between the rows) were used to grow eggplant and to observe the effects on movement of adult Colorado potato beetles, Leptinotarsa decemlineata (Say); oviposition; and density and survival of larvae. Straw mulch and rye treatments reduced movement of overwintered beetles into the plots and also reduced the growth of the plants compared to black plastic mulch. Survival from the egg to small larva (first and second instar) was lower in the plots with straw mulch and black plastic plus straw than in plots with rye, bare ground or aluminum-painted mulch. None of the treatments had an effect on movement of the first generation adults, which was primarily determined by the proximity of the plots to the source field of potatoes. It may be possible to combine the positive effects of black plastic on early season growth and straw mulch on reducing the survival of potato beetle larvae by transplanting the eggplants into black plastic mulch, then adding straw as the egg masses of the potato beetle begin to hatch.

The Effect of Plastic Mulch Color on Growth and Development of Cucumber and the Response of Cucumber Beetles to Mulch Color

Field experiments were performed to verify the influence of polyethylene mulches (red, blue, gray, black, and yellow) on the development and yield of two varieties of cucumber (Cucumis sativus), a hybrid, `Turbo' and an open-pollinated, `Marketmore 76'. The influence of the mulches on the population dynamics of the adult striped cucumber beetle (Acalymma vittatum) was also observed. Rhizosphere temperature, reflected surface temperatures, reflected wavelength, vine length, leaf number, leaf area, total fruit produced, and number of marketable fruit were some of the characteristics measured. A split plot experiment in a randomized blocks design with three replications was used. In relation to plant growth and yield, plants grown on red mulch showed the best growth and yield overall compared to blue, gray, black, and yellow colored mulches, The incidence of the cucumber beetles was highest in the yellow colored mulch. The `Turbo' variety had the highest fruit number in almost all of the colors of mulch compared to the open pollinated `Marketmore'. It is suggested that the differential growth and development of cucumbers was influenced by the rhizosphere temperature as well as the light spectrum reflected from the plastic. The response of the beetles to the mulch was mainly attributed to the different wavelengths reflected from the various mulches.

Modification of the soil temperature and water content regimes by a crop residue mulch: experiment and modelling

Unchopped crop residues are widely used in the tropics for reducing erosion or soil temperature and for soil water conservation. Quantitative estimation of the mulch influence on the mass and energy exchanges between the soil and the atmosphere is necessary for assessing the positive or negative mulch effects. A mechanistic model of heat and water transfer at hourly time intervals in a soil-mulch system was developed. Soil temperature and water content changes were simulated with a coupled heat and mass transfer model. Radiative and convective exchanges in the mulch were simulated as in plant canopies. The model also deals with rain interception processes. An experiment was performed to estimate how the mulch changes the soil conditions and to validate this model. Soil temperature, water content, and energy fluxes were measured over a mulched and unmulched plot. Experimental results showed that the mulch reduced soil evaporation, and soil temperature (average and amplitude). The model was calibrated by fitting only one mulch parameter. This allowed a correct simulation of the thermal exchanges in the soil. More accurate simulation of diffusive transfers through the mulch would need further investigations. Simulations are made to study the influence of the mulch leaf area index (LAI) on soil water content and temperature. An LAI of 4.0 limits more evaporation but intercepts more rainfall than an LAI of 1.0 which is consequently more efficient for soil water conservation. On the other hand, the mulch with the highest LAI has better insulating properties and is more useful to prevent soil heating.

Influence of Endosulfan Sprays and Aluminum Mulch on Sweetpotato Whitefly Disorders of Zucchini Squash and Tomatoes

Sweetpotato whitefly (Bemisia tabaci Gennadius) (SPWF) is a major pest throughout the southern USA. It is associated with the economically important disorders tomato irregular ripening (TIR) and squash silver leaf (SSL). Two possible components of SPWF management are the insecticide endosulfan (6,7,8,10,10-hexachloro-1,5,5a,6,9,9a-hexahyde-6,9-methano-2,4,3-benzodioxathiepin 3-oxide) and aluminum reflective mulch. This study was conducted to determine the effect of these control procedures, separately or in combination, on SPWF populations, the TIR and SSL disorders, fruit quality, and fruit yield of tomatoes (Lycopersicon esculentum Mill.) and zucchini squash (Cucurbita pepo L.). These parameters were evaluated in field plots during both the spring and fall of 1990. Tomato fruit yield increased (13 000 to 39 000 lb/acre), culls decreased (45 to 7%), and the percentage of TIR fruit decreased (52 to 22%) in the spring experiment as a result of endosulfan spray applications. Endosulfan sprays had no detectable effect on tomato fruit quality or yield in the fall experiment, and aluminum reflective mulch had no effect during either season. Zucchini squash yields were not affected by aluminum reflective mulch or weekly endosulfan spray applications in either experiment. Endosulfan reduced the percentage of plants with symptoms of squash SSL from 54 to 22% in the spring experiment. No SSL occurred in the fall planting. The increase in SPWF population in the squash and tomato plots was not affected by the aluminum reflective mulch or endosulfan sprays during either season. Our data suggest that environmental or physiological factors in combination with SPWF influence the incidence of SSL on squash and TIR on tomatoes. Research Question Sweetpotato whitefly (Bemisia tabaci Gennadius) can cause damage on squash (Cucurbita pepo L.) and tomatoes (Lycopersicon esculentum Mill.) by both direct feeding and the viruses it transmits. This study compares the influence of endosulfan (6,7,8,10,10-hexachloro-1,5,5a,6,9,9a-hexahyde-6,9-methano-2,4,3-benzodioxathiepin 3-oxide) sprays and reflective aluminum mulch on whitefly populations and the whitefly-induced disorders squash silver leaf and tomato irregular ripening. Literature Summary Several insecticides, including endosulfan, are known to reduce sweetpotato whitefly populations. Various colored mulches, including aluminum, also have been shown to reduce whitefly populations. Study Description Tomatoes and zucchini squash were grown in the field in the spring and fall of 1990 in Ft. Pierce, FL. Each of the plantings was divided into plots, which were treated with a weekly spray application of endosulfan, aluminum reflective mulch, both endosulfan and aluminum mulch, or neither endosulfan nor aluminum mulch. Sweetpotato whitefly populations, the incidence of tomato irregular ripening and squash silver leaf, and tomato and squash yields were monitored throughout the growing season. Applied Question Do endosulfan sprays and/or aluminum reflective mulch influence tomato or squash yields, tomato irregular ripening or squash silver leaf, or sweetpotato whitefly populations? Tomato yields were significantly increased in plots with weekly applications of endosulfan in the spring experiment, but not the fall experiment. The percentage of tomato irregular ripening also was reduced significantly by the endosulfan spray treatments in the spring experiment. Marketable squash yields were not affected by any of the treatments. In the spring experiment, however, weekly endosulfan spray applications reduced squash silver leaf symptoms. There were no significant differences in the mean weekly adult sweetpotato whitefly populations for any of the treatments in either the spring or fall experiments. In addition, aluminum painted mulch had no effect on tomato or squash yields, fruit quality, sweetpotato whitefly induced diseases, or adult sweetpotato whitefly populations. Table 1. Influence of endosulfan sprays and aluminum reflective mulch on tomato and squash yields, tomato irregular ripening and squash silver leaf, and sweetpotato whitefly populations. Tomatoes* Squash* Spring Fall Spring Fall Treatment Yield† TIR SPWF Yield† TIR SPWF Yield† SSL SPWF Yield† SSL SPWF Endosulfan + + - - - - - - - - NA - Reflective mulch - - - - - - - - - - NA - Endosulfan plus + + - - - - - + - - NA - reflective mulch * A plus sign indicates that the yield or incidence was significantly greater (P = 0.05%) than that of the untreated control. A minus sign indicates the yield or incidence was not significantly greater. NA indicates no squash silver leaf was present in the plots. † Yield was measured in both number and weight of marketable fruit per acre.

HOREHOUND (Marrubium vulgaris L.) PRODUCTION IN NORTHERN AMERICA: RESPONSES TO MULCH, SHADING, AND NITROGEN TREATMENT

Mulch, light level, and nitrogen fertilization were tested for their effects on productivity of horehound (Marrubium vulgaris L.). Yield of this plant increased under mulched conditions and with the addition of nitrogen fertilizer. Yield decreased with reduced light levels. Productivity of individual plants correlated with the number of branches per plant, leaf size, and leaf chlorophyll content. The number of branches per plant decreased with increased shading, but increased with increased nitrogen fertilization. The influence of mulch and shading on productivity could be due to the changes in soil temperature and in soil water potentials. Full-sun, high nitrogen, and mulch are suggested for optimum field production of horehound.

Potato (Solanum spp.) in the hot tropics III. Influence of mulch on weed growth, crop development, and yield in contrasting environments

Abstract Eighteen experiments at three hot tropical sites (5–12 °S, 180–800 m) within Peru were run with various mulches over a 4-year period. Mulch, although suppressing weed growth, favoured both crop emergence and the stand of tuber-bearing plants at final harvest. Canopy development, crop cover and light interception over the season were almost invariably improved by mulch. Tuber initiation, when measured, was earlier and tuber growth rates greater for mulched plants. Tuber yield was consistently increased by mulch in all but two experiments, averaging 25% over all experiments. Yield improvements due to mulch were less evident at the hottest site, where high soil temperature (> 25 °C) during the night at tuber depth, high natural reflectivity of the soil (0.18), a large sand fraction in the soil, and cloudy days and nights, were considered responsible for inconsistent benefits of mulch on tuber yield. At another site, where mulch was also tested during the rainy season, yield was on average improved by mulch in a proportion similar to that during the dry season at the same site. Mulch was particularly beneficial in improving all measured aspects of crop growth and yield when combined with agronomic treatments that, on their own, predisposed plants to greater heat stress. For example, mulch was more effective in ridge than on the flat plantings, at planting depth less than 7 cm, at lower plant populations and for small-canopied determinate clones. Environmental and biological criteria for the successful use of mulch for potato cultivation in hot climates are discussed.

Influence of Mulch, Tillage, and Diphenamid on Weed Control, Yield, and Quality in No-Till Flue-Cured Tobacco (Nicotiana tabacum)

Field experiments were conducted to determine the effects of various densities of four fall-seeded small grain mulches and diphenamid (N,N-dimethyl-α-phenyl benzeneacetamide) on weed control, yield, and quality in no-till flue-cured tobacco (Nicotiana tabacumL. ‘McNair 944’). A greenhouse study investigated the effects of non-soil-incorporated mulch from the same small grains plus alfalfa (Medicago sativaL.) on various growth parameters of tobacco (‘Speight G-70’). None of the mulches used in the greenhouse study adversely affected growth of the tobacco. Mulch from rye (Secale cerealeL. ‘Abruzzi’) killed about 2 weeks before transplanting plus diphenamid provided better annual broadleaf weed control (85%) than wheat (Triticum aestivumL. ‘McNair’), barley (Hordeum vulgareL. ‘Keowee’), and no mulch. Oat (Avena sativaL. ‘Brooks’) mulch resulted in 80% broadleaf weed control. There were no differences in annual grass control (which was short lived) among mulches but control was lower in the no-mulch treatment. Rye mulch resulted in a 22% increase in the control of broadleaf weeds compared to no-mulch. Yield of the no-till tobacco did not differ among mulches and averaged 82% of that conventionally grown. The quality was not affected. The rye mulch did not affect the yield or quality of tobacco when compared to a nonmulch, noncultivated treatment. The 18% decrease in the no-till yield was apparently the result of the lack of tillage and increased weed interference and was not due to adverse effects from the rye.

Influence of Mulch on Residue Accumulation and on Injury to ‘Richhaven’ Peach trees from 2,6-Dichlorobenzonitrile (Dichlobenil)1

Abstract Hay mulch applied only the year of planting under ‘Richhaven’ peach trees reduced foliar injury following annual applications of dichlobenil. Dichlobenil residues were greater than those of its breakdown product, 2,6-dichlorobenzamide (BAM), in mulch and at 0-15 cm soil depth under mulch. Mulch did not reduce amount of dichlobenil in soil. Only dichlobenil at 13.44 kg/ha, twice the rate labeled for usage under fruit trees, applied on mulch residue partially prevented an influx of annual weeds.