Cover Crop Cultivation Research Articles

Effects of hairy vetch, rye, and alternating cultivation of rye-vetch cover crops on soil nutrient concentrations and the production of red pepper (Capsicum annuum L.)

SummaryMost organic farmers in South Korea use a synthetic plastic film mulch to control weeds, plus high amounts of organic nutrients sourced from outside the cropping area, due to a lack of information on crop rotations using legume or deep-rooting cover crops. We have evaluated the effects of cover crop rotation on soil and plant nutrition during red pepper (Capsicum annuum L.) production from 2002 to 2005. The four treatments applied were: (i) a conventional farming (CF) system without cover crop rotation, or (ii) three organic farming (OF) systems, which either rotated the annual production of red peppers with hairy vetch (OF+HV), or rye (OF+R) from 2002 to 2004, or had an alternating cultivation of rye in 2002 and in 2004 with hairy vetch in 2003 (OF+R-HV). The OF+R system increased the below-ground biomass [39 MT ha–1, fresh weight (FW)] of the rye cover crop, but the above-ground biomass of the cover crop (22 MT ha–1 FW) was similar to those in the OF+HV and OF+R-HV systems. All OF systems, especially OF+HV, increased the soil pH, as well as P, K, Ca, and Mg concentrations to a soil depth of 0 – 20 cm in 2003, and pH, total-N, and K concentrations in 2005. Soil pH, electrical conductivity, and macro-nutrient concentrations decreased from 20 – 100 cm soil depth. All three OF systems reduced the bulk density of the soil and increased soil porosity compared to the CF system. Higher mineral nutrient concentrations in plants grown in the CF system compared to the three OF systems occurred only for Mg in 2003. The CF system increased marketable fruit yields, but did not increase the annual gross income. The highest crop value was observed in the OF+HV system. There was a net loss of N (–9 kg ha–1) in the OF+HV system in all 3 years, while the OF+R system had the highest positive balance level of N (54 kg ha–1).Therefore, the leguminous cover crop (hairy vetch) was useful as a green manure to increase annual gross incomes, increase N-use efficiency, and reduce soil N losses.

Plantas de cobertura e adubação nitrogenada na produção de milho em sistema de plantio direto

A utilização de plantas de cobertura do solo pode otimizar o aporte de material orgânico e nutrientes e proteger o solo dos processos erosivos enquanto o N é um dos nutrientes mais exigidos pelas culturas agrícolas, podendo tornar-se um fator limitante de seu rendimento. Neste contexto, realizou-se um experimento para avaliar a influência de três diferentes leguminosas usadas como plantas de cobertura sobre os componentes morfológicos e de produção do milho cultivado em sucessão sob sistema de plantio direto, na ausência e na presença de adubação nitrogenada mineral (80 kg ha-1 de N) na forma de sulfato de amônio. O estudo foi desenvolvido em Latossolo Amarelo nos tabuleiros costeiros do estado de Alagoas. Os componentes de produção do milho apresentaram melhores resultados em sucessão à crotalária spectabilis. Constatou-se efeito da interação entre adubação verde e adubação nitrogenada resultando em maior produtividade de grãos para a cultura do milho.

Matéria seca de plantas de cobertura, produção de cebola e atributos químicos do solo em sistema plantio direto agroecológico

O cultivo e a deposição de resíduos de plantas de cobertura em sistema plantio direto podem afetar os atributos químicos do solo e a produção de cebola. O trabalho objetivou avaliar a interferência do cultivo de plantas de cobertura sobre a produção de cebola e sobre os atributos químicos do solo em sistema plantio direto (SPD) agroecológico. O experimento foi conduzido na EPAGRI, em Ituporanga (SC), em um Cambissolo Húmico, nas safras de 2010 e 2011. Em abril, foram implantados os tratamentos: testemunha com vegetação espontânea (T1); cevada (2010)/aveia-preta (2011) (T2); centeio (T3); nabo-forrageiro (T4); centeio + nabo-forrageiro (T5); e cevada (2010)/aveia-preta (2011) + nabo-forrageiro (T6). Aos 60, 80 e 95 dias após a semeadura (DAS) das espécies de inverno, coletou-se a parte aérea das plantas e determinou-se a produção de matéria seca por hectare. Em julho, foram transplantadas mudas de cebola e, em novembro, avaliou-se a produção. Após o acamamento das plantas de cobertura de inverno e a colheita da cebola, foi coletado solo na camada de 0-10 cm e submetido à análise de atributos químicos. O cultivo e a deposição dos resíduos de matéria seca das espécies de plantas de cobertura em SPD contribuíram para o aumento e a manutenção da produção total de cebola ao longo dos anos. Os atributos químicos do solo, com exceção do K trocável, P disponível e valores de saturação da CTCpH7,0 por bases não foram afetados pelo cultivo de plantas de cobertura.

Weed Control in a Newly Established Organic Vineyard

Consumer demand for organic and sustainably produced products has increased the interest in organic wine grape (Vitis vinifera) production. However, organic production can be challenging, and weed management is a critical issue during the establishment of an organic vineyard. In 2009, the effectiveness of five cover crop treatments and cultivation regimes was evaluated for two years for weed control in a newly established organic vineyard of ‘Pinot noir précoce’ and ‘Madeleine angevine’ grape cultivars in northwestern Washington State. Alleyway management treatments were cultivation in alleyways with hand weeding in the vine row (control), grass cover crop which included perennial ryegrass (Lolium perenne ssp. perenne) and red fescue (Festuca rubra ssp. arenaria) seeded in the alleyway and in-row tillage with a specialty offset-type cultivator, winter wheat (Triticum aestivum) cover crop with in-row string-trimming, austrian winter pea (Pisum sativum ssp. sativum var. arvense) cover crop with in-row string-trimming, and winter wheat–austrian winter pea cover crop mix with in-row string-trimming. In 2009, weed dry biomass was lowest in the alleyway of the control (0.8 g·m−2) and offset cultivator treatments (6.3 g·m−2) on 3 Aug. and tended to be lowest in the alleyway of the control (4.8 g·m−2) and offset cultivator treatments (16.0 g·m−2) on 27 Sept. In the second year of establishment (2010), winter wheat and austrian winter pea were eliminated from the plots by mid-July, and white clover (Trifolium repens) and perennial ryegrass were the dominant weed species and accounted for a majority of the total weeds. On average over the two-year period, the control treatment required the most time for alleyway management (92 h·ha−1) followed by the offset cultivator treatment (64 h·ha−1), while the winter wheat, austrian winter pea, and winter wheat–austrian winter pea mixture required 32 to 42 h·ha−1. ‘Madeline angevine’ produced more shoot growth than ‘Pinot noir précoce’ in Sept. 2010 (42.3 and 25.9 cm respectively), and shoot growth of both cultivars in the control treatment was significantly longer (125.0 cm) than under any other treatment (55.4 to 93.0 cm), illustrating the importance of weed control during vineyard establishment. In this study, the most effective weed management regime, although also the most time consuming, included a vegetative-free zone around the vines (e.g., in-row) maintained by hand weeding and a cultivated alleyway.

Contribution of winter cover crop amendments on global warming potential in rice paddy soil during cultivation

Background and aims Winter cover crop cultivation during the fallow season has been strongly recommended in mono-rice paddy soil to improve soil quality, but its impact in increasing the greenhouse gases (GHGs) emissions during rice cultivation when applied as green manure has not been extensively studied. In order to recommend a preferable cover crop which can increase soil productivity and suppress GHG emission impact in paddy soil, the effect of winter cover crop addition on rice yield and total global warming potential (GWP) was studied during rice cultivation.

Considering winter cover crop selection as green manure to control methane emission during rice cultivation in paddy soil

Cover crop cultivation during the cold fallow season has been strongly recommended in mono-rice cultivation system to improve soil quality. Its addition as green manure could stimulate methane (CH4) emission in the submerged paddy soil during rice cultivation, but its effect has not been evaluated well. Leguminous Chinese milk vetch (hereafter milk vetch) and non-leguminous rye were seeded after rice harvesting in 2008 and 2009, and total above-ground biomasses were incorporated with the recommended mineral fertilizers (NPK+milk vetch, and NPK+rye, respectively) before rice transplanting in 2009 and 2010. No fertilization (control) and mineral fertilization alone (NPK) plots were installed for comparison. Methane flux which was investigated by the closed chamber method during rice cultivation was significantly increased by chemical fertilization to ca. 80–250% over the control (138–141kgCH4ha−1), but increased more markedly by cover crop biomass addition to ca. 28–121% over the NPK treatment. Milk vetch was more effective on stimulating less CH4 emission (28–61% increase over NPK) and improving rice productivity (18–31% increase over NPK) than rye (86–121% increase of CH4 emission and −3–6% of yield increase over NPK). As a result, the total CH4 flux per grain yield was significantly increased by rye addition, but were similar between the NPK+milk vetch and NPK treatments. Conclusively, low C/N ratio cover crop like milk vetch might be more recommendable green manure to minimize CH4 emission impact and increase rice productivity than high C/N ratio cover crop like rye in paddy soil.

Arbuscular mycorrhizal colonization increases phosphorus uptake and growth of corn in a white clover living mulch system

White clover (Trifolium repens L.) living mulch, a cover crop cultivation system, has been shown to improve phosphorus (P) nutrition and increase the yield and arbuscular mycorrhizal colonization rate of the main crop without inoculation of fungi. However, it remains unclear whether the P uptake of corn (Zea mays L.) in living mulch is promoted directly by arbuscular mycorrhizal colonization. We performed a pot experiment to test the hypothesis that living mulch increases the P uptake of corn by promoting arbuscular mycorrhizal colonization. The experimental design was a 2 × 2 factorial arrangement using fungicide treatment (fungicide application or no fungicide application) and cropping system (living mulch or no mulch). The fungicide dazomet was used to inhibit arbuscular mycorrhizal colonization. Without fungicide application, the P concentration and dry weight of the corn shoots were greater in the living mulch than in the no mulch treatment, indicating that living mulch improved the P nutrition and growth of corn. Fungicide application in living mulch, however, decreased the P concentration, dry weight of corn shoots, and arbuscular mycorrhizal colonization compared with no fungicide application. These results suggest that living mulch increases the P uptake of the main crop by promoting arbuscular mycorrhizal colonization by indigenous fungi.

Fifteen years of no till increase soil organic matter, microbial biomass and arthropod diversity in cover crop-based arable cropping systems

The physical, chemical and biological properties of soil may be modified by tillage, fertilization and cover crops. However there is little knowledge on long-term effects on soil properties, notably under Mediterranean climate. Moreover, biological indicators such as micro-arthropods can be used for a cost-effective analysis of soil biodiversity. Here, we studied physical and biological properties of a sandy loam soil in central Italy under a 4-year rotation of maize–durum wheat–cover crop–sunflower–durum wheat–cover crop during 15 years. We analysed the effects of two tillage systems, conventional tillage (CT) and no-tillage (NT); two N fertilization rates, without N and medium N level; and three soil covers: cash crop residue as control, Brassica juncea and Vicia villosa. Results show that no tillage increased soil organic matter content in the upper 10-cm layer (3.31%) compared to the conventional tillage (2.19%). No tillage also improved structure stability and lowered bulk density in the same soil profile. No-tillage systems showed higher soil microbial biomass (+71%) and respiration (+44%), and a higher abundance and diversity of micro-arthropods. We conclude that no tillage is an effective measure to improve the physical and biological quality of soil in Mediterranean conditions. No-tillage positive effect can be enhanced by the right choice of N fertilization and cover crop cultivation. Bio-indicators such as micro-arthropods can be very predictive of soil habitability by organisms.

Comparison of Carbon Sequestration Potential of Winter Cover Crop Cultivation in Rice Paddy Soil

BACKGROUND: Cultivation of winter cover crops is strongly recommended to increase land utilization efficiency, animal feeding material self-production, and to improve soil and environmental quality.

Sistemas de produção e sua influência na cultura do milho safrinha em plantio direto

The use of animal manure in agriculture coupled with the cultivation of cover crops can provide sustainability to agricultural systems. Aiming to evaluate the effect of cropping systems and nutrient sources in the culture of corn, we conducted an experiment on Oxisol in no-tillage system in Marechal Cândido Rondon (Parana, Brazil). The experiment was carried out in a randomized block design with four replications and treatments arranged in a 2 x 3 factorial consisting of two cropping systems (crop rotation and rotation with cover crops) and three nutrient sources (mineral, organic and organomineral). Organic and organomineral fertilization consisted of hen manure alone and combined with mineral fertilizer. This study describes the effect of different production systems on the cultivation of out-of-season corn (2008 harvest) in an experiment set up in 2006. The cultivation of out-of-season corn in rotation with cover crops enabled higher production of whole plant silage, but it did not affect grain yield. The nutrient sources did not affect the development of corn, both for silage and grain production. The adoption of cover crops and organic fertilizers can promote more sustainable production systems.

Cover crops alter phosphorus soil fractions and organic matter accumulation in a Peruvian cacao agroforestry system

In many tropical soils, excessive weath- ering of primary minerals confounded by intense agricultural production has resulted in the depletion of organic matter and plant available forms of phosphorus (P). Long-term growth of cover crops in tropical agroforestry systems have been shown to influence nutrient cycling, and soil organic matter pools. The objective of this experiment was to assess the affect of 2 years of cover-crop cultivation on organic matter accumulation and P bioavailability using Mehlich I and sequential fractionation methods. The experiment included six treatments in the understory of a cacao-plantain agroforestry system adjacent to lower montane tropical forests of the San Martin district of Eastern Peru. Cacao and plantain formed the primary canopy on otherwise abandoned agricultural land. The treatments consisted of four perennial leguminous cover crops (Arachis pintoi, Calopogonium mucunoides, Canavalia ensiformis, and Centrosema macrocarpum), a non-legume cover crop (Callisia repens), and a control treatment (no cover crop). After only 2 years of cultivation, results suggest that all cover crop species accessed residual P pools in 0-5 cm soil depths as indicated by a decrease in the 0.5 M HCl extractable P pools when compared to control. Additional use of residual P pools by A. pintoi and C. macrocarpum were indicated by significant reduction in the 6.0 M HCl extractable P pool. Relative to control, there was no treatment effect on soil organic matter content; however significant differences occurred between treatments. The C. ensiformis, C. mucunoides and C. repens treatments in 5-15 cm soil depths contained significantly more organic matter than the A. pintoi treatment. In 15-30 cm soil depths the C. ensiformis treatment contains significantly more organic matter than the A. pintoi treatment. Continued research should focus on monitoring the long-term effects of cover crop cultivation on the bioavailability of soil P pools in surface soil horizons, development of organic matter pools and the productivity of the agroforestry species.

Comparison of Soil Physical Properties in Conventional and Organic Farming Apple Orchards

Soil physical properties in organic farming apple orchard were evaluated in relation to conventional farming to better understand the effects of organic farming system on soil quality. Two adjacent apple orchards, matched by soil type, were chosen to ensure the same pedological conditions except management system. Soil samples were collected from middle of two adjacent trees along the tree line at two depths of 5-20 and 20-35 cm in September 2006. Contents of organic matter in organic farming soil were twice as much as those found in soil of conventional farming. The higher level of organic matter in organic farming soil was reflected through a consequent trend in improved soil physical properties. Organic farming produced greater aggregation in >2 mm size and increased aggregate stability. Bulk density was lower by 13% and hence porosity was higher in soils of organic farming as compared with conventional farming. Water holding capacity was significantly greater with organic farming by >17% over conventional farming. The capacity of organic farming to improve soil physical properties can be contributed to the regular application of relatively large amount of organic materials and the sustainable ground-cover managements, mulching with compost and cover crop cultivation.

Light Intensity Effects on Growth and Micronutrient Uptake by Tropical Legume Cover Crops

ABSTRACT Cover crops are important components of a sustainable crop-production system in plantation crops such as cacao (theobroma cacao), coffee (Coffee arabica), oil palm (Elaeis Spp.), and banana (Musa Spp.). Optimal growth of cover crops in plantation agriculture is determined by adaptability of crop species, light intensity reaching their leaf canopies, and their nutrient-use efficiencies, including those of micronutrients. An experiment was conducted in a climatically controlled growth chamber to evaluate the influence of levels of light intensity on growth and micronutrient [boron (B), copper (Cu), iron (Fe), manganese (Mn), and zinc (Zn)] uptake parameters in legume cover crops. Two photosynthetic photon flux density (PPFD, 200 and 400 μmol m−2 s−1) light treatments were imposed on nine legume species (joint vetch (Aeschynomene americana), sunhemp (Crotalaria juncea L.), Crotalaria rchroleuca, showy crotalaria (crotalaria spectabilis), hairy indigo (Indigofera hirsute L.), lab-lab (Lablab purpureus), sesbania (Sesbania microcarpa), Brazilian stylo (Stylosanthes guianensis), and cowpea (Vigna unguiculata)). Overall, light intensity significantly affected growth, micronutrient uptake, and use-efficiency ratios; with few exceptions, interactions between cover crop species and PPFD were also significant. Such PPFD × crop species interactions show that the cover crops used in this study differed in growth and nutrient-uptake parameters under the conditions imposed. Sunhemp, cowpea, sesbania, and lab-lab species were superior in producing shoot dry weight and in nutrient accumulation compared with other species at lower as well as at higher PPFD levels. Interspecific differences in nutrient influx and transport were observed. Influx and transport of micronutrients was in the order Mn > B > Fe > Zn > Cu. Overall, growth, nutrient uptake, and use-efficiency ratios were higher at higher PPFD than at lower PPFD. Results of this study indicate that the use of proper crop species at adequate light intensities is an important component of successful cultivation of cover crops in plantation agriculture.

Crescimento aéreo e radicular da soja e de plantas de cobertura em camadas compactadas de solo

O cultivo de plantas de cobertura com sistema radicular vigoroso em rotação de culturas pode melhorar a qualidade física de solos compactados. O objetivo deste trabalho foi avaliar o crescimento aéreo e radicular da soja e de cinco espécies utilizadas como plantas de cobertura de verão (guandu, guandu anão, mucuna preta, labe labe e crotalária juncea), em solo submetido a três níveis de compactação em subsuperfíce. Utilizou-se um Nitossolo Vermelho argiloso em vasos montados com anéis de PVC sobrepostos, com diâmetro interno de 20 cm e altura de 50 cm. A camada compactada localizada de 20-30 cm de profundidade foi caracterizada pelas densidades do solo de 1,13, 1,34 e 1,56 g cm-3 e 0,26, 0,66 e 1,98 MPa de impedância mecânica, respectivamente. Aos 60 dias da emergência das plantas, determinaram-se as massas da matéria seca da parte aérea e das raízes, a densidade do comprimento radicular e o diâmetro médio radicular. Apesar de alterar a distribuição do sistema radicular ao longo do perfil do solo, o impedimento físico em subsuperfície não diminuiu a produção total de raízes da soja e dos adubos verdes, com exceção da crotalária juncea. A mucuna preta foi a leguminosa mais tolerante e a soja a mais sensível à compactação do solo. O sistema radicular da crotalária juncea apresentou potencial de formação de "bioporos" compatível ao da mucuna preta, apesar de ter sido relativamente mais sensível à compactação do solo. O diâmetro médio das raízes da soja e da crotalária juncea apresentou correlação significativa com o crescimento radicular dentro da camada de solo compactado.

Potencial da utilização de coberturas vegetais de sorgo e milheto na supressão de plantas daninhas em condição de campo: I - plantas em desenvolvimento vegetativo

A supressão da infestação de plantas daninhas por espécies cultivadas como culturas de cobertura pode ocorrer durante o desenvolvimento vegetativo das espécies cultivadas como cultura de cobertura, nos estádios precoces de desenvolvimento, ou após a sua dessecação. Efeitos de competição e alelopáticos exercidos durante a coexistência das plantas de cobertura com as espécies daninhas podem ser responsáveis pelo efeito supressivo. Dois experimentos foram realizados a campo, em 1999/2000 e 2000/2001, na área experimental da Faculdade de Agronomia da UFRGS, em delineamento experimental de blocos ao acaso com quatro repetições, objetivando determinar os efeitos de plantas vegetando de genótipos de sorgo, com capacidade distinta de produção de extratos radiculares hidrofóbicos, sobre a supressão de plantas daninhas. Em 1999/2000, os tratamentos foram constituídos pelos genótipos de sorgo RS 11, BR 601 e BR 304, representantes de três classes de produção de extratos radiculares hidrofóbicos em laboratório, pelo genótipo de milheto Comum RS e por uma testemunha sem culturas. Em 2000/2001, os tratamentos foram resultantes da combinação do fator genótipo e do fator posição das plantas daninhas (linha ou entrelinha das culturas). Nos dois anos experimentais, a densidade e o crescimento de plantas daninhas (SIDRH, BIDSS e BRAPL) foram semelhantes entre os genótipos de sorgo e entre estes e o do milheto. Isso ocorreu independentemente do local avaliado, na área total ou individualmente nas linhas e entrelinhas das culturas, indicando ausência de efeito supressor de exudatos hidrofóbicos a campo. No primeiro ano, aos 30 dias após a semeadura, reduções de 41% de infestação e de 74% de massa seca total de plantas daninhas foram observadas, comparando-se os tratamentos cobertos com culturas à testemunha sem culturas, enquanto no segundo ano, aos 14 dias após a semeadura, não foram observadas diferenças entre a área onde havia plantas de sorgo ou milheto e a testemunha descoberta. A densidade de plantas daninhas nas linhas foi inversamente proporcional à população de plantas vivas de sorgo nesse local.

Use of cover crops in short rotation hardwood plantations to control erosion

This study was designed to test whether the cultivation of cover crops between tree rows in short-rotation woody crop (SRWC) plantations could reduce erosion. Sweetgum ( Liquidambar styraciflua L.) seedlings were planted as the SRWC at a 1.5×3 m spacing. Four cover crops, annual ryegrass ( Lolium multiflorum L. a winter annual grass); tall fescue ( Festuca arundinacea L. a cool-season perennial grass); crimson clover ( Trifolium incarnatum L. a winter annual legume); and Interstate sericea lespedeza [ Lespedeza cuneata (Dumont) G. Don. a summer growing-perennial legume], were tested at two different strip widths (1.22 and 2.44 m) in comparison with complete competition control. Erosion was measured from 1 August, 1995 to 8 March, 1997 (585 days) by sediment accumulation near the fence where 72 PVC pipes were inserted into soil on a 4.65 m 2 (50 ft 3) grid area of each plot. The total rainfall recorded during this period was 2422.91 mm (95.3 in.). All cover crops reduced erosion over the complete competition free plot (control), although tall fescue performed poorly at the narrow strip width. There were no significant differences between grasses and legumes for erosion control. Winter annual crops provided significantly more erosion protection than summer growing-perennials. With the exception of tall fescue, narrow strip widths performed as well as wider strip widths. The results indicate that cover crops ryegrass, crimson clover, lespedeza and tall fescue controlled about 64, 61, 51 and 37% soil erosion respectively as compared to the control during the critical early years of stand development in SRWC hardwood plantations.

Comparison of Ground Surface Spiders in Four Central Florida Ecosystems

Ground surface spider populations were studied using can traps for 3-1/2 years on sand-pine dunes, pine flat-woods, citrus groves, and residential areas in central Florida. Twenty-three prevalent (0.5 or more percent of total population) species involving, primarily, 6 prevalent (5.0 or more percent of total population) families occurred in distinctive, specifically different, ground surface spider populations in each ecosystem. The sand-pine dune population was 53% lycosid, 19% gnaphosid, and 18% salticid; the pine flat-woods, 64% lycosid, 21% salticid, and 5% linyphiid; the residential area, 54% lycosid, 23% theridiid, and 16% linyphiid; and the citrus grove, 38% clubionid, 19% theridiid, 18% lycosid, and 11% linyphiid. The population in the citrus grove was also only 1/3 as large as those of the other ecosystems. Most of the differences among the populations of the sand-pine dunes, pine flat-woods, and residential areas seemed to be the result of ecologically-equivalent species replacement, but the strikingly different citrus grove population could be the result of repeated soil surface disturbance during cover crop cultivation.

Substantiation of the causes of soil degradation and desertification in Ukraine

Purpose. To substantiate the main causes of land degradation and desertification in Ukraine in conditions of intensification of agricultural production and climate change; to carry out a comparative assessment and calculations of their balance. Methods. Monitoring studies, system and statistical analysis and their synthesis. Results. The volumes of crop production in Ukraine are highlighted. Limiting factors in agricultural production have been identified: global climate change, declining nutrient content in soils and decrease in the level of their fertility. The volumes of nutrient removal by plant products are analyzed. It is established that both the content of nutrients in crop products and the removal of nutrients from the soil loses more than 2 million tons of active substance of the main elements: nitrogen, phosphorus and potassium. On the basis of economic calculations it is proved that the volumes of mineral fertilizers are identical to the volumes of the removed nutrients with exported agricultural products: per 1 ha of sown area of the exported crops 116 kg of active substance, or N74P24K18, is removed with a crop yield. It is substantiated that the current level of exploitation of soil resources will lead to their degradation and reduction of natural fertility. Based on the analysis of agricultural production, it is argued that the question of the feasibility of increasing grain production in Ukraine to the level of 90 million tons is debatable due to the diversity of forms of management and different levels of resource provision in technology. After all, nitrogen, phosphorus and potassium in the amount of about 56.5 billion UAH are annually exported from the country with agricultural products. Conclusions. With such a level of intensification of production and export of plant raw materials, compensation for the export of nutrients and prevention of soil degradation requires annual application against the background of N76P17K17 additional N74P24K18, which will amount to N150P41K35 per hectare of sown area. In addition to increasing the rates of mineral fertilizers, in order to preserve soil fertility it is necessary to apply organic fertilizers, introduce cultivation of perennial legumes and cover crops in crop rotation, use plant residues as fertilizers, lime soils etc.

The Influence of Cover Crop Cultivation on Populations of Injurious Insects and Mites in Florida Citrus Groves

Cultural practices involving the natural ground cover or cover crop vary considerably from area to area and grove to grove in Florida. This variation is, in some instances, governed by the level of the water table or the type of soil involved. More frequently, however, cultivation is modified by the opinions of the grower. Some growers maintain weed-free groves by frequent disking, harrowing or chopping. Others permit cover crop development during the summer months but practice clean cultivation in the fall, winter and spring. Still others allow weeds and wild grasses to grow unhampered from one picking season to the next. Horticultural and agronomic reasons cited for such variations in practices include moisture conservation, soil conservation, fire protection, soil protection, tree stimulation and efficient grove management. Furthermore, many growers believe that such practices cause increases or decreases in insect and mite abundance. To date only two studies have been conducted on the influence of cover crop cultivation on insect and mite infestations. The first was an investigation by Osburn and Mathis (1944) concerning the citrus rust mite, Phyllocoptruta oleivora (Ashmead). These workers concluded that there was no difference between rust mite infestations on trees in clean cultivated plots and on trees grown in plots having a cover crop. They did, however, record stimulation of the trees in the clean cultivation plots. Two years later the same workers (Osburn and Mathis, 1946) reported markedly greater infestations of Florida red scale, Chrysomphalus aonidum (L.), on trees growing in cultivated plots than on trees in uncultivated plots. They were unable, however, to demonstrate striking differences in the percentages of parasitized scales or fungi-affected scales and concluded that tree stimulation, a result of cultivation, was the important factor in the development of larger scale infestations. The present study was conducted to obtain preliminary cultivation data on the major injurious insects and mites attacking Florida citrus and to correlate, if possible, any differences recorded with changes in the rates of parasitism or predation.

Plantation and Agriculture in Malaya, with Notes on the Trade of Singapore

ONE of the outstanding features of agriculture in Malaya is unbalanced production, characterized by the extensive cultivation of crops for export markets, and the total inadequacy of the food-crops grown in the country to supply the local demand. Rubber occupies nearly two-thirds of the cultivated area and accounts for 90 per cent. of the value of the export trade in agri? cultural products. Malaya produces about 40 per cent. of her requirements of rice, the staple food of the people. Important export crops include coconuts, pineapples, oil palm, spices, areca-nuts, and tapioca. There is a large import trade in rice, coflfee, tea, ground-nuts, sugar, tobacco, livestock, meat, dairy produce, poultry, and eggs. With the exception of the oil palm and the pineapple, crop production is mixed in character. The oil palm is grown exclusively in plantations. About two-thirds of the acreage under pineapples is now devoted to their sole cultivation. Rubber, coconuts, and other crops are grown under a variety of conditions: on large estates exceeding 100 acres in extent, on small estates which are owned mainly by Chinese, and in the typical Malay kampongs or smallholdings where rubber, coconuts, areca-nuts, gambier, and various fruits are intercultivated. The cultivation of rice under sawah conditions is the most persistent form of agriculture in the Malay kampongs. Catch-crops are cultivated with rubber, the oil palm, and other crops on newly established plantations so that there may be some return before the major crop comes into bearing about the sixth year; they include tapioca, pineapples, bananas, gambier, and Coffea robusta. The cultivation of catch-crops is decreasing owing to the dangers of soil erosion and to the cultivation of cover-crops. Methods of soil conservation are commonly employed and include various forms of drainage and the cultivation of cover-crops. The more common forms include silt pits, contour terracing (or bunding), and contour drains. Silt pits or deep trenches about 15 feet in length are dug along the contours about 15 feet apart. The silt pits along a particular contour cover the gaps in the contour above, so that storm water and soil wash are checked. The ends of the silt pits on the several contours are sometimes linked by a zigzag system of bunds or ridges. Silt-pitting is now less popular than formerly, owing partly to the high costs of construction and maintenance. In contour terracing a succession of level terraces are constructed along the contours, the soil which is thrown on the downhill side being retained by a stone wall or reinforced by the cultivation of a dense cover. On some rubber estates drains are constructed along the contours in order to check storm wash. In Malaya such drainage methods are generally considered temporary expedients while cover-crops or plants which spread rapidly over the surface of the ground are established. The dense, low-growing cover-crop reduces weeding costs, checks rain wash, binds soil particles together, assists aeration and drainage by its rootlets, and improves the texture of the soil by the addition of humus. The cultivation of a cover-crop may deprive the main crop of certain essential