Groundcover Management Systems Research Articles

Groundcover Management System and Nutrient Source Impacts on Soil Quality Indicators in an Organically Managed Apple (Malus ×domestica Borkh.) Orchard in the Ozark Highlands

The highly weathered, mineral, and often eroded and acidic soils of the Ozark Highlands region of northwest Arkansas generally have low soil organic matter (SOM) concentrations as a result of rapid organic matter turnover rates in the warm, moist climate. Orchard management practices that can improve SOM may also improve other soil quality-related variables for sustained production, which is an explicit goal for the National Organic Program (NOP). Therefore, beginning in Mar. 2006 and continuing for seven seasons, annual applications of municipal green compost, shredded office paper, wood chips, and mow-blow grass mulch groundcover management systems (GMS) in combination with composted poultry litter, commercial organic fertilizer, or a non-fertilized control as a nutrient source were implemented to evaluate their ability to alter near-surface soil quality in a newly established, organically managed apple orchard in the Ozark Highlands region of northwest Arkansas. The SOM concentration in the top 10 cm averaged 1.5% across all treatments at orchard establishment in 2006, but by 2012, SOM concentration had increased in all GMS and more than doubled to 5.6% under green compost. Similarly, soil bulk density in the top 6 cm, which averaged 1.34 g·cm−3 among treatment combinations in 2006, decreased in all GMS by 2012. Either green compost or shredded paper had the largest concentration of total water-stable aggregates across all aggregate size classes in the top 7.5 cm, whereas no differences among GMS were observed in the 7.5- to 15-cm soil depth. Green compost applied alone or in combination with commercial fertilizer had the largest estimated plant-available water (17.9% v/v) among all treatment combinations. Many soil quality-related variables measured in the various organic GMS had numerically greater values compared with an adjacent conventionally managed orchard on the same soils. Implementation of these GMS appears to provide apple producers in the Ozark Highlands and similar regions a tangible means of meeting NOP requirements for improving soil quality concurrent with production of certified organic crops. The findings also have implications for conventionally managed orchards, which have maintaining or improving soil quality as a management goal.

Groundcover Management and Nutrient Source Effects on Soil Carbon and Nitrogen Sequestration in an Organically Managed Apple Orchard in the Ozark Highlands

Orchards established on weathered, acidic mineral soils in the Ozark Highlands must be managed to meet tree nutritional requirements. However, a common characteristic of Ozark Highland soils is a relatively low soil organic matter (SOM) concentration, a condition that can have detrimental effects on orchard productivity. Organic orchard management poses specific challenges to managing competitive under-tree vegetation and supplying appropriate supplemental nutrition to maintain tree growth and cropping. In Mar. 2006, an experimental apple orchard was established to evaluate the effects of under tree, in-row groundcover management system (i.e., shredded paper, wood chips, municipal green compost, and mow-blow), and nutrient source (i.e., non-fertilized control, composted poultry litter, and pelletized organic commercial fertilizer) on SOM, carbon (C), and nitrogen (N) concentration, and soil C and N sequestration over time in an organically managed orchard in the Ozark Highlands region of northwest Arkansas. Soil organic matter, total C, and total N concentrations (soil weight basis) and contents (area basis) in the top 7.5 cm increased in all groundcover management systems from 2006 to 2011. The greatest differences were observed with municipal green compost treatments. Significant interactions between groundcover management treatment and nutrient source were only observed for SOM concentration, whereas nutrient source did not affect total C and total N concentrations or contents. Soil C sequestration rates were 0.9, 1.0, and 2.8 Mg·ha−1 per year under the shredded paper, wood chip, and green compost treatments, respectively, whereas total C content did not change over time under the mow-blow treatment. The green compost treatment was the only treatment that had significant total N sequestration occur (0.25 Mg nitrogen/ha/year). Results of this study indicate that organic cultural methods can significantly augment near-surface soil C and N contents, which will likely increase productivity, of apple orchards in the Ozark Highlands over a relatively short period time after establishment. This study has implications for orchards in similar soils or environmental circumstance and for both organic and conventional management systems.

Mulch type and application of manure and composts in strawberry (Fragaria × ananassa Duch.) production: impact on soil fertility and yield

The objective of this research was to quantify the effect of the application of organic fertilizers: farmyard manure, vermicompost, spent mushroom compost, under two different ground cover management systems (black polyethylene and wheat straw mulch) on soil nutrient levels and strawberry yield during a two-year production cycle. The application of organic fertilizers, in the amounts equivalent to 170 kg ha -1 N, had the greatest impact on the concentration of available phosphorus, which was significantly higher on fertilized plots than on the control even two years after the application. The plots fertilized with farmyard manure and mushroom compost had higher concentrations of available potassium than the control, while the application of vermicompost did not affect the concentration of available potassium in the soil. The application of composts did not affect the concentration of available microelements in the soil, while the concentrations of Fe, Zn and Cu in the year of the organic fertilizers application were significantly higher on farmyard manure fertilized plots than on the control. The application of all three organic fertilizers had a significant effect on the mineral N concentration in the soil only in the year of the application and the following spring. However, the plots covered with polyethylene mulch had a higher mineral N concentration than the control at all sampling times. The concentration of available microelements was significantly higher in soil covered with black polyethylene mulch than in soil covered with straw mulch. Preplant application of organic fertilizers led to increase of yield, ranging from 14.3% in vermicompost treatmet to 17.3% in the farmyard manure treatment in relation to the control, only in the 1 st fruiting year. However, the application of polyethylene mulch facilitated a higher strawberry yield than straw mulch in both fruiting years.

Root distribution and demography in an avocado (Persea americana) orchard under groundcover management systems.

The effect of groundcover management systems on root demography and distribution of newly planted avocado (Persea americana Mill) trees was examined using minirhizotron techniques. We evaluated three groundcover systems: (1) bare soil (BS), pre- and post-emergence herbicides; (2) vegetation strip (VS), post-emergence herbicide applied in a 1-m wide strip centred on the tree row plus a groundcover mixture seeded between tree rows; and (3) complete groundcover (GC), covering the entire surface of the plots. Root production was higher in the non-bearing year (2009-10) than in the bearing year (2010-11). Trees in the BS plots had more roots of bigger diameter in the top 30cm of soil and trees in VS and GC plots had more roots in the 30-60cm depth and of smaller diameter. Lifespan of spring-born roots were 61 and 59% greater than those born during autumn and summer, respectively and soil depth and root diameter were positively correlated with root longevity. Lifespan of thinner roots (<0.2mm) in the BS and VS plots were 49 and 33% greater than GC respectively. Avocado trees grown in contrasting condition compared with their native habitat show high morphological root plasticity, in response to resource and non-resource competition when grown in mixed stands.

Soil erosion, runoff and nutrient losses in an avocado (Persea americana Mill) hillside orchard under different groundcover management systems

Assess the influence of different groundcover management systems on erosion and runoff processes associated with extremely steep hillside avocado (Persea americana Mill) orchards, in a Mediterranean climate with high rainfall variability. We compared several groundcover management systems at a steep hillside avocado planting in a three-year study: 1) Bare soil (BS), pre- and post-emergence herbicides; 2) Vegetation strip (VS), post-emergence herbicide applied in a 1-m wide strip on the tree row plus groundcover seeded between tree rows; 3) Groundcover (GC), over the entire plot surface. Trees in the BS plots were 44 and 53 % bigger, and had 150 and 250 % higher yields than trees in VS and GC, respectively. Runoff volumes, soil losses, dissolved organic carbon, PO4-P and total N losses were significantly higher in BS than VS and CG treatments. Total soil nitrogen (N) and carbon (C) content, C-to-N ratios, and essential plant nutrient availability were greater in the GC soil than in other treatments. Soil macroporosity and aggregate stability were 8–27 % and 25 % lower, and soil bulk density significantly higher in the BS than the VS and GC systems at the end of the study. Terbuthylazine herbicide concentrations in runoff water from BS plots ranged from 55.4 to 79.9 μg L−1, exceeding maximum allowed levels for drinking water (0.1 μg L−1). Soil erosion and runoff rates from newly planted hillside orchards are not environmentally sustainable under current growing practices where groundcover vegetation is completely suppressed. High sediment losses and herbicide residues in runoff water present serious risk of water source pollution, but these impacts can be reduced by alternative soil management systems.

Soil microbial biomass under different management and tillage systems of permanent intercropped cover species in an orange orchard

To mitigate soil erosion and enhance soil fertility in orange plantations, the permanent protection of the inter-rows by cover species has been suggested. The objective of this study was to evaluate alterations in the microbial biomass, due to different soil tillage systems and intercropped cover species between rows of orange trees. The soil of the experimental area previously used as pasture (Brachiaria humidicola) was an Ultisol (Typic Paleudult) originating from Caiuá sandstone in the northwestern part of the State of Paraná, Brazil. Two soil tillage systems were evaluated: conventional tillage (CT) in the entire area and strip tillage (ST) (strip width 2 m), in combination with different ground cover management systems. The citrus cultivar 'Pera' orange (Citrus sinensis) grafted onto 'Rangpur' lime rootstock was used. Soil samples were collected after five years of treatment from a depth of 0-15 cm, under the tree canopy and in the inter-row, in the following treatments: (1) CT and an annual cover crop with the leguminous species Calopogonium mucunoides; (2) CT and a perennial cover crop with the leguminous peanut Arachis pintoi; (3) CT and an evergreen cover crop with Bahiagrass Paspalum notatum; (4) CT and a cover crop with spontaneous Brachiaria humidicola grass vegetation; and (5) ST and maintenance of the remaining grass (pasture) of Brachiaria humidicola. Soil tillage and the different cover species influenced the microbial biomass, both under the tree canopy and in the inter-row. The cultivation of brachiaria increased C and N in the microbial biomass, while bahiagrass increased P in the microbial biomass. The soil microbial biomass was enriched in N and P by the presence of ground cover species and according to the soil P content. The grass species increased C, N and P in the soil microbial biomass from the inter-row more than leguminous species.

Long-term Effects of Four Groundcover Management Systems in an Apple Orchard

Groundcover management systems (GMSs) are essential for fruit production, but very few long-term studies have evaluated orchard GMS sustainability. We evaluated four GMSs—pre-emergence soil-active herbicides (PreHerb), post-emergence herbicide (PostHerb), a turfgrass cover crop (Sod), and hardwood bark mulch (Mulch)—in an apple (Malus domestica Borkh.) orchard over 16 years of continuous observation. There were no consistent long-term trends in fruit yields among GMSs, although during the first 5 years, yields were lower in trees on Sod. Tree growth was greater in PostHerb and Mulch than in Sod during the first 5 years, and during the next decade, trees in Mulch plots were consistently larger than in other GMSs. Total soil nitrogen (N) and carbon (C) content, C-to-N ratios, and essential plant nutrients were much greater in the Mulch soil after 16 years of treatments. Long-term responses of trees to groundcover vegetation indicated that apple trees respond adaptively to compensate for weed and grass competition. Year-round elimination of surface vegetation with residual soil active herbicides may be unnecessary or even detrimental for orchard productivity and soil fertility in established orchards. Post-emergence herbicides that reduce weed competition primarily during the summer months may offer an optimal combination of weed suppression and soil conservation.

Nitrogen Dynamics and Nutrient Budgets in Four Orchard Groundcover Management Systems

Excessive nitrogen (N) applications can increase surface and water contamination, and leaching losses may occur when N fertilizer rates are too high relative to crop demands and soil N availability. Quantifying nutrient inputs, cycling, and outputs from orchards provides a method to measure surplus of nutrients, particularly N, that may leach or runoff. We conducted a long-term study to develop N budgets based on observed nutrient dynamics under four groundcover management systems (GMSs) with and without N fertilization. Four GMS treatments were randomly assigned to 12 plots and maintained since 1992 in 2-m-wide strips within tree rows: pre-emergence residual herbicide (PreHerb), post-emergence herbicide (PostHerb), mowed-sod (Sod), and hardwood bark mulch (Mulch). We measured system N inputs in fertilizer, mulch biomass, rain, and irrigation water; N outputs in harvested fruit, surface runoff, and subsurface leaching; and internal N cycling from surface vegetation, soil mineralization, leaf fall, and pruned wood. For the year with N fertilizer (2005), the overall N balance was positive (inputs exceeded outputs) in all GMSs but greater in the PostHerb and Mulch treatments. In the year without N fertilizer (2007), the overall N balance was negative for PreHerb and PostHerb and positive for Mulch and Sod treatments. Soil mineralization and recycling groundcover biomass accounted for greater than 60% of internal N fluxes, and harvested fruit represented greater than 70% of N outputs from the system during both years. During the year with N fertilizer, N losses were 1% to 4% and 18% to 22% through surface runoff and subsurface leaching, respectively. During the year without fertilizer, surface runoff N losses were twice the subsurface leaching N losses in all GMSs.

Estimated nitrogen use efficiency, surplus, and partitioning in young apple trees grown in varied organic production systems

A certified organic apple ( Malus × domestica Borkh.) orchard was established to study the interaction of ground cover management systems (GMS) and nutrient sources (NS) on nitrogen (N) use efficiency and N surplus in the Southern U.S. for three years. Trees treated with green compost (GC) and wood chips (WC), regardless of the NS, had greater N accumulation and leaf N use efficiency compared to the shredded paper or mow-and-blow treated trees. The WC-treated trees had comparably low N surplus relative to the GC trees that induced more [NO 3 −] in soil or soil solution in the rooting zone in September in year 3. GC trees had the highest [NO 3 −] mineralization in the soil during winter. GMS had greater overall effects on the tree response variables than did the NS.

Effects of different organic apple production systems on seasonal nutrient variations of soil and leaf

An organic apple ( Malus × domestica Borkh.) orchard was established to study the interaction effects of ground cover management systems (GMS) and nutrient sources (NS) on soil and tree nutrients in the Southern U.S.A. GMS mulches as follows: green compost (GC), wood chips (WC), shredded paper (SP), and mow-and-blow (MB). Across GMS, one of three NS treatments was applied: commercial organic fertilizer (CF), poultry litter (PL), and no fertilizer (NF). GC-treated plots had greater soil solution nitrate concentrations in year 3. GC plots also maintained greater seasonal soil organic matter and macronutrient concentrations during 3 years compared with the other GMS. Seasonal foliar nutrient concentrations grown under GMS in year 3 tended to follow nutrient concentration patterns similar to those observed in conventional apple orchards. GC and WC trees had overall greater leaf area, dry weight, and total foliar nutrient contents in year 3 than the SP and MB trees.

Least limiting water range and physical quality of soil under groundcover management systems in citrus

Machinery-based farming operations used for perennial fruit crops often damage soils, particularly if the soil is wet and prone to compaction. We hypothesized that perennial vegetation growing in the interrows of orange orchards can mitigate the soil physical degradation from machinery traffic. The objective of this study was to investigate the effects of different groundcover management systems on the soil physical quality indicators including the least limiting water range (LLWR). An experiment was started in 1993 in a Typic Paleudult to evaluate three groundcover management systems: Bahia grass (Paspalum notatum) with mowing, perennial peanut (Arachis pintoi), and natural regrowth in which weeds were controlled by herbicide. The experimental design was randomized complete block with three replications. In May 2003, 216 undisturbed soil samples were collected at 0-0.15-m depths under and between wheel tracks in the orchard interrows. The soil bulk density, soil organic carbon content, resistance to penetration, soil water retention curve and soil resistance to penetration curve were determined in order to estimate the LLWR. The higher LLWR under wheel tracks in Bahia grass compared to perennial peanut or natural regrowth suggest that a better soil physical quality was achieved with Bahia grass.

Soil Physical quality under groundcover management systems in citrus

Soil Physical quality under groundcover management systems in citrus

Apple Root Growth, Turnover, and Distribution Under Different Orchard Groundcover Management Systems

Minirhizotrons were used to study root emergence, turnover, and depth distribution of apple (Malus ×domestica Borkh.) rootstocks (M.9/MM.111) under four groundcover management systems (GMSs)—pre-emergence herbicide (Pre-H), postemergence herbicide (Post-H), mowed sod grass (Grass), and hardwood bark mulch (Mulch)—that had been maintained since 1992 in an orchard near Ithaca, NY. Two root observation tubes were installed on both sides of one tree in three replicates for each GMS treatment. Roots were observed by camera at 2- to 3-weekly intervals during the growing seasons of 2002 and 2003 and from whole tree excavations in Apr. 2000. Tree growth and yield observations from 1992 to 2003 showed that Mulch and Post-H treatments produced more tree growth and higher yields than other treatments during most years; the Grass treatment usually had the smallest trees and lowest yields. More root emergence was observed in a light crop year (2002) than in a heavy crop year (2003). Pre-H treatment trees had more total roots and new roots than all other treatments, and trees in Grass plots had fewer total roots than others. Trees in Mulch plots had more shallow roots, and trees in Grass plots had more deep roots than others. Root diameter was positively correlated with overwintering root survival. The Pre-H treatment trees had greater root mortality than other trees during an unusually hot and dry growing season (2002) and this was attributed to higher shallow soil temperatures in this treatment. The GMS treatments affected root number and root depth distribution patterns. Despite microsprinkler irrigation, hot, dry weather conditions coincided with decreased root growth, increased root mortality, and reduced root median lifespan. GMS treatments affected root growth, turnover, and distribution at this orchard, and these differences were linked with long-term trends in tree growth and fruit production in this study.

Impacts of groundcover management systems on yield, leaf nutrients, weeds, and arthropods of tart cherry in Michigan, USA

Three different assemblages of cover crops were planted, fertilizer and herbicide input reduced, and mulch side-delivered in a northern Michigan tart cherry orchard to evaluate effects on tree leaf nutrients, arthropod communities, weed control, and tart cherry yield. The three treatments were compared against the conventional management system, which consisted of sod alleys and herbicide-maintained tree rows. Although fertilizer was reduced by 1/2 and herbicides eliminated in the ground cover management systems (GMSs), there was no evidence of reduced cherry yields. All GMSs provided more plant cover than the unmanipulated sod control. Biomass samples suggested that there was not enough side-delivery mulch to significantly reduce understory weed growth in the tree rows when compared to the non-mulched plots. The GMSs increased species richness, abundance, and diversity ( H′) of arthropods, despite frequent pesticide applications in all treatments. The results of the economic analysis suggest that cover cropping, half N fertilizer, and herbicide elimination may be a viable alternative to conventional groundcover management in northern Michigan.

Long-term orchard groundcover management systems affect soil microbial communities and apple replant disease severity

Apple replant disease (ARD) is a soil-disease syndrome of complex etiology that affects apple tree roots in replanted orchards, resulting in stunted tree growth and reduced yields. To investigate whether different groundcover management systems (GMSs) influence subsequent ARD severity, we grew apple seedlings in an outdoor nursery in pots containing orchard soil from field plots where four GMSs had been maintained for 14 years in an orchard near Ithaca, NY, USA. The GMS treatments were: (1) pre-emergence herbicide (Pre-H), bare soil strips maintained by applying tank-mixed glyphosate, norflurazon and diuron herbicides annually; (2) post-emergence herbicide (Post-H), sparse weed cover maintained by applying glyphosate in May and July each year; (3) mowed sod grass (Mowed Sod); and (4) bark mulch (Mulch). Soils were also sampled from the grass drive lane maintained between the trees in the orchard (Grass Lane). Sampled soils (Orchard soil) were either pasteurized or left untreated, placed into 4-L pots, and planted with one apple seedling per pot. After 3 months of growth, soil (Bioassay soil) and apple tree roots (Bioassay roots) were sampled from each pot and microbial populations colonizing samples were characterized. Seedling growth was reduced in soils sampled from all four GMS treatments compared to the Grass Lane soils. Among the GMS treatments, seedling biomass was greater in Pre-H than in the Post-H soil. Soil microbial communities and nutrient availability differed among all four GMS treatments and the Grass Lane. Root-lesion (Pratylenchus sp.) nematode populations were higher in the Mowed Sod than in the other GMS treatments. Soil bacterial and fungal community composition was assessed in Orchard and Bioassay soils and Bioassay roots with a DNA fingerprinting method (T-RFLP). Redundancy analysis indicated that soils sampled from the different GMS treatments differentially influenced seedling biomass. A clone library of 267 soil bacteria was developed from sampled Orchard soils and Bioassay roots. These communities were dominated by Acidobacteria (25% of sequences), Actinobacteria (19%), δ-Proteobacteria (12%), β-Proteobacteria (10%), and these ratios differed among the GMS soils. Members of the family Comamonadaceae were detected only in tree-row soil, not in the Grass Lanes. The dominant sequences among 145 cloned fungi associated with apple seedling roots were Fusarium oxysporum (16% of sequences), an uncultured soil fungus submitted under DQ420986 (12%), and Rhodotorula mucilaginosa (9%). In a redundancy analysis, factors including fungal and oomycete community compositions, soil respiration rates, population sizes of culturable bacteria and fungi, soil organic matter content, and nutrient availability, were not significant predictors of apple seedling biomass in these soils. Different GMS treatments used by apple growers may influence subsequent ARD severity in replanted trees, but edaphic factors commonly associated with soil fertility may not reliably predict tree-root health and successful establishment of replanted orchards.

Homogeneidade da qualidade física do solo nas entrelinhas de um pomar de laranjeira com sistemas de manejo da vegetação permanente

A qualidade física do solo é fundamental para a sustentabilidade da produção citrícola. O objetivo deste estudo foi avaliar a homogeneidade da qualidade física do solo nas entrelinhas de um pomar de laranjeira com sistemas de manejo da vegetação permanente. O estudo foi realizado em um experimento com sistemas de manejo de solo nas entrelinhas de um pomar de laranjeira 'Pêra' sobre limoeiro 'Cravo', implantado em 1993 em um Argissolo Vermelho distrófico latossólico, em Alto Paraná, região noroeste do Estado do Paraná. O delineamento experimental utilizado foi de blocos ao acaso com três repetições. Os tratamentos de sistemas de vegetação permanente das entrelinhas foram: gramínea "mato-grosso" ou "batatais" (Paspalum notatum), leguminosa amendoim forrageiro (Arachis pintoi) e o sistema de manejo tradicional com dessecação das plantas espontâneas com herbicida. Em maio de 2003, coletaram-se 216 amostras de solo indeformadas no meio da camada de 0-15 cm de profundidade e em duas posições de amostragem, no rodado e entrerrodado do trator. As amostras de solo foram usadas para determinar o teor de água em diferentes potenciais matriciais, a densidade do solo, a porosidade total e a resistência do solo à penetração. Também foram calculados a distribuição do tamanho de poros, a capacidade de aeração do solo e o índice S. A inclusão da capacidade de aeração do solo e do índice S associado à distribuição do tamanho de poros permitiu melhor entendimento das alterações físicas resultantes do manejo do solo com vegetações permanentes nas entrelinhas do pomar de laranjeira. O aumento do volume de poros drenados sob a vegetação leguminosa reduz o teor de água do solo, confirmado pela maior capacidade de aeração e pelo índice S no rodado e entrerrodado. A qualidade física do solo na entrelinha do pomar de laranjeira mantida com gramínea é mais homogênea do que daquele com vegetações espontânea ou leguminosa.

Qualidade física do solo em pomar de laranjeira no noroeste do paraná com manejo da cobertura permanente na entrelinha

O tráfego de máquinas e a compactação do solo ocorrem próximo à copa das plantas de citros, aumentando as restrições físicas do solo ao crescimento das raízes. Estratégias de manejo incluem o uso de coberturas permanentes do solo nas entrelinhas de pomares de laranjeira, mas são desconhecidos os seus efeitos na qualidade física do solo. O objetivo deste estudo foi quantificar o impacto de sistemas de manejo com cobertura permanente do solo em alguns indicadores de qualidade física do solo em um pomar de laranjeira. O estudo foi realizado em um experimento de longa duração de laranjeira 'Pêra' sobre limoeiro 'Cravo' com sistemas de cobertura permanente do solo nas entrelinhas, no município de Alto Paraná, noroeste do Paraná, em um Argissolo Vermelho distrófico latossólico, com horizonte superficial de textura arenosa. Os tratamentos de cobertura permanente nas entrelinhas com a gramínea mato-grosso ou batatais (Paspalum notatum) manejada com roçada e a leguminosa amendoim forrageiro (Arachis pintoi) foram comparados ao manejo tradicional, em que a vegetação espontânea foi dessecada com herbicida pós-emergente. O delineamento experimental utilizado foi de bloco ao acaso com três repetições. Em maio de 2003, a amostragem de solo foi realizada sob rodado e entrerrodado das máquinas nas entrelinhas do pomar. As amostras indeformadas de solo obtidas no centro da camada de 0-15 cm de profundidade foram utilizadas para determinação dos seguintes indicadores: conteúdo de água na capacidade de campo, porosidade total do solo e densidade do solo, a partir dos quais foram estimados os indicadores capacidade de aeração do solo e capacidade de armazenamento de água do solo. Amostras de solo deformadas foram coletadas nas camadas de 0-5 e 10-15 cm de profundidade, para determinação dos teores de C orgânico do solo e cálculo da taxa de estratificação de C orgânico do solo. Os indicadores de qualidade do solo, capacidade de armazenamento de água do solo, capacidade de aeração do solo e taxa de estratificação de C orgânico do solo foram eficientes na avaliação de sistemas de manejo de solo em citros. A manutenção da vegetação das entrelinhas vegetadas com a gramínea mato-grosso ou batatais melhora a qualidade física do solo, independentemente das posições rodado e entrerrodado. A qualidade física do solo é afetada negativamente na posição rodado sob o manejo com amendoim forrageiro e nas posições rodado e entrerodado no manejo tradicional da vegetação espontânea com herbicida pós-emergente.

Dissimilaridade de porta-enxertos da laranjeira 'folha murcha' sob dois sistemas de manejo de cobertura permanente do solo

Os porta-enxertos de citros são dependentes do sistema de manejo do solo nas entrelinhas. Este trabalho foi realizado com o objetivo de identificar a dissimilaridade de sete porta-enxertos para a laranjeira 'Folha Murcha' em dois sistemas de manejo da cobertura de um Argissolo Vermelho distrófico latossólico. O estudo foi realizado na Estação Experimental do IAPAR, em Paranavaí. O delineamento experimental foi de blocos ao acaso com quatro repetições, com gramínea mato-grosso ou batatais (Paspalum notatum Flügge) em três blocos e leguminosa amendoim forrageiro (Arachis pintoi Krap. &amp; Greg.) em um bloco. A produção, o desenvolvimento vegetativo e os nutrientes nas folhas da laranjeira 'Folha Murcha' foram avaliados anualmente (1997 a 2002). As análises multivariadas basearam-se nas variáveis canônicas e nos componentes principais, agrupando-os pelo método Tocher. O manejo da cobertura do solo com a leguminosa amendoim forrageiro Arachis pintoi diminui a dissimilaridade dos grupos de porta-enxertos da laranjeira 'Folha Murcha'. O manejo da cobertura do solo com a gramínea Paspalum notatum aumenta a dissimilaridade dos grupos de porta-enxertos da laranjeira 'Folha Murcha' com a inclusão dos teores dos nutrientes foliares, da produção de frutos e do desenvolvimento vegetativo das plantas. A gramínea Paspalum notatum é o melhor sistema de manejo da cobertura do solo para avaliação do comportamento de porta-enxertos da laranjeira 'Folha Murcha'.

APPLE ROOT GROWTH, TURNOVER, AND DISTRIBUTION UNDER DIFFERENT ORCHARD GROUNDCOVER MANAGEMENT SYSTEMS

Minirhizotrons were employed to study new root occurrence, turnover, and depth distribution of apple (Malus ×domestica Borkh.) rootstocks under four groundcover management systems (GMS): preemergence herbicide (Pre-H), postemergence herbicide (Post-H), mowed sod (Grass) and hardwood bark mulch (Mulch) that have been maintained since 1992 in an orchard near Ithaca, NY. Two root observation tubes were installed on both sides of one tree in three replicates for each GMS treatment. Root observations were taken at 2–3 week intervals during growing seasons of 2002 and 2003. Tree growth and yield data were collected annually since 1992. The Mulch and Post-H treatments had bigger trees and higher yields than other treatments; whereas the Grass treatment had the smallest trees and lowest yields. Higher number of new roots was observed in a light crop year (2002) than a heavy crop year (2003). Mulch trees had more shallow roots and Grass trees had fewer total roots than other treatments. Root diameter was positively correlated with overwintering root survival. The Pre-H GMS had higher root mortality during a hot and dry growing season (2002). GMS treatments affected root number and root depth distribution patterns. Hot and dry weather conditions and crop load reduced new root emergence, increased root mortality and reduced root median lifespan. GMS treatments together with environmental factors affected root growth, turnover and distribution.

Nutrição e produção da laranjeira "Folha Murcha" em porta-enxertos e plantas de cobertura permanente na entrelinha

O estado nutricional e a produção de citros não são conhecidos para as diferentes combinações copa/porta-enxertos e plantas de coberturas permanente na entrelinha. O estudo foi instalado em um experimento de laranjeira "Folha Murcha" [Citrus sinensis (L.) Osb.] com oito anos de idade, conduzido entre 1997 a 2002, no município de Paranavaí, região Noroeste do Paraná. O solo corresponde a um Argissolo Vermelho distrófico típico textura areia/franco arenoso. O delineamento experimental foi de blocos ao acaso, sendo os tratamentos constituídos por sete porta-enxertos: limoeiro "Cravo", limoeiro "Rugoso da África", limoeiro "Volcameriano", tangerineira "Cleópatra", tangerineira "Sunki", citrangeiro "C-13" e Trifoliata, com três plantas em cada parcela experimental. As repetições foram constituídas por três blocos com a cobertura Paspalum notatum e por um bloco com Arachis pintoi. Foram avaliados os teores dos nutrientes foliares e a produção de frutos da laranjeira "Folha Murcha". O manejo das entrelinhas com a leguminosa elevou os teores de N à faixa excessiva nas folhas do porta-enxerto limoeiro "Cravo", e reduziu a produção de frutos da laranjeira "Folha Murcha" em relação à gramínea. Nas entrelinhas com gramínea, a produção de frutos da laranjeira "Folha Murcha" foi dependente das safras agrícolas e dos teores foliares de Ca, Mg e Zn. A absorção máxima de Ca pelas folhas de laranjeira "Folha Murcha" precede a de Mg e Zn. Nestas condições, os porta-enxertos tangerineira "Cleópatra" e limoeiro "Rugoso da África" apresentaram maior produção de frutos de laranjeira "Folha Murcha".