ABSTRACT Vast areas of the Brazilian Amazon have been deforested for the expansion of livestock and the agricultural frontier, which has resulted in soil exhaustion. It is therefore urgent to reduce deforestation and encourage sustainable land use to promote social and economic development in the region. The aim of this study was to evaluate the impact of different land use systems (an agroforestry system, cassava cultivation, non-degraded pasture, native forest) on the chemical properties of the soil (0-40 cm) in the mesoregion of the Juruá Valley, in the state of Acre, Brazil. Principal component analysis showed the soil in the forested area (reference) has greater values for P, Ca2+, Mg2+, K+, Na+, sum of bases, and cation exchange capacity; while hierarchical cluster analysis suggested little dissimilarity to the soil in the agroforestry system, and high dissimilarity to the soil in the areas of cassava cultivation and pasture. The results therefore support agroforestry as the most sustainable land use system, compared to cassava cultivation or pasture.

ABSTRACT State parks are integral protection units created to protect ecosystems. However, anthropic activities may have been previously performed before their creation, forming transitional areas. Studies that evaluate the modifications of edaphic properties in these environments are scarce. The aim of this study was to evaluate the changes in soil properties and litter stock in areas of eucalyptus-forest ecotones. Litter stock (Stocklitter) and total soil organic carbon content and stock (TOCsoil), weighted mean diameter (MWD), origin of aggregates (biogenic or physicogenic) and respective content of total organic carbon (TOCBio and TOCPhy), total organic carbon (TOCAG), soil organic matter chemical fractions [fulvic acid (FAC), humic (HAC), and humin (HUMC)], and particulate, mineral-associated, free light and intra-aggregate light (POC, MAOC, FLFC, and ILFC) soil organic matter, fertility, and glomalin-related soil protein (GRSP) fractions were evaluated in aggregates (layer 0.00-0.10 m) in areas of eucalyptus-forest ecotone (Eco), preserved forest fragment (For), and eucalyptus plantation (Euc), in Nova Baden State Park, Lambari–MG. In the Euc and Eco areas, the highest Stocklitter content was found. Higher values of TOCsoil, TOCAG, GRSP, and MWD were observed in the Euc area. In the biogenic aggregates, the highest content of TOCBio, HAC, HUMC, POC, MAOC, FLFC, and ILFC was determined in detriment of the physicogenic ones. The dynamics of edaphic properties in the Eco area showed greater similarity with the For area than in the Euc area. In general, all vegetation covers contribute to the maintenance of soil quality.

Resumo Experimentos de manipulação podem contribuir para a compreensão do papel ecológico da serapilheira em ecossistemas florestais. No entanto, há poucos estudos desta natureza. Os efeitos da remoção da camada de serapilheira (RS) foram avaliados sobre a comunidade de artrópodes do solo em dois plantios abandonados de Corymbia citriodora, em diferentes estágios de regeneração natural de espécies nativas de Mata Atlântica. Armadilhas de queda foram instaladas aleatoriamente em 5 parcelas (5 x 20 m) de RS e controle (CT), no plantio com 19 anos de idade (P19: estágio menos avançado; maior participação da serapilheira de eucalipto) e plantio com 42 anos (P42: estágio mais avançado de regeneração; maior participação da serapilheira de espécies nativas), nas estações chuvosa e seca, na Reserva Biológica União, RJ, Brasil. A maioria dos grupos taxonômicos apresentou inibição da abundância com a RS, no P19 e P42. De uma maneira geral, Diptera, Poduromorpha, Pseudoscorpionida, Symphypleona e larvas de Coleoptera foram os principais grupos impactados negativamente pela RS. Por outro lado, alguns grupos foram favorecidos pela RS, principalmente Entomobryomorpha e Formicidae. A RS diminuiu a riqueza total, uniformidade e diversidade de artrópodes edáficos em ambos os plantios. Contudo, este efeito negativo foi mais importante no P19, no qual também ocorreu a diminuição da abundância total e riqueza média. O maior fechamento do dossel provavelmente minimizou o impacto negativo da RS sobre os artrópodes edáficos no P42.

Abstract Manipulation experiments can contribute to understand the ecological role of litter in forest ecosystems. However, there are few studies of this nature. We evaluated the effects of the litter layer removal (RS) on the soil arthropod community in two abandoned plantations of Corymbia citriodora at different stages of the Atlantic Rainforest natural regeneration. Pitfall traps were randomly installed in plots (5 x 20 m) of RS and control (CT) in a 19-year old plantation (P19: less advanced stage of natural regeneration of Atlantic Rainforest species; higher contribution of eucalypt in litterfall) and a 42-year old plantation (P42: more advanced stage of regeneration; higher contribution of native species in litterfall), in rainy season and dry season at ‘União Biological Reserve’, RJ state, Brazil. RS inhibited the abundance of the most taxonomic groups, both in P19 and P42. In general, Diptera, Poduromorpha, Pseudoscorpionida, Symphypleona, and larvae of Coleoptera were the most negatively impacted groups by RS. In contrast, RS favored some other groups, principally Entomobryomorpha and Formicidae. Total richness, evenness and diversity were lower in RS in both plantations. However, this negative effect was stronger in the P19, where RS also decreased total abundance and average richness. The higher canopy closure probable minimized the negative impact of RS on the soil arthropods in P42.

RESUMO A ciclagem de nutrientes é influenciada pelo estágio sucessional. Contudo, existem divergências quanto ao padrão desta dinâmica. No presente estudo, objetivou-se avaliar os atributos químicos do solo superficial e da serapilheira produzida em dois plantios abandonados do eucalipto Corymbia citriodora em diferentes estágios de sucessão secundária de espécies nativas de Mata Atlântica (PJ: plantio jovem; PM: plantio maduro), na Reserva Biológica União, Rio de Janeiro. Testou-se a hipótese de que ocorre o incremento da concentração de nutrientes na camada superficial de solo e na serapilheira, da produção de serapilheira e do aporte de nutrientes para o solo via serapilheira, em função do avanço da sucessão. Em cinco parcelas (5 m x 20 m) em PJ e PM, foram realizadas amostragens da camada superficial do solo (0-10 cm; estações seca/2008, chuvosa/2008, seca/2009 e chuvosa/2010) e da serapilheira (coletores com 0,49 m2; 1,0 m acima do solo; coletas quinzenais; período amostral de 366 dias). A camada superficial do solo na área PM apresentou maiores concentrações de C e N totais, H+Al e Mn. Por outro lado, os valores de pH, razão C/N, concentrações de K, Fe e Zn foram maiores na camada de solo superficial na área PJ. Não se detectou padrão claro para as concentrações de P e Cu no solo. A produção anual de serapilheira foi maior na área PM, que apresentou maiores concentrações de N total e Mg, enquanto na área PJ foram verificados maiores valores da razão C/N e concentrações de P e Ca. Não houve variação para C total na serapilheira. Os aportes de C, N, P, K e Mg foram maiores na serapilheira na área PM, e não houve diferenças entre as áreas PJ e PM para o aporte de Ca. Corroboramos em parte a hipótese testada em relação ao teor de nutrientes na camada superficial do solo, serapilheira e aporte de nutrientes, e corroboramos integralmente a hipótese no que se refere à produção de serapilheira.

ABSTRACT The nutrient cycling is influenced by the successional stage. However, there is disagreement in relation to the pattern of this dynamic. The present study aimed to evaluate the chemical attributes of the topsoil and litterfall in two abandoned plantations of the eucalyptus Corymbia citriodora in different stages of Atlantic Rainforest succession (PJ: young plantation; PM: mature plantation) at the União Biological Reserve, RJ. We tested the hypothesis that there is an increase in the nutrient contents in the topsoil and litterfall, the amount of litterfall and nutrient input to the soil, as the process of forest succession advances. We sampled the topsoil (depth of 0-10 cm; dry season/2008, rainy season/2008, dry season/2009, rainy season/2010) and litterfall (0.49 m2 traps; 1.0 m above the forest floor; twice a month; 366 days) in five plots (5 m x 20 m) in the areas of PJ and PM. The topsoil in the PM area presented higher content of total C and N, H + Al, and Mn. On the other hand, the values of pH, C/N ratio and content of K, Fe, and Zn were higher in the topsoil in the PJ area. No clear pattern was detected in terms of the P and Cu content in the topsoil. The annual litterfall was higher in the PM area, which presented higher content of total N and Mg, while higher C/N ratio and content of both P and Ca occurred in the PJ area. We did not detect differences in terms of total C in litterfall. The input of C, N, P, K and Mg to the soil were higher by litterfall in the area of PM, and there were no differences between PJ and PM in relation to the Ca input. We partly corroborated the tested hypothesis in relation to the nutrient content in topsoil, litterfall and nutrient input, and we completely corroborated the hypothesis in terms of litterfall.

RESUMO Plantios de espécies florestais de interesse madeireiro contribuem para diminuir a pressão sobre a floresta amazônica, proporcionam o desenvolvimento sustentável na região e geram benefícios ecológicos. Este estudo objetivou avaliar a sobrevivência e o crescimento de quatro espécies nativas (Swietenia macrophylla, Parkia decussata, Dipteryx odorata e Jacaranda copaia) e uma exótica (Acacia mangium), em plantios monoespecíficos (espaçamento de 2 x 2 m) estabelecidos em áreas anteriormente ocupadas por pastagem, em Itacoatiara, Amazonas. Aos quatro anos de idade, foram obtidos dados biométricos [diâmetro à altura de 1,30 m do solo (DBH, cm), área de projeção de copa (CPA, m2), altura total (Ht, m), volume comercial do cilindro (Vcyl, m3 ha-1)], e dados qualitativos obtidos por diagnose visual [taxa de sobrevivência (S; %), estado nutricional (NS, G: bom; D: deficiente; %) e estado fitossanitário (PS, S: satisfatório; NS: não-satisfatório; %). Para cada espécie considerou-se três parcelas de 128 m2, cada uma com 32 plantas. Jacaranda copaia, seguida de Dipteryx odorata e Parkia decussata, foram as espécies mais recomendadas para o plantio em áreas com condições edafoclimáticas semelhantes às do presente trabalho, devido ao seu melhor desempenho para a maioria das variáveis.

ABSTRACT Planting of forest species of timber interest helps to reduce the deforestation pressure on the Amazon forest, promotes sustainable development of the producing region and generates ecological benefits. The objective of this work was to evaluate the survival rate and growth of four native (Swietenia macrophylla, Parkia decussata, Dipteryx odorata and Jacaranda copaia) and one exotic (Acacia mangium) species in monospecific plantations (spacing of 2 x 2 m) established on areas previously used for grazing, in Itacoatiara, State of Amazonas, Brazil. When the trees were four years old, we collected biometric data [height at 1.30 m (DBH, cm), crown projection area (CPA, m2), total height (Ht, m), commercial cylinder volume (Vcyl, m3 ha-1)], and qualitative data from visual diagnosis [survival rate (S, %), nutritional status (NS, G = good, D = deficient, %), and phytosanitary status (PS, S = satisfactory, N = non-satisfactory, %)]. Three plots of 128 m2, with 32 plants each, were evaluated for each species. Jacaranda copaia, followed by Dipteryx odorata and Parkia decussata, were the recommended species for planting in areas with edaphoclimatic conditions similar to those of the present work, due to their better performance according to most of the variables.

Abstract The stage of natural forest regeneration may influence soil fauna. This study aimed to test the hypothesis that there are differences in the structure and composition of the soil fauna communities between areas undergoing less advanced (LAS) and more advanced (MAS) stages of natural regeneration of Seasonal Semideciduous Forest at Pinheiral, RJ. Soil fauna was sampled using pitfall traps, during dry and rainy seasons. Total abundance, abundance of the saprophagous/predator group, mainly Formicidae, and the relative participation of Orthoptera were higher in MAS, while the relative participation of Acari, Araneae, Coleoptera, Diptera and the herbivorous group were higher in LAS, during both climatic seasons. Some taxonomic groups were restricted to one of the areas. Richness, evenness and diversity tended to present higher values in LAS (dry season). The higher complexity of the soil fauna community was correlated to the higher leaf litter standing stock in LAS.

ABSTRACT Restingas are extremely degraded, tropical sandy ecosystems and are poorly studied in terms of nutrient cycling. The present study aimed to evaluate litter dynamics in a forest dune at Restinga da Marambaia, RJ. Litterfall was collected monthly using two parallel transects installed 200 m apart from each other with 15 litter traps (0.25 m2), over two consecutive years. The litterfall was sorted into leaves, twigs, flowers, fruits, and refuse. Litter decomposition was evaluated by the ratio between litterfall and litter layer on the soil surface, which was estimated every four months by quadrats (0.25 m2) placed next to the litter traps. The average annual litterfall was low (6.8 t ha-1 year-1 ), mostly constituted by leaves (70%), with the greatest deposits occurring during the rainy season. The decomposition rate was low (0.85) and the turnover time was long (439 days). This litter dynamic contributes to the nutrient economy.

RESUMO. Plantios florestais podem mimizar o efeito do desmatamento na Amazônia. Contudo, há diferenças entre as espécies com relação à influência no solo. Os efeitos de plantações monoespecíficas de Acacia mangium, Dipteryx odorata, Jacaranda copaia, Parkia decussata e Swietenia macrophylla, e áreas de pastagem e mata nativa, sobre os atributos químicos do solo, foram avaliados na Amazônia brasileira. Uma amostra composta de solo por parcela foi coletada (0-5, 5-10 e 10-30 cm; três parcelas de 128 m2) em cada área. Não houve diferenças significativas para a maioria dos atributos avaliados, na comparação entre os plantios. Contudo maiores valores de K+ e P foram observados sob Swietenia macrophylla, enquanto maiores valores de Ca2+, soma de bases e pH ocorreram sob Jacaranda copaia. Em relação aos plantios, na mata nativa foram menores o pH e P disponível, enquanto conteúdo de matéria orgânica do solo (MOS), carbono orgânico do solo (COS), capacidade de troca catiônica (CTC), N, H+Al e Al3+ foram maiores. Sob pastagem, ocorreram menores valores de MOS, COS, CTC, K+, Mg2+, N, H+Al e Al3+. Não ocorreu o retorno das condições originais dos atributos químicos do solo observados na mata nativa, sob nenhuma espécie florestal. No entanto, os plantios de S. macrophylla e J. copaia promoveram as maiores influências positivas no solo.

ABSTRACT. Forest plantations may minimize the effects of deforestation in the Amazon. However, there are differences among species in terms of their influences on soil recovery. The effects of monospecific plantations of Acacia mangium, Dipteryx odorata, Jacaranda copaia, Parkia decussata,and Swietenia macrophylla, and areas of pasture and native forest on the chemical soil attributes of the Brazilian Amazon were evaluated. One bulked soil sample was collected per plot (0.00-0.05, 0.05-0.10, and 0.10-0.30 m; three plots of 128 m2) in each area. No significant differences in most of the soil attributes were observed among the forest plantations. However, soil K+ and P were higher in the Swietenia macrophylla plantations, while higher values of Ca2+, sum of bases, and pH occurred in Jacaranda copaia plantations. In the native forest, the pH, and P content were lower, whereas the soil organic matter (SOM) content, soil organic carbon (SOC) content, cation exchange capacity (CEC), N content, H+Al content, and Al3+ content were higher than in the plantations. The lowest values of SOM, SOC, CEC, K+, Mg2+, N, H+Al, and Al3+ occurred in the pasture. None of the forest species led to the return of the original soil chemical attributes of the native forest. However, S. macrophylla and J. copaia plantations presented the highest positive edaphic influences.

RESUMO Atualmente, há poucas informações sobre a recuperação de áreas onde ocorre a extração de piçarra na Caatinga. Objetivou-se avaliar o emprego da fauna edáfica como bioindicadora da qualidade do solo em áreas com e sem a adição de topsoil (CT e ST, respectivamente), em plantios florestais para a recuperação de áreas de extração deste recurso mineral. Considerou-se a mata nativa de Caatinga (MT) como referencial. Foram instaladas 10 armadilhas em três réplicas para cada tratamento, em delineamento em blocos casualizados em esquema de parcelas subdivididas, no final da estação chuvosa,em diferentes épocas (0, 1, 3 e 6 anos depois). Capturou-se um total de 45.740 organismos, distribuídos em 36 grupos taxonômicos, com o predomínio de Acari, Diptera, Entomobryomorpha, Formicidae, Poduromorpha e Symphypleona, em todos os tratamentos (ST, CT, MT). Nove grupos (25% do total) apresentaram ocorrência restrita. Os valores de riqueza e diversidade foram maiores na MT, seguidos do CT e ST. Não houve um padrão definido para a uniformidade e abundância total da comunidade. A maioria dos grupos apresentou inibição na abundância nos tratamentos testados em relação à MT, mas este efeito negativo foi relevante no ST, em comparação com o CT. A similaridade entre ST e CT foi elevada, e muito baixa com a MT. A complexidade ecológica da comunidade da fauna edáfica foi maior na MT. A fauna edáfica funcionou como bioindicadora da qualidade do solo, que foi maior em CT, na comparação com ST.

ABSTRACT Information on the recovering of areas of gravel extraction of the Caatinga biome are scarce. Thus, the objective of this work was to assess the soil fauna as bioindicator of soil quality, evaluating areas with addition of topsoil (WAT) and control areas (CWT) without the addition of topsoil used for forest plantations, which were implemented for recovering gravel extraction areas. A native forest of the Caatinga biome (NFC) was taken as a reference. Ten traps with three replicates were installed in each area, which were evaluated in a randomized block design in split-plot arrangement at the end of the rainy season of different years, 0, 1, 3 and 6 years after the experiment implementation. A total of 45,740 specimens were captured. These specimens were from 36 taxonomic groups. The Acari, Diptera, Entomobryomorpha, Formicidae, Poduromorpha and Symphypleona were the predominant groups in all areas (WAT, CWT and NFC). Nine groups (25% of the total) had restricted occurrence. The fauna richness and diversity were higher in the NFC, followed by the WAT and CWT. The uniformity and total abundance of the soil fauna community showed no defined patterns. The abundance of most groups was inhibited in the treatments evaluated, compared with NFC, however, this adverse effect was more significant in CWT compared with WAT. The CWT and WAT had high similarity and both had very low similarity with NFC. The ecological complexity of soil fauna community was higher in NFC. The soil fauna was efficient as a bioindicator of soil quality, which was higher in WAT, compared with CWT.

ABSTRACT Inoculation with arbuscular mycorrhizal fungi (AMF) is a strategy to improve the efficiency of forest plantations, reducing costs and increasing the survival of plant species. The objective of this study was to assess the response and mycorrhizal dependency of seedlings of the forest species Apuleia leiocarpa (Vogel) J.F. Macbr to inoculation with AMF. The experiment was conducted in a completely randomized design using a 5 × 5 factorial arrangement with six replications. The treatments consisted of combinations of five P rates (0, 24, 71, 213, and 650 mg kg-1) with five types of inoculations with AMF (inoculation with the fungi Rhizophagus clarus, Gigaspora margarita, Dentiscutata heterogama, inoculation with an AMF mix of these three species, and a treatment without inoculation). The A. leiocarpa showed the highest biomass accumulations in inoculation with D. hetorogama combined with the P rates of 213 and 650 mg kg-1, and in the AMF mix combined with the P rates of 71, 213, and 650 kg-1. Biomass accumulation showed a linear, positive response to inoculation with D. heterogama combined with the different P rates, and a positive square root fit to inoculation with the AMF mix. The plants inoculated with G. margarita had no significant biomass accumulation. The plant species had a positive response to inoculation with R. clarus combined with the lowest P rates; however, it had a negative response to combination with the highest P rate (650 mg kg-1). The relative benefit of inoculation with these fungi was more than 100 % in most treatments, showing the high mycorrhizal dependency of A. leiocarpa and the nutritional benefit of AMF inoculation for this species. However, this response is dependent on the fungus species that colonize the plant roots. The best combination between fungus and P rate was inoculation with the AMF mix combined with the P rate of 71 mg kg-1.

ABSTRACT This study aimed to test the effects of fertilization with organic compost from industrial production of pulp on the litterfall and nutrient input of monospecific plantations in a loan area. The treatments consisted of three doses of the organic compost D10, D15 and D20 (10, 15 and 20 Mg ha-1, respectively), mineral conventional fertilization (DAM) and no fertilization (D0) in land plots (N = 4/treatment/species; 15 x 12 m). Litterfall was monthly collected by two traps (0.72 m2/plot) and sorted out into leaves, twigs, seeds, flowers, fruits and others. We determined the input of nitrogen, phosphorous and potassium. There were no differences among the treatments and between species in terms of total annual litterfall. The higher nutrient input was obtained by DAM, followed by D10, in both plantations. The annual nutrient input was higher for the litterfall on the E. urograndis plantation.

RESUMO O presente estudo objetivou avaliar a ocorrência de fungos micorrízicos arbusculares (FMA) em dois fragmentos florestais (FF 1 e FF 2) de Restinga periodicamente inundável, dispostos em um gradiente de saturação hídrica do solo em Marambaia, RJ. Em cada área foram coletadas amostras da camada superficial (0-5 cm), para avaliação da comunidade de FMA e dos atributos do solo. Entre as seis espécies de FMA encontradas, cinco foram comuns a ambas as áreas e Acaulospora scrobiculata se restringiu a FF 1. Acaulospora e Glomus foram os gêneros mais adaptados às condições ambientais dos ecossistemas. Não houve diferença significativa entre os fragmentos quanto à riqueza de espécies de FMA. Contudo, a abundância de esporos foi maior no FF 1. Parte destes resultados pode ser um reflexo dos menores valores de P disponível, teor de água e temperatura do solo no FF 1, quando comparado ao FF 2.

ABSTRACT The present study aimed to evaluate the arbuscular mycorrhizal fungi (AMF) ocurrence in two forest fragments (FF 1 and FF 2) of periodically floodable Restinga, arranged in a gradient of soil water saturation at Marambaia, RJ. Soil samples were collected at a depth of 0-5 cm to evaluate the AMF community and soil atributes. Six AMF species were found, five of them occurred in both areas and Acaulospora scrobiculata were restricted to FF 1. Acaulospora and Glomus were the best-adapted genus to the ecosystem conditions. There was no significant difference between the forest fragments in relation to the species richness. However, spores abundancy was higher in FF 1. Some of these results were influenced by lower values of availability of P, moisture content and temperature in soil at FF 1, in relation to FF 2.

RESUMO. A retranslocação interna é um importante mecanismo de conservação de nutrientes nas plantas, que depende de diferentes fatores. Contudo, ainda são incipientes os dados desta natureza, principalmente para espécies florestais tropicais. O presente trabalho objetivou avaliar a dinâmica de retranslocação de macronutrientes e a influência dos grupos ecológico (P: pioneiras x NP: não-pioneiras) e fenológico (ND: não-decíduas x D: semidecíduas / decíduas) nas concentrações foliares de macronutrientes em cinco espécies arbóreas em monocultivo na Amazônia brasileira: Acacia mangium Willd., Parkia decussata Ducke, Dipteryx odorata (Aublet) Willd., Jacaranda copaia (Aubl.) D. Don e Swietenia macrophylla King. Para tanto, foram coletadas folhas verdes fotossinteticamente ativas e folhas da serapilheira. A retranslocação foi estimada segundo a equação de Attiwill, Guthrie e Leuning (1978). As espécies pioneiras apresentaram maiores concentrações foliares de N; as não-pioneiras apresentaram maiores concentrações de K, Ca e S; e os resultados foram inconclusivos para P e Mg. As concentrações foliares de K e de P foram maiores nas espécies decíduas, enquanto que as de N, Ca, Mg e S foram praticamente idênticas entre os grupos fenológicos. No geral, as espécies pioneiras e as não-decíduas foram mais eficientes na retranslocação de nutrientes.

ABSTRACT. Internal retranslocation is an important mechanism for nutrient conservation in plants, which depends on different factors. However, there are little data about this subject, especially on tropical forest species. This study aimed to evaluate the macronutrient retranslocation dynamic and the influence of ecological (P: pioneer x NP: non-pioneer) and phenological (ND: non-deciduous x D: semideciduous / deciduous) characteristics on the macronutrient content of leaves of five tree species on monospecific plantations in the Brazilian Amazon: Acacia mangium Willd., Parkia decussata Ducke, Dipteryx odorata (Aublet) Willd., Jacaranda copaia (Aubl.) D. Don and Swietenia macrophylla King. Photosynthetically active green leaves and senescent leaves (leaf litter) were collected. Retranslocation was estimated through an equation proposed by Attiwill, Guthrie and Leuning (1978). The pioneer species presented higher foliar contents of N; the non-pioneer species presented higher contents of K, Ca and S; and the results were inconclusive for P and Mg. The deciduous species presented higher foliar contents of K and of P, whereas the foliar contents of N, Ca, Mg and S were virtually identical between the phenological groups. The internal retranslocation of foliar nutrients in pioneer and non-deciduous species was higher than that of non-pioneer and deciduous species.

O intervalo hídrico ótimo (IHO) é um método que integra vários fatores que afetam o desenvolvimento das plantas, e corresponde ao intervalo de umidade do solo no qual não ocorre restrição de aeração (porosidade de aeração mínima de 0,10 m³ m-3) nem de resistência mecânica à penetração das raízes (RP) dentro da faixa de água disponível às plantas, isto é, entre a capacidade de campo (CC) e o ponto de murcha permanente (PMP). O objetivo deste trabalho foi determinar o IHO em um Latossolo Vermelho sob plantio direto (PD) e plantio direto escarificado (PDE), bem como o rendimento de grãos de soja. Avaliou-se a densidade do solo, o IHO, a variação da umidade do solo durante o ciclo da soja e o rendimento de grãos. Os resultados indicaram que a densidade do solo foi menor no PDE, o que acarretou maior amplitude do IHO. A densidade crítica, na qual IHO = 0, foi semelhante entre o PD e o PDE. Durante o ciclo da cultura da soja, em vários momentos, a sua umidade ficou fora do IHO, quando assumida RP limitante de 2 MPa. Como o rendimento de grãos da soja não apresentou diferença significativa, deduz-se que a RP de 2 MPa não é limitante para a soja.

The least limiting water range (LLWR) was used to determine several factors that influence plant growth. The LLWR is defined as the water content range in which aeration (AFP) and soil resistance to root penetration (RP) are not restrictive, within the field capacity (FC) and permanent wilting point (PWP). The aim of the present study was to determine the LLWR and soybean grain yield in an Oxisol under non-tillage (NT) and chiseled no-tillage (CNT) systems. The soil density, LLWR, soil water content range throughout the soybean crop cycle and grain yield were assessed. Soil density was lower in the CNT system, which resulted in a wider LLWR. Critical density (LLWR=0) was similar in the NT and CNT systems. The soil water content decreased to values outside the LLWR at different periods during the crop cycle when a limiting RP of 2 MPa was considered. It was concluded that an RP of 2 MPa is not limiting for soybean because there were no significant differences in grain yield between the two tillage systems.

O plantio direto (PD) é, comprovadamente, uma técnica de manejo do solo eficiente no controle à erosão, minimizando as perdas de solo. No entanto, o não-revolvimento do solo, aliado ao tráfego de máquinas, acarreta alterações na sua estrutura que, associada à reduzida rugosidade superficial, podem ser desfavoráveis à infiltração de água, modificando a sua dinâmica nesse sistema. O objetivo deste trabalho foi avaliar as alterações nas propriedades físico-hídricas do solo sob PD e plantio direto escarificado (PDE), após seis anos sob PD, e os efeitos de sulcadores de semeadoras-adubadoras no solo. Avaliaram-se a densidade do solo, a porosidade total, a macroporosidade e a infiltração da água no solo antes da semeadura da soja, a rugosidade superficial e o percentual da superfície do solo coberto com restos culturais antes e depois da semeadura e a condutividade hidráulica do solo saturado após 12 meses da escarificação. O PDE apresentou uma densidade do solo menor que o PD e uma maior infiltração de água, condutividade hidráulica do solo saturado e rugosidade superficial, demonstrando ser uma técnica eficaz para melhorar a conservação do solo e da água, apresentando efeito residual da escarificação transcorrido um ano da operação. A porosidade total e a macroporosidade não apresentaram diferença significativa entre os manejos. Nos dois manejos, a cobertura do solo apresentou-se similar antes da semeadura, isto é, após seis meses da escarificação. Durante a semeadura da soja, os mecanismos sulcadores de adubo apresentaram ação distinta, tendo o tipo guilhotina incorporado significativamente mais restos culturais do que o duplo disco.

No tillage (NT) is a proven and efficient soil management practice used to reduce soil erosion, minimizing soil losses. However, the absence of soil movement associated with traffic of heavy machinery cause changes in the soil structure, which combined with low surface roughness, can affect water dynamics by reducing the water infiltration rate. Our aim was to evaluate changes in soil properties under NT and chiseling in no tillage (CNT), as well as the effect of distinct planter furrow openers on soil characteristics. The following parameters were assessed: bulk and particle density, total porosity, macroporosity, water infiltration into soil prior to soybean planting, surface roughness, percentage of soil surface covered with crop residues before and after planting, and soil hydraulic conductivity after 12 months of chiseling. CNT showed a lower soil density than NT, higher water infiltration, higher saturated soil hydraulic conductivity, and higher surface roughness. Therefore, CNT improved soil and water conservation since there were still residual effects one year after chiseling. Total porosity and macroporosity did not differ significantly between the soil management systems. Soil cover was similar under both managements before planting, i.e., six months after chiseling; however, at soybean planting, the hoe-type planter provided better incorporation of crop residues into the soil than the double-disc type.