Soil compaction limits maize and bean yields in precision agriculture zones under no-tillage system

Despite the benefits of no-till practices, soil compaction is a problem that can cause, among other things, mechanical impediment to root growth and less response to soil fertilization. The objective of this study was to evaluate the effect of subsoiling and doses of phosphate fertilization on soybean that have been cultivated over ten years under no-till systems in the Brazilian Cerrado. The experiment consisted of a randomized complete block design in a 2 × 4 factorial arrangement. Two managements in consolidated no-tillage area were considered: with and without subsoiling, along with four levels of phosphate fertilization: 0, 100, 300 and 400 kg ha-1 of P2O5. The practice of subsoiling in an area with ten years of no-till system provided an increase of 124.38 kg ha-1 in soybean productivity. Soybean plants grown under no-tillage system, with subsoil management, showed better development and pod production. The maximum phosphorus efficiency, with subsoiling, was achieved with the dose of 172 kg ha-1 of P2O5, yielding 5,693.4 kg ha-1. In the no-tillage system, the maximum efficiency dose and crop yield were 159 kg ha-1 of P2O5 and 5434.2 kg ha-1, respectively.

Deforestation and land-use effects on soil degradation and rehabilitation in western Nigeria. I. Soil physical and hydrological properties

Measurements of soil CO2 flux in the absence of living plants can be used to evaluate the effectiveness of soil management practices for C sequestration, but field CO2 flux is spatially variable and may be affected by soil compaction and the percentage of total pore space filled with water (%WFPS). The objectives of our study were: (i) to evaluate the effect of wheel traffic compaction on CO2 flux at two landscape positions with differing soil properties; and (ii) to examine the relationship of CO2 flux and %WFPS under field conditions and a wide range of soil porosities. Carbon dioxide flux was measured near Ames, IA, in a no-till system without living plants using the closed chamber method on nine cylinders inserted into the soil at each measurement site and evenly spaced across three rows, an untracked interrow, and a tracked interrow. Flux, volumetric water contents, and soil temperature were measured on 12 or 13 d between day of the year (DOY) 164 and 284 in 2001, 2004, and 2005. Bulk density, soil organic C concentration, and soil texture were determined after DOY 284. On most days, CO2 flux was less in the tracked interrow than in the row or untracked interrow positions. In all 3 yr, the cumulative flux of the tracked position was significantly less than one or both of the other positions. Landscape position did not affect the response of CO2 flux to traffic. Percentage water-filled pore space was not a good predictor of surface CO2 flux in the field. The effect of wheel traffic compaction on CO2 flux should be considered when soil CO2 flux is used to compare management practices.

O objetivo deste trabalho foi avaliar os efeitos da compactação do solo sobre suas propriedades morfoestruturais e sobre o desenvolvimento radicular da soja, sob sistema plantio direto, em um experimento conduzido num Latossolo Vermelho distroférrico, em Londrina, PR. O delineamento utilizado foi o de blocos ao acaso, com parcelas subdivididas e quatro repetições. Foram constituídos dois tratamentos de manejo nas parcelas: um em solo escarificado à profundidade de 20-25 cm, com densidade do solo de 1,17 Mg m-3; e outro em solo compactado, a 12 cm de profundidade, e densidade de 1,38 Mg m-3. Nas subparcelas, foram semeadas duas cultivares de soja, Embrapa-4 e BR-16. A presença de camadas mais compactas no perfil do solo provocou o desenvolvimento radicular em zonas de menor resistência, em poros biológicos e nas fissuras do solo. A produção de grãos não apresentou diferença entre os tratamentos, graças à adequada disponibilidade hídrica durante o período avaliado. A cultivar Embrapa-4 apresentou maior crescimento radicular em estruturas compactas, comparada à cultivar BR-16.

Mechanical and biological chiseling impacts on soil organic C stocks, root growth, and crop yield in a long-term no-till system

A compactação é um grave problema para a qualidade do solo e o desenvolvimento de uma agricultura sustentável, pois modifica os fluxos de água e ar no solo e reduz a produtividade das culturas agrícolas. Uma das alternativas para amenizar esse problema é o uso de espécies com sistema radicular profundo e vigoroso. O objetivo deste trabalho foi avaliar a qualidade física de um Argissolo Vermelho cultivado no sistema de plantio direto, após o cultivo de plantas de cobertura, e identificar o limite crítico de densidade do solo. No outono/inverno de 1999/00 e 2000/01, toda a área experimental foi cultivada com aveia-preta (Avena strigosa) mais ervilhaca (Vicia sativa) e, em 2001/02, com nabo forrageiro (Raphanus sativus). No verão, foi semeado milho (Zea mays) e, no final do ciclo, foram semeadas as plantas de cobertura de verão, crotalária juncea (Crotalaria juncea), guandu-anão (Cajanus cajan), mucuna-cinza (Stilozobium cinereum) e feijão-de-porco (Canavalia ensiformis), e comparadas ao pousio. Foram medidas a densidade e a resistência do solo à penetração. O sistema radicular das plantas foi avaliado pelo método do perfil radicular durante o ciclo do nabo forrageiro, do milho e das plantas de cobertura de verão. O plantio direto nesse Argissolo Vermelho eleva a densidade do solo para níveis considerados limitantes às plantas. Todas as culturas utilizadas nas rotações tiveram restrições de crescimento das raízes, e não foi possível observar diferenças entre as espécies no potencial de crescimento das raízes em solos compactados. O crescimento normal das raízes das plantas de cobertura ocorreu até o limite de densidade de 1,75 Mg m-3. Entre a faixa de 1,75 e 1,85 Mg m-3, ocorreu restrição, com deformações na morfologia das raízes em grau médio, e, acima de 1,85 Mg m-3, essas deformações foram significativas, com grande engrossamento, desvios no crescimento vertical e concentração na camada mais superficial. Todas as espécies avaliadas podem ser utilizadas em solos com algum grau de compactação, mas, quando a densidade for superior a 1,85 Mg m-3, pode ser necessária a mobilização do solo com escarificador e, ou, subsolador para facilitar a penetração das raízes em profundidade.

Soil physical and structural degradation may influence crop productivity over time in long-term no-tillage system areas. A field study was conducted at two sites, Palmeira das Missoes and Nao-Me-Toque, in southern Brazil to quantify soil physical/hydraulic and structural changes in zones with different yield potentials. The sites have been managed under no-tillage system without soil disturbance for more than 10 years. Soils were classified as Oxisols (Hapludox). Each site was divided into three zones with low, medium and high yield potentials based on overlapping of yield maps obtained from harvesters with precision agriculture tools. Within each yielding zone soil samples were collected to determine bulk density, porosity and aggregate stability. In addition, water infiltration rate and initial time for starting surface runoff were measured using a sprinkler infiltrometer (Cornell Sprinkler infiltrometer). Our findings showed that soils under low-yielding zones presented higher bulk density, lower macro-aggregate stability and water infiltration rate as well as shorter time for starting surface runoff compared to high-yielding zones. Therefore, these results suggest that soil physical and structural degradations have induced crop yield losses under long-term no-tillage areas. Macro-aggregate stability (>4.76 mm) and water infiltration rate were efficient parameters for distinguishing yielding zones in Oxisols managed under long-term no-tillage system in southern Brazil. Key words: Soil compaction, Cornell Sprinkler Infiltrometer, soil aggregation, water infiltration.

Buckwheat Species as Summer Cover Crops for Weed Suppression in No-Tillage Vegetable Cropping Systems

Agricultural fields are usually subjected to high amounts of traffic from field operations. The influence of traffic on sandy loam soil in three tillage systems were investigated in a field experiment. The field was located in a Canadian prairie region. In the experiment, the treatments were three tillage systems: no-tillage, disc tillage, and spring-tine tillage. Following tillage operations, field plots were trafficked with one pass of a sub-compact tractor. Soil properties were measured before and after the traffic to examine the effects of tillage systems and wheel traffic. For the effects of the tillage systems on the soil bulk density, soil shear strength, soil surface resistance, and soil cone index, the no-tillage system had higher values for all the soil properties when compared with the disc and spring-tine tillage systems. The plant (canola) population density ranged from 18.2 plants/m2 to 34.9 plants/m2, with the no-tillage having the lowest plant densities. For the effects of wheel traffic, one pass of the tractor in the disc and spring-tine tillage plots resulted in a 2.7% and 17.4% reduction in soil moisture content, respectively. After wheel traffic, the average soil shear strength for the disc and spring-tine systems were still significantly lower than the no-tilled system. Sinkages of 40 and 50 mm were observed for the spring-tine and disc tillage systems, respectively. The results of this study highlight the importance of preventing the demerits of soil compaction induced by wheel traffic after tillage operations.

In the global agribusiness, the herbicide use is a major problem for sustainable production, in this sense, it is necessary to better understand the interaction of weed species and floristic composition such as biodiversity indicators. The objective of this study was to analyze the spatial variability of weeds in an Oxisol under no-tillage system. Samples were taken in an area of 0.5 ha, in 50 sampling points with spacing of 5 m x 10 m. Data were analyzed by means of classical statistics, geostatistics, and spatial variability of the constructed maps by the interpolation by kriging technique. All the species of weeds presented in the study area showed spatial variability with the exception of Ipomoea triloba (L.) and Heliotropium indicum (L.), which showed pure nugget effect. The range values (a) shows that the spacing between samples can be extended to all species of weeds. The study was unable to determine specifics areas of management in the local since the different species of weed infested different plots of the area. Key words: Precision agriculture, semivariograms, site-specific management.

Experiments were begun in 1990 to determine the efficacy of using grassy and leguminous living mulches for asparagus (Asparagus officinalis L.) establishment and production. Ten-week-old seedlings of hybrid asparagus, cv. Syn4-56 were planted in loamy sand in the irrigated Central Sands of Wisconsin. Treatments were unsuppressed living mulches of perennial ryegrass (Lolium perenne L.), Dutch white clover (Trifolium repens L.), a mixture of ryegrass and clover, and a cultivated no-mulch control. A second variable, ammonium nitrate, banded at 40 and 80 lb N/acre, with a control of 0 lb N/acre, was factorially combined with mulch treatments. Asparagus fern growth with living mulches in year 1 was half that of asparagus grown with no mulch. Asparagus fern growth with clover and mixed mulches in year 2 averaged 75% of that grown without mulch. Fern growth with ryegrass mulch in year 2 was 50% of that grown with no mulch. Asparagus N uptake in clover and mixed mulch plots was as great as that grown with no mulch at each level of applied N. Weeds were controlled better by clover and mixed mulches than by ryegrass mulch or by cultivation in the no-mulch plots

Climate change necessitates a revised approach to crop cultivation technologies, prioritizing enhanced agricultural practices for soil conservation, water retention, and high-quality yields. To evaluate the influence of different soil tillage systems on yield and yield quality in spring cereals, a field experiment was conducted at the Agricultural Research and Development Station (ARDS) Turda. The experiment followed a split-plot design with two replications, within a 3-year rotation (soybean–spring cereals–maize). Three spring cereal species (wheat, two oat varieties, and barley) were tested under four tillage systems (plowing, chiseling, disking, and direct sowing) on Phaeozem soil with a clay-clay texture. The hectoliter weight (TW), thousand kernel weight (TKW), and grain protein content are influenced to some degree by the tillage system. The highest soil compaction levels were observed in the NT system, while the lowest were recorded in the CS system. High temperatures and drought led to notable soil moisture decreases in June and July, especially in the minimum tillage with disking (MTD) and NT systems. Tillage with plow and chisel resulted in lower bulk density values. Yields in the unconventional systems (minimum tillage with chisel (MTC) and MTD) were comparable to those in the conventional system (CS), indicating their viability as alternatives to traditional plowing. A yield reduction was noted in the no-tillage system.

Soil physical quality on tillage and cropping systems after two decades in the subtropical region of Brazil

O objetivo desse trabalho foi avaliar, em solo compactado, a estabilidade dos agregados influenciada pelo cultivo de espécies de cobertura em esquema de rotações de culturas, em sistema de semeadura direta, mediante o efeito da escarificação mecânica. As rotações de culturas repetidas por três anos consecutivos envolveram o cultivo de triticale e girassol, no outono-inverno, associados ao cultivo de milheto, de sorgo forrageiro e de Crotalária júncea como plantas de cobertura, antecedendo o da soja (cultura de verão). No tratamento envolvendo a escarificação mecânica, a área permaneceu em pousio entre os cultivos de outono-inverno e de verão. O experimento foi realizado na Fazenda Experimental Lageado (Botucatu-SP), nos anos agrícolas de 2003/2004, 2004/2005 e 2005/2006. O delineamento experimental foi o de blocos ao acaso, com quatro repetições, em esquema de parcelas subdivididas. As amostras para a análise da estabilidade de agregados foram coletadas nas profundidades de 0 a 0,05 m e de 0,05 a 0,10 m após o manejo das plantas de cobertura em dezembro de 2003 e de 2005. Logo no primeiro ano de instalação do experimento, o cultivo de triticale resultou em maior porcentagem de agregados com mais de 2 mm, maior DMG e maior DMP na camada de 0 a 5 cm, além de maior DMP na camada de 0,05 a 0,10 m. Já a escarificação do solo e a ausência do cultivo de plantas de cobertura proporcionaram menor porcentagem de agregados maiores que 2 mm e menor DMP na camada de 0,05 a 0,10 m. A estabilidade dos agregados foi influenciada pela rotação de culturas, sendo maior na camada de 0 a 0,05 m e de 0,05 a 0,10 m quando o triticale foi introduzido como espécie de outono-inverno.

O acúmulo de carbono orgânico (CO) observado em solos sob sistema de semeadura direta pode resultar em aumento de sua elasticidade, levando a maior resistência à compactação. Este estudo foi realizado para avaliar o efeito da umidade e do enriquecimento de CO sobre a elasticidade de dois solos, sendo um Nitossolo Vermelho distrófico latossólico e um Argissolo Vermelho-Amarelo distrófico arênico. Amostras superficiais de solo, coletadas no Argissolo e no Nitossolo, com variação significativa do teor de CO, foram equilibradas em quatro diferentes tensões de água e, então, submetidas a carregamentos e descarregamentos em uma prensa de compressão uniaxial, determinando-se o coeficiente de descompressão (Cd), o índice de recuperação do índice de vazios (Ir) e a redução da densidade (Re), após remoção das cargas aplicadas. Os resultados demonstram que o Ir variou de 11,4 a 16,4 % no Nitossolo e de 14 a 23,4 % no Argissolo, dependendo da tensão de água e do teor de CO da amostra. O teor de CO das amostras afetou significativamente o Cd e, conseqüentemente, a Re após a retirada das cargas. A Re média observada variou de 0,023 a 0,059 Mg m-3 e de 0,018 a 0,078 Mg m-3, respectivamente para o Argissolo e o Nitossolo. A elasticidade do solo é sensivelmente afetada pela variação no teor de água e de CO.