Residual effects of composted sewage sludge on nitrogen cycling and plant metabolism in a no-till common bean-palisade grass-soybean rotation.

Introduction and aims: In the context of increasing population and decreasing soil fertility, food security is one of humanity's greatest challenges. Large amounts of waste, such as sewage sludge, are produced annually, with their final disposal causing environmental pollution and hazards to human health. Sludge has high amounts of nitrogen (N), and, when safely recycled by applying it into the soil as composted sewage sludge (CSS), its residual effect may provide gradual N release to crops. A field study was conducted in the Brazilian Cerrado. The aims were to investigate the residual effect of successive applications of CSS as a source of N in the common bean (Phaseolus vulgaris L. cv. BRS Estilo)-palisade grass (Urochloa brizantha (A.Rich.) R.D. Webster)-soybean (Glycine max L.) rotation under no-tillage. Additionally, N cycling was monitored through changes in N metabolism; the efficiency of biological N2 fixation (BNF) and its implications for plant nutrition, development, and productivity, was also assessed. Methods: The experiment consisted of a randomized complete block design comparing four CSS rates (10, 15, 20, and 25 Mg ha-1, wet basis) to a control treatment (without adding mineral or organic fertilizer) over two crop years. Multiple plant and soil analyses (plant development and crop yield, Falker chlorophyll index (FCI), enzymatic, biochemical, 15N natural abundance, was evaluated, root and shoot N accumulation, etc.) were evaluated. Results and discussion: Results showed that CSS: i) maintained adequate N levels for all crops, increasing their productivity; ii) promoted efficient BNF, due to the stability of ureide metabolism in plants and increased protein content; iii) increased the nitrate content and the nitrate reductase activity in soybean; iv) affected urease activity and ammonium content due to changes in the plant's urea metabolism; v) increased N accumulation in the aerial part of palisade grass. Composted sewage sludge can be used as an alternative source to meet crops' N requirements, promoting productivity gains and N cycling through forage and improving N metabolism.

Soil physicochemical and biological properties in soybean areas under no-till Systems in the Brazilian Cerrado.

No-till (NT) as a conservation practice aims to minimize soil disturbance and enhance soil sustainability. However, how NT practice affects soil physicochemical and biological properties in soybean areas remains unclear. This study selected 65 high-yielding soybean farms under a long-term NT system in the Brazilian Cerrado and collected soil samples at 0.0-0.10 m (L1), 0.10-0.20 m (L2) and 0.20-0.40 m (L3) depths. The effect of NT on soil properties and interactions with soybean productivities were assessed. Results showed that the average soybean yield of the study areas in the last three years was 4.13 Mg ha-1, with 26 areas presenting yields over 4.20 Mg ha-1. Most studied soil properties showed a depth stratification and were strongly concentrated in L1, except for S, Al3+ and aluminum saturation, which displayed lower surface and higher subsurface concentrations. Moreover, a high proportion of SOM is composed of light SOM fraction in areas of high soybean yield, with the average SOM values of 39.9, 27.8 and 19.6 g kg-1 in L1, L2 and L3, respectively. Soils under long-term NT present moderate values of enzyme activity compared with the relatively low values under conventional tillage system, especially 94 % of the plots have moderate values of activity of arylsulfatase enzymes. The data presented support the conclusion that NT system can enhance soil fertility and biological quality in soybean cultivation. Our results suggest that it is necessary to adopt NT practice because it allows increasing soybean productivity in Brazil without the need to increase the sown area, in addition to increasing productivity associated with an improvement in the agroecosystem quality, thus moving toward a more sustainable agriculture.

Dynamics and weed control effectiveness of dicamba herbicide when applied directly on the soil and corn straw in Brazil.

Dicamba is a post-emergence herbicide commonly used to control broadleaves in cereal crops. However, a portion of the herbicide might reach soil surface, and many factors could affect its dynamics and effects. The objective of this research was to evaluate the dynamics of dicamba applied to the soil, to the soil and covered with straw and over the straw, in addition, to evaluate the weed control in pre-emergence. Two field experiments at different locations were conducted with dicamba. To quantify dicamba in the soil a LC-MS/MS system was used. In both experiments, rainfall and straw played a key role in dicamba soil dynamics and weed control. Dicamba in the soil was affected by presence of straw and accumulated rainfall after the application. Higher concentrations (254-432 ng g soil-1) in the soil 0-10 cm layers and greater leaching potential were found for the application in the soil compared to over the straw. The maximum concentration of dicamba (101.6-226 ng g soil-1) was found after 10 mm of rainfall for dicamba application over the straw. Around 60-70% of weeds were controlled with concentrations greater than 20 ng/g soil-1, in the presence or absence of straw.

Efecto de los cultivos de cobertura invernales sobre el microbioma del suelo: revisión sistemática de la literatura / Effect of winter cover crops on the soil microbiome: a systematic literature review

Resumen La inclusión de cultivos de cobertura invernales (CCI) en un sistema de siembra directa (SD) en reemplazo del barbecho constituye una alternativa promisoria para mejorar la salud del suelo y contribuir a la sustentabilidad ambiental de los sistemas agrícolas. Esta revisión ofrece un panorama integral de los efectos sobre el microbioma del suelo que tiene la introducción de CCI en rotación con cultivos de verano en sistemas de SD vs. el barbecho desnudo. Se realizó una búsqueda sistemática de la literatura que reporta los efectos de los CCI sobre los parámetros de abundancia, actividad y diversidad microbiana del suelo. Combinando 7 criterios de búsqueda se seleccionaron y analizaron 22 trabajos. El conjunto de resultados de esos trabajos muestra que la actividad enzimática del suelo se ve favorecida con la inclusión de CCI en la rotación, principalmente si estos se componen de leguminosas y mezclas de especies. Más de la mitad de esos trabajos reportan una mayor biomasa microbiana con CCI que con barbecho. Además, se advierte que los efectos de los CCI sobre los parámetros microbianos son independientes de la duración de los ensayos. Sin embargo, aún se necesitan más investigaciones básicas que permitan reducir la heterogeneidad entre estudios y comprender las complejas interacciones que ocurren entre los CCI y el microbioma del suelo.

Abstract The inclusion of winter cover crops (WCC) in no-till (NT) systems in replacement of bare fallow is a promising alternative to improve soil health and consequently, contribute to environmental sustainability of agricultural systems. This review provides a comprehensive evaluation of the effects of the use of WCC in rotation with summer cash crops under NT systems on the soil microbiome versus bare fallows. A systematic literature search was conducted to evaluate the impact of WCC on microbial parameters indicative of abundance, activity and diversity. Twenty-two papers were selected based on seven combined criteria. The results of this review show that enzyme activities in soil are enhanced with the inclusion of WCC in the rotation, particularly those that include legumes and mix of species. ln general, more than half of the analyzed papers report higher microbial biomass in soils with WCC than in bare fallow. Interestingly, the effects of WCC on microbial parameters are independent of the duration of the experiments. However, more basic research is necessary to reduce the heterogeneity of the studies and to better understand the complexity of the interactions between WCC and the soil microbiome.

[Effect of winter cover crops on the soil microbiome: a systematic literature review]. / Efecto de los cultivos de cobertura invernales sobre el microbioma del suelo: revisión sistemática de la literatura.

The inclusion of winter cover crops (WCC) in no-till (NT) systems in replacement of bare fallow is a promising alternative to improve soil health and consequently, contribute to environmental sustainability of agricultural systems. This review provides a comprehensive evaluation of the effects of the use of WCC in rotation with summer cash crops under NT systems on the soil microbiome versus bare fallows. A systematic literature search was conducted to evaluate the impact of WCC on microbial parameters indicative of abundance, activity and diversity. Twenty-two papers were selected based on seven combined criteria. The results of this review show that enzyme activities in soil are enhanced with the inclusion of WCC in the rotation, particularly those that include legumes and mix of species. In general, more than half of the analyzed papers report higher microbial biomass in soils with WCC than in bare fallow. Interestingly, the effects of WCC on microbial parameters are independent of the duration of the experiments. However, more basic research is necessary to reduce the heterogeneity of the studies and to better understand the complexity of the interactions between WCC and the soil microbiome.

Impacts of switching tillage to no-tillage and vice versa on soil structure, enzyme activities and prokaryotic community profiles in Argentinean semi-arid soils.

The effects of tillage on soil structure, physiology and microbiota structure were studied in a long-term field experiment, with side-to-side plots, established to compare effects of conventional tillage (CT) vs no-till (NT) agriculture. After 27 years, part of the field under CT was switched to NT and vice versa. Soil texture, soil enzymatic profiles and the prokaryotic community structure (16S rRNA genes amplicon sequencing) were analyzed at two soil depths (0-5 and 5-10 cm) in samples taken 6, 18 and 30 months after switching tillage practices. Soil enzymatic activities were higher in NT than CT, and enzymatic profiles responded to the changes much earlier than the overall prokaryotic community structure. Beta diversity measurements of the prokaryotic community indicated that the levels of stratification observed in long-term NT soils were already recovered in the new NT soils 30 months after switching from CT to NT. Bacteria and Archaea OTUs that responded to NT were associated with coarse soil fraction, soil organic carbon and C cycle enzymes, while CT responders were related to fine soil fractions and S cycle enzymes. This study showed the potential of managing the soil prokaryotic community and soil health through changes in agricultural management practices.

Management of white mold of soybean using winter cereal straw / Manejo do mofo-branco na cultura da soja pelo uso de cobertura do solo com cereais de inverno

The management of white mold (Sclerotinia sclerotiorum (Lib.) De Bary) has been one of the main production limitations faced by soybean (Glycine max L.) producers. Considering the complex management of this disease and resistance structure of the pathogen, the present study was conducted in the municipalities of Guarapuava and Palmas in Paraná with the objective of managing the white mold of soybean using straws of winter cereals, such as oat, rye, and triticale. Initially, the three winter cereals were cultivated simultaneously in both the study areas. Straw production, plant height, and shoot fresh and dry weight were evaluated. Subsequently, BMX Apollo soybean was cultivated on cereal straws, and the incidence and severity of white mold were evaluated. In the in vitro experiment, 20 sclerotia covered by a layer of cereal (oat, rye, and triticale) straws were added and carpogenic germination was observed only in the control treatment after 98 days. Regardless of the study site, rye presented greater height and fresh weight than the remaining two cereals. Soybean cultivation on winter cereal straw reduced the incidence and severity of white mold. Cultivation on rye straw reduced mold incidence by 77.7% and 76.6% in Palmas and Guarapuava, respectively.(AU)

O manejo do mofo branco (Sclerotinia sclerotiorum) tem sido um dos principais limitantes de produção enfrentados por produtores de soja. Tendo em vista a complexidade do manejo desta doença e da estrutura de resistência do patógeno, o presente trabalho foi conduzido nos municípios de Guarapuava e Palmas - Paraná visando o manejo do mofo branco na cultura da soja utilizando palhadas de cereais de inverno, aveia, centeio e triticale. Inicialmente, cultivou-se os diferentes cereais de inverno, simultaneamente, nas duas áreas de estudo (Guarapuava e Palmas - PR). Avaliou-se a produção de palhada, a altura de plantas, a massa verde e seca da parte aérea. Posteriormente, semeou-se soja BMX Apolo sobre as palhadas de cereais e avaliou-se a incidência e a severidade do mofo branco. No experimento in vitro, adicionou-se 20 escleródios cobertos por uma camada de palhas (aveia, centeio e triticale) e após 98 dias, observou-se germinação carpogênica somente no tratamento testemunha. Independentemente do local de estudo, o centeio destacou-se com maiores altura e massa verde. O cultivo sobre palhada de cereais de inverno reduziu a incidência e severidade de mofo branco com destaque para a palhada de centeio, reduzindo a incidência da doença em 77,7% e 76,6%, em Palmas e Guarapuava, respectivamente.(AU)

Management of white mold of soybean using winter cereal straw / Manejo do mofo-branco na cultura da soja pelo uso de cobertura do solo com cereais de inverno

ABSTRACT: The management of white mold (Sclerotinia sclerotiorum(Lib.) De Bary) has been one of the main production limitations faced by soybean (Glycine max L.) producers. Considering the complex management of this disease and resistance structure of the pathogen, the present study was conducted in the municipalities of Guarapuava and Palmas in Paraná with the objective of managing the white mold of soybean using straws of winter cereals, such as oat, rye, and triticale. Initially, the three winter cereals were cultivated simultaneously in both the study areas. Straw production, plant height, and shoot fresh and dry weight were evaluated. Subsequently, BMX Apollo soybean was cultivated on cereal straws, and the incidence and severity of white mold were evaluated. In the in vitro experiment, 20 sclerotia covered by a layer of cereal (oat, rye, and triticale) straws were added and carpogenic germination was observed only in the control treatment after 98 days. Regardless of the study site, rye presented greater height and fresh weight than the remaining two cereals. Soybean cultivation on winter cereal straw reduced the incidence and severity of white mold. Cultivation on rye straw reduced mold incidence by 77.7% and 76.6% in Palmas and Guarapuava, respectively.

RESUMO: O manejo do mofo branco (Sclerotinia sclerotiorum) tem sido um dos principais limitantes de produção enfrentados por produtores de soja. Tendo em vista a complexidade do manejo desta doença e da estrutura de resistência do patógeno, o presente trabalho foi conduzido nos municípios de Guarapuava e Palmas - Paraná visando o manejo do mofo branco na cultura da soja utilizando palhadas de cereais de inverno, aveia, centeio e triticale. Inicialmente, cultivou-se os diferentes cereais de inverno, simultaneamente, nas duas áreas de estudo (Guarapuava e Palmas - PR). Avaliou-se a produção de palhada, a altura de plantas, a massa verde e seca da parte aérea. Posteriormente, semeou-se soja 'BMX Apolo' sobre as palhadas de cereais e avaliou-se a incidência e a severidade do mofo branco. No experimento in vitro, adicionou-se 20 escleródios cobertos por uma camada de palhas (aveia, centeio e triticale) e após 98 dias, observou-se germinação carpogênica somente no tratamento testemunha. Independentemente do local de estudo, o centeio destacou-se com maiores altura e massa verde. O cultivo sobre palhada de cereais de inverno reduziu a incidência e severidade de mofo branco com destaque para a palhada de centeio, reduzindo a incidência da doença em 77,7% e 76,6%, em Palmas e Guarapuava, respectivamente.

Phosphorus loss index for conservation agriculture systems in Southern Brazil: A new approach to environmental risk assessment.

The transport of phosphorus (P) from agricultural fields to watercourses is a worldwide concern. Development of tools to evaluate the environmental P risk is required to assist farmers and field technicians to recommend best management practices. The objective of this work was to develop and test a new approach to assess P loss vulnerability for agricultural conservationist systems in southern Brazil using easily obtainable soil attributes: cover crop residue (CCR), soil organic carbon (OC), visual evaluation of soil structure (VESS), soil test P (STP) and clay content. For that, the principal component analysis was applied, and simulated rainfall was conducted in ten agricultural fields with three replicates under Oxisol, with slopes from 7% to 12%. The database was separated into main and test groups. Significant principal components were correlated with runoff coefficient (RC), final infiltration rate (FIR), total sediment (TS), total P (TP), particulate P (PP), soluble P (SP) and bioavailable P (BAP). Component 1, interpreted as 'increased risk of PP transport', explained 49% of the variation with a strong dependence on CCR, OC, STP and VESS, and correlated with decreased FIR, and increased RC, TS, PP and TP. Component 2, interpreted as 'increased risk of SP transport', explained 21% of the variation with a strong dependence on OC, STP and clay content, and correlated with decreased TS, and increased SP and BAP. The P-index scores from components 1 and 2 were divided into four classes of P loss vulnerability (low, medium, high and very high) considering the first, median and third quartile. The Euclidean distances demonstrated a high similarity of the P-index scores obtained for the main and test groups. Therefore, the developed model can estimate the risk of P loss in agricultural fields with conservative management and moderate slope in conditions similar to the database.

Distribuição de raízes, resistência tênsil e friabilidade de agregados em solo com diferentes sistemas de manejo / Root distribution, tensil resistance and friability of aggregates in soil with different management systems

A qualidade estrutural do solo é desejável para o crescimento das plantas, assim como estabelecimento do sistema radicular. Diante disso, o objetivo do trabalho foi avaliar a distribuição de raízes, resistência tênsil e a friabilidade de agregados em solo com diferentes sistemas de manejo na cultura da soja. O delineamento experimental foi constituído em esquema fatorial 2 x 2 x 2, sendo fator A: Plantio Direto (PD) e Plantio Direto Escaficado (ESC); fator B: com e sem aplicação de gesso agrícola e fator C: com e sem utilização da haste sulcadora, dispostos em blocos ao acaso com três repetições. No estádio R2 da soja, foi realizada a coleta de solo para avaliação do sistema radicular nas profundidades de 0,0-0,05, 0,05-0,10, 0,10-0,20, 0,20-0,40e 0,40-0,60m, sendo que os valores de diâmetro (mm) e comprimento (cm).A escarificação do solo seguida pela utilização da haste sulcadora, ocasionou alteração na qualidade física do solo, diminuindo a friabilidade dos agregados, e, possibilitando uma maior densidade do comprimento radicular na profundidade 0,0-0,20. O sistema plantio direto (SPD) proporcionou uma maior densidade do comprimento radicular em camadas subsuperficias -0,20-0,40 cm.(AU)

Structural soil quality is desirable for plant growth as well as roots system establishment. Therefore, the objective of this work was to evaluate root distribution, tensile strength and friability of soil aggregates under different management systems in soybean crop. The experimental design was a 2 x 2 x 2 factorial scheme, with factor A: no-tillage (PD) and no-tillage (ES); factor B: with and without application of agricultural plaster and factor C: with and without use of the furrower, arranged in random blocks with three repetitions. At soybean R2 stage, soil collection was performed to evaluate the root system at depths of 0.0-0.05, 0.05-0.10, 0.10-0.20, 0.20-0, 40 and 0.40-0.60 m, with the values of diameter (mm) and length (cm). Soil scarification followed by the use of the furrow stem caused a change in the physical quality of the soil, reducing the friability of the aggregates, and allowing a greater density of root length at depth 0.0-0.20. The no-tillage system (SPD) provided a higher density of root length in subsurface layers -0.20-0.40 cm.(AU)

Distribuição de raízes, resistência tênsil e friabilidade de agregados em solo com diferentes sistemas de manejo / Root distribution, tensil resistance and friability of aggregates in soil with different management systems

A qualidade estrutural do solo é desejável para o crescimento das plantas, assim como estabelecimento do sistema radicular. Diante disso, o objetivo do trabalho foi avaliar a distribuição de raízes, resistência tênsil e a friabilidade de agregados em solo com diferentes sistemas de manejo na cultura da soja. O delineamento experimental foi constituído em esquema fatorial 2 x 2 x 2, sendo fator A: Plantio Direto (PD) e Plantio Direto Escaficado (ESC); fator B: com e sem aplicação de gesso agrícola e fator C: com e sem utilização da haste sulcadora, dispostos em blocos ao acaso com três repetições. No estádio R2 da soja, foi realizada a coleta de solo para avaliação do sistema radicular nas profundidades de 0,0-0,05, 0,05-0,10, 0,10-0,20, 0,20-0,40e 0,40-0,60m, sendo que os valores de diâmetro (mm) e comprimento (cm).A escarificação do solo seguida pela utilização da haste sulcadora, ocasionou alteração na qualidade física do solo, diminuindo a friabilidade dos agregados, e, possibilitando uma maior densidade do comprimento radicular na profundidade 0,0-0,20. O sistema plantio direto (SPD) proporcionou uma maior densidade do comprimento radicular em camadas subsuperficias -0,20-0,40 cm.

Structural soil quality is desirable for plant growth as well as roots system establishment. Therefore, the objective of this work was to evaluate root distribution, tensile strength and friability of soil aggregates under different management systems in soybean crop. The experimental design was a 2 x 2 x 2 factorial scheme, with factor A: no-tillage (PD) and no-tillage (ES); factor B: with and without application of agricultural plaster and factor C: with and without use of the furrower, arranged in random blocks with three repetitions. At soybean R2 stage, soil collection was performed to evaluate the root system at depths of 0.0-0.05, 0.05-0.10, 0.10-0.20, 0.20-0, 40 and 0.40-0.60 m, with the values of diameter (mm) and length (cm). Soil scarification followed by the use of the furrow stem caused a change in the physical quality of the soil, reducing the friability of the aggregates, and allowing a greater density of root length at depth 0.0-0.20. The no-tillage system (SPD) provided a higher density of root length in subsurface layers -0.20-0.40 cm.

Soil physical properties and soil organic carbon content in northeast Brazil: long-term tillage systems effects

Concerns about the negative effects of agriculture on soil physical quality and soil organic carbon (SOC) pools have spurred on the adoption of conservation tillage systems in tropical regions. This study aimed to evaluate the long-term impacts (16th year) of conventional (CT), minimum (MT) and no-tillage (NT) practices and different cover crops (sunn hemp and a bean/millet sequence) on soil physical properties and SOC content of a corn cultivated Ultisol in the northeast of Brazil. Soil bulk density (Bd), soil penetration resistance (SPR), soil aggregation, and total aggregate-associated carbon (C) (4-2 mm) were evaluated. Tillage practices exerted strong control on soil physical properties and total aggregate-C content but were influenced by cover crop species. Minimum tillage presented the lowest Bd, irrespective of cover crop, while NT with bean/millet sequence resulted in the lowest SPR. However, as regards soil aggregation and total aggregate-C, the results indicated that there were no differences between MT and NT, with both systems presenting greater mean weight diameter (MWD) and total aggregate-C content than CT. Total aggregate-C content in the 0.00-0.05 m soil layer in conservation tillage was increased by the adoption of a bean/millet sequence. Increased mechanical disturbance through CT practices was harmful to Bd, soil aggregation and SOC accrual. Overall, more conservative tillage practices and the proper choice of cover crops might yield greater soil quality. Low intensity of soil disturbances due to the adoption of MT favors soil aggregation and the accrual of SOC in weakly structured soils through increases in contact between organic and mineral particles while not causing significant destruction of soil aggregates.(AU)

Effects of green and nitrogen fertilization on the yield and yield components of irrigated winter beans / Adubação verde e nitrogenada sobre os componentes de produção e produtividade do feijoeiro de inverno irrigado

The contribution of plant residues to the soil is an essential requirement for the success of no-tillage systems, especially in areas with a tropical climate where the organic material decomposition rate is high. The type of straw present on the soil surface can influence the culture implanted subsequently, mainly with regard to the availability of nitrogen (N). The objective of this study was to investigate the effect of cultural remains of maize (exclusive or intercropped with cover crops) on the development and productivity of the common bean grown in succession and fertilized with different N doses. The experimental design was a randomized block arranged in a factorial scheme (5 × 4), with four replications. The treatments consisted of combinations of cultural remains of exclusive maize, maize + Crotalaria spectabilis, maize + Cajanus cajan, maize + Canavalia ensiformis, and maize + Urochloa ruziziensis cultivated previously and of four N rates (0, 40, 80, and 120 kg ha-1) applied to bean crops. The plots consisted of seven lines of 7.5 m length with 0.45 m spacing between the lines. The evaluated parameters were: dry matter of the plant cover, dry matter of the aerial part (beans), production components, weight of 100 grains, and grain yield. The intercropping of maize and cover crops promoted an increase in dry matter over the soil, compared to the exclusive maize crop. There was an increase in the dry matter of bean plants with the increase in N rates in the two years of cultivation; regarding productivity, there was an increment only in the first year of cultivation. The maize consortium with cover plants provided adequate soil cover, but did not influence the productivity of beans cultivated in succession in the two years of cultivation.(AU)

O aporte de resíduos vegetais ao solo é um dos requisitos essenciais para o sucesso do plantio direto, principalmente em áreas de clima tropical, cuja taxa de decomposição do material orgânico é elevada. O tipo de palha presente na superfície do solo pode influenciar a cultura implantada na sequência, principalmente ao que diz respeito à disponibilização de nitrogênio (N). Sendo assim, objetivou-se estudar o efeito dos restos culturais de milho (Zea mays L.) exclusivo ou consorciado com plantas de cobertura no desenvolvimento e produtividade do feijoeiro (Phaseolus vulgaris L.) cultivado em sucessão e adubado com doses de N. O delineamento experimental foi o de blocos casualizados disposto em esquema fatorial 5x4, com quatro repetições. Os tratamentos foram constituídos pela combinação do efeito dos restos culturais de milho exclusivo; milho + Crotalaria spectabilis; milho + Cajanus cajan; milho + Canavalia ensiformis; milho + Urochloa ruziziensis, cultivadas anteriormente e, por quatro doses de N aplicadas em cobertura na cultura do feijão (0, 40, 80 e 120 kg ha-1). As parcelas foram constituídas por 7 linhas de 7,5 m de comprimento com espaçamento de 0,45 m. Os parâmetros avaliados foram: matéria seca da cobertura vegetal, matéria seca da parte aérea (feijão), componentes de produção, massa de 100 grãos e produtividade de grãos. O consórcio entre milho e plantas de cobertura promoveu aumento da matéria seca sobre o solo, comparado ao cultivo de milho exclusivo. Houve incremento na matéria seca de plantas de feijão com as doses crescentes de N nos dois anos de cultivo e para a produtividade houve incremento somente no primeiro ano de cultivo. O consórcio do milho com plantas de cobertura proporcionou adequada cobertura do solo, porém não influenciou a produtividade do feijoeiro cultivado em sucessão nos dois anos de cultivo.(AU)

Soil physical properties and soil organic carbon content in northeast Brazil: long-term tillage systems effects

Concerns about the negative effects of agriculture on soil physical quality and soil organic carbon (SOC) pools have spurred on the adoption of conservation tillage systems in tropical regions. This study aimed to evaluate the long-term impacts (16th year) of conventional (CT), minimum (MT) and no-tillage (NT) practices and different cover crops (sunn hemp and a bean/millet sequence) on soil physical properties and SOC content of a corn cultivated Ultisol in the northeast of Brazil. Soil bulk density (Bd), soil penetration resistance (SPR), soil aggregation, and total aggregate-associated carbon (C) (4-2 mm) were evaluated. Tillage practices exerted strong control on soil physical properties and total aggregate-C content but were influenced by cover crop species. Minimum tillage presented the lowest Bd, irrespective of cover crop, while NT with bean/millet sequence resulted in the lowest SPR. However, as regards soil aggregation and total aggregate-C, the results indicated that there were no differences between MT and NT, with both systems presenting greater mean weight diameter (MWD) and total aggregate-C content than CT. Total aggregate-C content in the 0.00-0.05 m soil layer in conservation tillage was increased by the adoption of a bean/millet sequence. Increased mechanical disturbance through CT practices was harmful to Bd, soil aggregation and SOC accrual. Overall, more conservative tillage practices and the proper choice of cover crops might yield greater soil quality. Low intensity of soil disturbances due to the adoption of MT favors soil aggregation and the accrual of SOC in weakly structured soils through increases in contact between organic and mineral particles while not causing significant destruction of soil aggregates.

Carbon indices to assess quality of management systems in a Subtropical Acrisol

Management systems to improve soil quality are essential for agricultural and environmental sustainability. We assessed the quality of soil management systems applied to a subtropical Acrisol in terms of the carbon management index (CMI), the stratification ratio for total organic carbon (SR-TOC) and light fraction of organic matter (SR-LF). In addition, we examined their relationship to chemical, physical and biological soil quality indicators, as well as to maize yield. The study was conducted on a long-term experiment (18 years) in southern Brazil involving two different systems [no tillage (NT) and conventional tillage (CT)], two cropping systems [black oat/maize (O/M) and black oat + vetch/maize + cowpea (OV/MC)] and two nitrogen fertilizer rates for maize (0 and 180 kg ha–1). Based on the three indices, the best managements for soil quality comprised NT (50-212 % better than CT), legume cover crops (10-47 % better than O/M) and N fertilization (8-33 % better than no fertilizer). All three indices proved accurate to assess the impact of soil management systems, especially SR-LF, which showed increased sensitivity and close relationships with chemical, physical and biological soil quality indicators. On the other hand, a poor relationship was observed between soil C indices and maize yield, which was improved only by legume cover crops and N fertilization. The results showed that the association of no-till system to an abundant supply of crop residues is key to ensure high soil quality and crop yields in humid subtropical regions.(AU)

Carbon indices to assess quality of management systems in a Subtropical Acrisol

Management systems to improve soil quality are essential for agricultural and environmental sustainability. We assessed the quality of soil management systems applied to a subtropical Acrisol in terms of the carbon management index (CMI), the stratification ratio for total organic carbon (SR-TOC) and light fraction of organic matter (SR-LF). In addition, we examined their relationship to chemical, physical and biological soil quality indicators, as well as to maize yield. The study was conducted on a long-term experiment (18 years) in southern Brazil involving two different systems [no tillage (NT) and conventional tillage (CT)], two cropping systems [black oat/maize (O/M) and black oat + vetch/maize + cowpea (OV/MC)] and two nitrogen fertilizer rates for maize (0 and 180 kg ha–1). Based on the three indices, the best managements for soil quality comprised NT (50-212 % better than CT), legume cover crops (10-47 % better than O/M) and N fertilization (8-33 % better than no fertilizer). All three indices proved accurate to assess the impact of soil management systems, especially SR-LF, which showed increased sensitivity and close relationships with chemical, physical and biological soil quality indicators. On the other hand, a poor relationship was observed between soil C indices and maize yield, which was improved only by legume cover crops and N fertilization. The results showed that the association of no-till system to an abundant supply of crop residues is key to ensure high soil quality and crop yields in humid subtropical regions.

Ammonia volatilization in response to coated and conventional urea in maize crop field / Volatilização de amônia utilizando ureia convencional e revestida na cultura do milho

The properly measurement of gas emissions and nutrient availability to crops using technologies such as polymer-coated urea are required to monitored the possible nitrogen (N) fertilizer pollution in the environment. This study aimed to evaluate N loss through ammonia volatilization from polymer-coated and conventional urea in maize field trials under two different environments. The study was carried out in Chapadão do Sul and Selvíria State of Mato Grosso do Sul evaluating the first and second harvest of maize plants. Nitrogen fertilizers were applied as polymer-coated, conventional urea and control plots were used as reference to evaluate N loss through volatilization (3, 6, 9, 12, and 15 days after fertilizer application). The peak of ammonia volatilization was observed during the first three days after fertilizer application corresponding up to 44% of total N supplied. Polymer-coated urea had promising results showing less ammonia volatilization during the first crop. However, the same result was not observed for second crop.

A necessidade de mensurar adequadamente a emissão de gases e também o fornecimento de nutrientes às culturas por tecnologias como o revestimento da ureia com polímeros são necessários para monitar a possível poluição de fertilizantes nitrogenados no ambiente. Assim, o objetivo desse trabalho foi determinar as perdas de nitrogênio (N) por volatilização pela ureia convencional e ureia revestida compolímero, em duas épocas de cultivo do milho (Zea mays L.), em duas regiões do cerrado brasileiro. Os trabalhos foram desenvolvidos em Chapadão do Sul e Selvíria, Mato Grosso do Sul - Brasil, na cultura do milho "primeira safra" e "segunda safra", respectivamente. Os tratamentos foram constituídos pela ureia e ureia revestida por polímero aplicada em cobertura além de um tratamento controle (sem N) em função de épocas de monitoramento das perdas de N por volatilização (3, 6, 9, 12 e 15 dias após a adubação) com 5 repetições. Foi mensurado as perdas de N por volatilização nas respectivas épocas e o total acumulado no período. O pico de volatilização ocorreu durante os três primeiros dias, atingindo patamares de até 44% do total de N fornecido. O revestimento da ureia com polímeros apresentou resultados promissores, diminuindo as perdas de N-NH3 por volatilização no milho "primeira safra". Todavia, os resultados obtidos no milho "segunda safra" não permitem generalizar tais benefícios.

Agro-ecological options for fall armyworm (Spodoptera frugiperda JE Smith) management: Providing low-cost, smallholder friendly solutions to an invasive pest.

Fall armyworm (FAW), a voracious agricultural pest native to North and South America, was first detected on the African continent in 2016 and has subsequently spread throughout the continent and across Asia. It has been predicted that FAW could cause up to $US13 billion per annum in crop losses throughout sub-Saharan Africa, thereby threatening the livelihoods of millions of poor farmers. In their haste to respond to FAW governments may promote indiscriminate use of chemical pesticides which, aside from human health and environmental risks, could undermine smallholder pest management strategies that depend to a large degree on natural enemies. Agro-ecological approaches offer culturally appropriate low-cost pest control strategies that can be readily integrated into existing efforts to improve smallholder incomes and resilience through sustainable intensification. Such approaches should therefore be promoted as a core component of integrated pest management (IPM) programmes for FAW in combination with crop breeding for pest resistance, classical biological control and selective use of safe pesticides. Nonetheless, the suitability of agro-ecological measures for reducing FAW densities and impact need to be carefully assessed across varied environmental and socio-economic conditions before they can be proposed for wide-scale implementation. To support this process, we review evidence for the efficacy of potential agro-ecological measures for controlling FAW and other pests, consider the associated risks, and draw attention to critical knowledge gaps. The evidence indicates that several measures can be adopted immediately. These include (i) sustainable soil fertility management, especially measures that maintain or restore soil organic carbon; (ii) intercropping with appropriately selected companion plants; and (iii) diversifying the farm environment through management of (semi)natural habitats at multiple spatial scales. Nevertheless, we recommend embedding trials into upscaling programmes so that the costs and benefits of these interventions may be determined across the diverse biophysical and socio-economic contexts that are found in the invaded range.

Profitability of no-till grain production systems / Rentabilidade de sistemas de produção de grãos sob plantio direto

In general, the technical and agronomic benefits of no-till farming are widely known and well documented in the literature. However, studies focusing on the economics of no-tillage are scarce. In this context, the objective of this study is to determine whether no-till grain production systems that follow the principles of conservation agriculture are economically profitable by analyzing gross margins per hectare per year over six harvests for the agricultural years 1998/1999 to 2003/2004. In addition, a possible link between profitability and different no-till methods in terms of degree of soil turnover, crop rotation, and whether machinery used in agricultural operations is owned or rented is investigated. For this purpose, the multi-case analytical method was applied to thirteen grain producing family farms in Northern Paraná state, Brazil. Based on the results, two ranges of agricultural production variable costs and gross margins were identified. Higher gross margins were associated with longer use of the no-till system, ownership of machinery and equipment, specialization in grains, rotation of the commercial crops used, and higher variable costs. Lower gross margins were associated with outsourcing of sowing, small-scale cropping, and lack of crop rotation. It is concluded that family mechanized no-till systems of grain production in north Paraná are profitable.(AU)

Em geral, os benefícios técnico-agronômicos do plantio direto são amplamente conhecidos e encontram-se bem documentados na literatura, entretanto, estudos voltados aos aspectos econômicos do plantio direto são escassos. Nesse contexto, o objetivo deste estudo foi avaliar a rentabilidade de lavouras de grãos, sob plantio direto, por meio da análise das margens brutas por hectare ao ano, ao longo de seis safras, considerando os anos agrícolas de 1998/1999 a 2003/2004. Além disso, foi averiguada se há uma relação entre a rentabilidade e os diferentes tipos de plantio direto, no que diz respeito ao grau de revolvimento do solo, à realização de rotação de culturas e se o maquinário para a realização das operações agrícolas era próprio ou alugado. Para tanto, utilizou-se a metodologia de análise multicaso, considerando treze estabelecimentos agrícolas familiares, produtores de grãos, do Norte do Paraná, Brasil. Com base nos resultados foram identificados duas faixas de custos variáveis e de margens brutas da produção agrícola. Maiores margens brutas estiveram associadas ao maior tempo de utilização do sistema plantio direto, à posse de maquinário e equipamentos próprios, à especialização em grãos, à rotação de culturas comerciais utilizadas e aos maiores custos variáveis. Menores margens brutas estiveram associadas ao uso de terceirização na semeadura, à pequena escala das lavouras e...(AU)

Profitability of no-till grain production systems / Rentabilidade de sistemas de produção de grãos sob plantio direto

In general, the technical and agronomic benefits of no-till farming are widely known and well documented in the literature. However, studies focusing on the economics of no-tillage are scarce. In this context, the objective of this study is to determine whether no-till grain production systems that follow the principles of conservation agriculture are economically profitable by analyzing gross margins per hectare per year over six harvests for the agricultural years 1998/1999 to 2003/2004. In addition, a possible link between profitability and different no-till methods in terms of degree of soil turnover, crop rotation, and whether machinery used in agricultural operations is owned or rented is investigated. For this purpose, the multi-case analytical method was applied to thirteen grain producing family farms in Northern Paraná state, Brazil. Based on the results, two ranges of agricultural production variable costs and gross margins were identified. Higher gross margins were associated with longer use of the no-till system, ownership of machinery and equipment, specialization in grains, rotation of the commercial crops used, and higher variable costs. Lower gross margins were associated with outsourcing of sowing, small-scale cropping, and lack of crop rotation. It is concluded that family mechanized no-till systems of grain production in north Paraná are profitable.

Em geral, os benefícios técnico-agronômicos do plantio direto são amplamente conhecidos e encontram-se bem documentados na literatura, entretanto, estudos voltados aos aspectos econômicos do plantio direto são escassos. Nesse contexto, o objetivo deste estudo foi avaliar a rentabilidade de lavouras de grãos, sob plantio direto, por meio da análise das margens brutas por hectare ao ano, ao longo de seis safras, considerando os anos agrícolas de 1998/1999 a 2003/2004. Além disso, foi averiguada se há uma relação entre a rentabilidade e os diferentes tipos de plantio direto, no que diz respeito ao grau de revolvimento do solo, à realização de rotação de culturas e se o maquinário para a realização das operações agrícolas era próprio ou alugado. Para tanto, utilizou-se a metodologia de análise multicaso, considerando treze estabelecimentos agrícolas familiares, produtores de grãos, do Norte do Paraná, Brasil. Com base nos resultados foram identificados duas faixas de custos variáveis e de margens brutas da produção agrícola. Maiores margens brutas estiveram associadas ao maior tempo de utilização do sistema plantio direto, à posse de maquinário e equipamentos próprios, à especialização em grãos, à rotação de culturas comerciais utilizadas e aos maiores custos variáveis. Menores margens brutas estiveram associadas ao uso de terceirização na semeadura, à pequena escala das lavouras e...