Agostinho Dirceu Didonet

Sistemas de preparo do solo e culturas de cobertura na produção orgânica de feijão e milho: I - atributos físicos do solo

Ha necessidade de se avaliar a contribuicao de plantas de cobertura e do seu manejo na manutencao ou melhoria da qualidade fisica do solo em areas sob producao orgânica. Este trabalho objetivou determinar a influencia das plantas de cobertura crotalaria (Crotalaria juncea), guandu (Cajanus cajan (L.) Millsp), mucuna-preta (Mucuna aterrima), sorgo-vassoura (Sorgum technicum) e pousio nos atributos fisicos de solo cultivado com feijao e milho orgânicos, sob semeadura direta (SD) e preparo convencional (PC). O trabalho foi conduzido em Santo Antonio de Goias-GO, em Latossolo Vermelho distrofico, no delineamento de blocos ao acaso, com quatro repeticoes. Em novembro de 2003 foram instalados quatro experimentos, dois em SD e dois em PC, sendo um com feijao e outro com milho em cada sistema. Amostragens do solo das parcelas e de uma mata proxima aos experimentos foram realizadas em novembro de 2007, nas camadas de 0,00-0,10 e 0,10-0,20 m, para determinacao do teor de materia orgânica (MO) e de atributos fisicos do solo. O uso desse solo para a producao agricola, independentemente do sistema de preparo, resultou em reducao no teor de MO e em modificacoes nos seus atributos fisicos, aumentando sua densidade (Ds) e resistencia a penetracao (RP) e reduzindo a macroporosidade (Mp), porosidade total (Pt) e diâmetro medio ponderado dos agregados (DMP). Entretanto, a Ds e a Mp nao atingiram os valores criticos preconizados na literatura como limitantes ao desenvolvimento das culturas. Os sistemas de preparo do solo divergiram quanto ao DMP e a RP. Os atributos fisicos do solo foram alterados favoravelmente pela MO. O indice S correlacionou-se com os atributos fisicos do solo e com o teor de MO, mostrando-se adequado como indicador da qualidade fisica do solo.

Soil tillage systems and cover crops in organic production of common bean and corn: II - soil biological properties

The influence of cover crops and their management on the maintenance or improvement of soil physical quality in areas under organic production should be investigated. This study aimed to determine the influence of the cover crops sunn hemp (Crotalaria juncea), pigeon pea (Cajanus cajan (L.) Millsp), velvet bean (Mucuna aterrima), sorghum (Sorgum technicum), and fallow on physical properties of soil under organic cultivation of common bean and corn, in no-tillage (NT) and conventional tillage (CT) systems. The study was conducted in Santo Antonio de Goias-GO, on an Oxisol, in a randomized block design, with four replications. In November 2003 four experiments were installed, two of them under NT and the other two in CT. In each management system, one experiment was carried out with common bean and another with corn. Samples were taken from the layers 0.00-0.10 and 0.10-0.20 m in November 2007, from the plots and from a neighboring native forest, to determine soil organic matter (SOM) and physical properties. The use of this soil for agricultural production, regardless of the tillage system, reduced the SOM content and affected the physical properties, increased bulk density (BD) and soil penetration resistance (PR) and decreased macroporosity (Mp), soil porosity (SP), and the weighted mean diameter of aggregates (WMDA). However, BD and Mp did not reach the critical values indicated in the literature as limiting for crop growth. The soil tillage systems diverged in relation to WMDA and PR. The soil physical properties were favorably affected by SOM. The S index was correlated to the soil physical properties and to SOM and seems to be an adequate indicator of soil physical quality.

Fifty years of wheat breeding in Southern Brazil: yield improvement and associated changes

The objective of this study was to assess the impact of genetic breeding on grain yield, and to identify the physiological traits associated to the increment in yield and their related growth processes, for wheat cultivars grown in Southern Brazil, in the past five decades. Seven wheat cultivars released between 1940 and 1992, were compared for physiological aspects associated with grain yield. Grain yield, biological yield, biomass partitioning, harvest index and grain yield components were also determined. The number of grains per square meter was more affected by plant breeding and was better correlated with grain yield (r = 0.94, p<0.01) than with grain weight (r = -0.39 ns ). The higher number of grains per square meter was better correlated with the number of grains per spike in the modern cultivars than in the older ones. The genetic gain in grain yield was 44.9 kg ha -1 per year, reflecting important efforts of the breeding programs carried out in Southern Brazil. Grain yield changes, during the period of study, were better associated with biomass production (r = 0.78, p<0.01) than with harvest index (r = 0.65, p<0.01).

Atributos físicos, químicos e biológicos de solo sob produção orgânica impactados por sistemas de cultivo

Este trabalho objetivou determinar quais atributos de um Latossolo Vermelho de Cerrado sob producao orgânica sao mais impactados por sistemas de cultivo compostos por feijao e milho, semeadura direta (SD) e preparo convencional (PC) do solo e plantas de cobertura. Aplicaram-se tecnicas de analise multivariada nos dados de quatro experimentos, dois em SD e dois em PC, um com feijao e outro com milho em cada preparo, instalados desde novembro de 2003, em Santo Antonio de Goias, GO, no delineamento de blocos ao acaso, com quatro repeticoes. Em setembro de 2003 foram retiradas amostras de solo na camada de 0 - 0,10 m para analise quimica inicial (referencia quimica). Em novembro de 2007 foi feita nova amostragem nas parcelas e em uma mata proxima (referencia fisica e biologica) para determinacao dos atributos fisicos (AF), quimicos (AQ) e biologicos (AB) do solo. Os sistemas de cultivo provocaram alteracoes nos AF e AB, quando comparados com a mata, e nos AQ, quando comparados com a condicao inicial, sendo os AF mais sensiveis em detectar mudancas na qualidade do solo sob cultivo. Os quocientes metabolico e microbiano foram os mais afetados negativamente pelo PC quando comparados com a SD. Os AQ foram mais sensiveis em discriminar a cultura do feijao da do milho.

Realocação de nitrogênio e de biomassa para os grãos, em trigo submetido a inoculação de Azospirillum

The effect of inoculating wheat (Triticum aestivum L.) seeds, cultivar Embrapa 16, with powder peat inoculant containing Azospirillum bacteria on yield and remobilization of nitrogen and biomass was studied under field conditions. The strain of Azospirillum brasilense 245 and the isolate 10 of Azospirillum lipoferum were used as inoculants. Different rates of nitrogen were applied at varying stages of plant growth for each inoculated and non-inoculated treatment, distributed in blocks at random with split plots. The accumulation of dry matter and total nitrogen in plant parts was evaluated at anthesis and physiological maturity stages. Harvest index for biomass and N, main yield components, and total N content in the seeds, in addition to yield, were also evaluated at harvest. The preliminary results showed that, even without inoculation effect on yield, there was a better allocation of nitrogen and biomass to the seeds, resulting in heavier seeds, with a lower amount of nitrogen remaining in the straw at physiological maturity. Such effects resulted from a lower number of spikes m-2, probably due to the death of tillers, determining a greater availability of N and biomass to the remaining spikes and seeds.Estudou-se, em condicoes de campo, o efeito de inoculante turfoso em po contendo bacterias do genero Azospirillum no rendimento de graos e na remobilizacao de N e de biomassa para os graos de trigo (Triticum aestivum L.), cultivar Embrapa 16. Usaram-se como inoculantes, a estirpe de Azospirillum brasilense 245 e o isolado 10 de Azospirillum lipoferum. Em cada tratamento de inoculacao, e tambem sem inoculacao, aplicaram-se diferentes doses de N em diferentes estadios de desenvolvimento das plantas, distribuidos em blocos ao acaso com parcelas subdivididas. Na antese e na maturacao fisiologica, avaliaram-se o acumulo de massa seca e N total nas diferentes partes da planta. Na colheita, alem do rendimento de graos, avaliaram-se tambem o indice de colheita para biomassa e para N, os principais componentes do rendimento e o teor de N total de graos. Os resultados ainda preliminares evidenciaram que, mesmo nao havendo efeito da inoculacao no rendimento de graos, houve um melhor alocamento de N e de biomassa para os graos, resultando em maior massa de mil graos e em menor quantidade de N restante na palha das plantas na maturacao fisiologica. Esses efeitos resultaram de um menor numero de espigas m-2, provavelmente devido a morte de afilhos, fator que determinou maior disponibilidade de N e de biomassa as espigas e graos restantes.

Eficiência de uso da radiação solar na produtividade do trigo decorrente da adubação nitrogenada

An experiment was carried out at Embrapa Rice and Beans, Santo Antonio de Goias, Goias State, Brazil, under no-tillage in the soybean mulch to evaluate the effects of nitrogen doses on the solar radiation use efficiency, leaf area index in the anthesis, biomass in the anthesis, in the physiological maturation and grain yield of two wheat cultivars. A randomized block design in subdivided plots, with four replications was used. In the plots five nitrogen topdressing doses, 0, 50, 100, 150, and 200 kg ha-1 were established and in the subplots, the cultivars Embrapa 22 and Embrapa 42. The cultivars differed only in relation to biomass in anthesis. The analyzed variables showed a quadratic response to nitrogen doses. Wheat grain yield response to nitrogen was due to the effect of this nutrient in the leaf area index, that affected solar radiation use efficiency and biomass, which showed a positive correlation with grain yield. Under low nitrogen availability, grain yield showed higher correlation to biomass accumulated in the anthesis than to that accumulated in the physiological maturation.

Chemical properties of an oxisol under organic management as influenced by application of sugarcane bagasse ash

There are large areas of Oxisols in South America, including Brazil, with low fertility and acidity. To improve crop yields on these Oxisols, liming and fertilization is an essential practice. However, besides the high cost of fertilizers, chemical fertilizers cannot be used in organic production systems, except insoluble sources. Ash is one of the alternative source of supplying macro and micronutrients. A field experiment was conducted, in a completely randomized block design in a factorial arrangement (three sources of ash x four rates) resulting on 12 treatments, to evaluate the effect of source and rate of ash application on soil chemical properties. The treatments consisted of three sources (bagasse, bagasse+PJ07-A and bagasse+PJ07-RA) of sugarcane ash applied in four rates as 0; 5; 15 and 30 Mg ha -1 . Results showed that the use of ash significantly improved soil chemical properties such as pH, P, K, Mg, base saturation, K and Mg saturation and significantly reduced soil acidity (H+Al). Depending on the ash source or rate, some of the soil chemical properties were affected, however, the effect of ash source was not so pronounced as compared with ash rate. Ashes application resulted on a soil nutritional condiction enough to guarantee the growth and yield of most annual crops. Ash sources were equally effective in reducing acidity and improving soil fertility under this study condition, while increasing ash rate provides decrease in H+Al content and increase in pH, Mg, P and K.

Atributos químicos de solo sob produção orgânica influenciados pelo preparo e por plantas de cobertura

This study aimed to determine the influence of the cover crops sunhemp (Crotalariajuncea), pigeon pea (Cajanus cajan (L.) Millsp), velvet bean (Mucuna aterrima), sorghum (Sorgum technicum), and fallow on chemical attributes of soil cultivated with organic common bean and corn, under no-tillage (NT) and conventional tillage (CT) systems. The work was conducted in Santo Antonio de Goias-GO, in Oxisol, in a randomized block design, with four replications. In November 2003 four experiments were installed, two of them under NT and the other two in CT. In each soil management system, an experiment was carried out with common bean crop and another with corn. Samples were taken from soil layers of 0-0.10 and 0.10-0.20 m in September 2003 and in November 2007. The soil pH and the contents of P, K+, Ca2+, Mg2+, Cu2+, Zn2+, Fe3+, Mn2+, H+ + Al3+, and soil organic matter were analyzed, and cation exchange capacity and base saturation were calculated. After four years, cover crops did not differ in their effects on soil chemical attributes, however, they increased the content of organic matter in relation to initial condition, under NT or in CT. In general, the nutrient recycling by cover crops was not sufficient to maintain the P, K+, Fe3+ and Mn2+ contents in the soil.

Produtividade do feijoeiro comum influenciada por plantas de cobertura e sistemas de manejo do solo

A field experiment was carried out under no-tillage system (NT) and conventional tillage (CT) to assess the dry mass production, N accumulation and the decomposition rate of crotalaria (Crotalaria juncea) and sorghum (Sorghum bicolor L.), as well as, their effects on the grain yield of common bean (Phaseolus vulgaris L.). Results showed that soil management had no effect on the dry mass production of cover crop, however, the sorghum produced 60% more dry mass as compared with crotalaria. The largest N accumulation was observed under NT, which showed 45% more N than CT, however, no statistical difference between cover crops was observed. The straw rate decomposition under NT was 50% lower than under CT and, until 28 days, the decomposition of crotalaria under CT was faster than sorghum. The common bean grain yield was 40% higher under NT as compared with CT and it showed high correlation with N amount accumulated by the cover crops. Under Cerrado condition of Goias state, NT promotes greater N accumulation and lower decomposition rate of the cover crops, leading to greater grain yield of common bean as compared with CT.

Soluble tissue sugar content and leaf blast severity in response to the application of calcinated serpentinite as a silicon source in irrigated rice

ABSTRACT A field experiment conducted with the irrigated rice cultivar BRSFormoso, to assess the efficiency of calcinated serpentinite as a siliconsource on grain yield was utilized to study its effect on leaf blastseverity and tissue sugar levels. The treatments consisted of fiverates of calcinated serpentinite (0, 2, 4, 6, 8 Mg.ha -1 ) incorporatedinto the soil prior to planting. The leaf blast severity was reduced at Prabhu, A.S.; Santos, A.B. dos; Didonet, A.D. Soluble tissue sugar content and leaf blast severity in response to the application of calcinatedserpentinite as a silicon source in irrigated rice. Summa Phytopathologica , v.33, n.4, p.402-404, 2007. RESUMO Um experimento de campo, para avaliar a eficiencia de serpentinitocalcinado como fonte de silicio na produtividade da cultura de arrozirrigado, cultivar BRS Formoso, foi utilizado para estudar seu efeitosobre a brusone nas folhas e niveis de acucares nos tecidos. Ostratamentos consistiram de cinco doses de serpentinito calcinado (0,2, 4, 6, 8 Mg.ha