Edmilson José Ambrosano

Utilization of nitrogen from green manure and mineral fertilizer by sugarcane

Given their potential for biological nitrogen fixation, legumes used as green manure are an alternative source of nitrogen to crops, and can supplement or even replace mineral nitrogen fertilization. The utilization of nitrogen by sugarcane (Saccharum spp.) fertilized with sunn hemp (Crotalaria juncea L.) and ammonium sulphate (AS) was evaluated using the 15N tracer technique. Amounts of 195.8 kg and 70 kg N per hectare, respectively, of sunn hemp and AS were added in the following treatments: without green manure and without AS; without green manure, with AS -15N; with green manure-15N and with AS; with green manure-15N, without AS; with green manure and with AS-15N. Four samples from the leaves +3 were collected and 2 m of the sugar cane row were harvested to estimate crop yield. The results for N contents (g kg-1), isotopic abundance of N (atoms % 15N) in leaf +3 samples, and sugarcane productivity were used to calculate cumulative N, nitrogen in the plant derived from the fertilizer-Ndff (% and kg ha-1), as well as percent recovery of fertilizer N (R%). Sugarcane was analysed and pol and total recovered sugar calculated. The highest Ndff percentages were observed eight months after sugarcane planting for treatments containing green manure without mineral N, and green manure with mineral N, at 15.3 and 18.4%, respectively. The best nitrogen recovery was observed during harvest, 18 months after planting; the treatment containing mineral fertilizer showed 34.4% recovery, while the sum between mineral N plus green manure N showed 40.0%. Treatments containing green manure plus mineral N changed soil attributes, by increasing Ca and Mg contents, sum of bases, pH, and base saturation, and decreasing potential acidity. In the plant, those treatments increased Ca and K contents.

EFEITO DO NITROGÊNIO NO CULTIVO DE FEIJÃO IRRIGADO NO INVERNO

An experiment was conducted at three localities, namely, Ribeirao Preto (Latosolic B Terra Roxa), Votuporanga (Dark red latossol sandy phase) and Pindorama (Podzolic Lins-Marilia), in the State of Sao Paulo, Brazil. The objetive was to evaluate the response of nitrogen on irrigated dry beans during a two year period at Ribeirao Preto and Votuporanga (1990, 1991) and in Pindorama (1992, 1993). The experimental design was a complete randomized blocks design with five replications. The results showed that the yield of irrigated dry beans in the winter can be increased adding nitrogen. The sprint application is recommendable for the low fertility soil (Pindorama). The combination of N applied to the soil and on the leaves was more effective than that only on the leaves. The single dose applied at the 25th day after germination was more effective than the one aplied at the sowing date.

Crop rotation biomass and arbuscular mycorrhizal fungi effects on sugarcane yield

A cana-de-acucar (Saccharum spp.) vem sendo cultivada no Brasil para producao de acucar e agroenergia. Em seu sistema de producao, apos um ciclo de 4 a 8 anos, e possivel a rotacao com plantas de cobertura, antes do seu replantio, para melhoria do solo e geracao de renda. Estudou-se a caracterizacao e produtividade de biomassa de leguminosas (como adubos-verdes) e girassol (Helianthus annuus L.), a ocorrencia natural de micorrizas, o teor de acucar e a produtividade em colmos da cana-de-acucar IAC 87-3396 e a viabilidade economica desse sistema com cultivo apos as opcoes de rotacao, com quantificacao da produtividade durante tres cortes consecutivos. O amendoim (Arachis hypogaea L.) cv. IAC-Caiapo, girassol cv. IAC-Uruguai e mucuna-preta (Mucuna aterrimum Piper and Tracy) foram as culturas que apresentaram maior percentagem de colonizacao por fungos micorrizicos. O girassol foi a planta de cobertura que mais extraiu nutrientes do solo, seguido por amendoim (Arachis hipogaea L.) cv. IAC-Tatu e feijao-mungo (Vigna radiata L. Wilczek). A colonizacao por fungos micorrizicos mostrou correlacao positiva com a altura de plantas de cana no primeiro corte (p = 0,01 e R = 0,52), mas nao se correlacionou com a produtividade de colmos ou acucar. No primeiro corte, o girassol foi a cultura de rotacao que ocasionou o maior aumento de produtividade, da ordem de 46% em colmos e de 50% na quantidade de acucar, em comparacao com a testemunha. Com excecao dos amendoins, todas as culturas em rotacao aumentaram a renda liquida do sistema na media de tres cortes de cana-de-acucar.

15N-labeled nitrogen from green manure and ammonium sulfate utilization by the sugarcane ratoon

Leguminosas, como adubo verde, sao fontes alternativas de nitrogenio para as culturas e podem complementar ou mesmo substituir a adubacao mineral nitrogenada, devido ao seu potencial de fixacao biologica de nitrogenio (FBN). A utilizacao do nitrogenio pela cana-de-acucar (Saccharum spp.) fertilizada com crotalaria (Crotalaria juncea L.) e sulfato de amonio (SA) foi avaliada utilizando a tecnica de tracador 15N. As quantidades equivalentes a 196 e 70 kg de N por hectare foram adicionados como adubo verde crotalaria juncea (CJ) e como o sulfato de amonio (SA), respectivamente, nos seguintes tratamentos: (i) controle; (ii) SA15N; (iii) CJ15N + SA; (iv) CJ15N; e (v) SA15N + CJ. A cana-de-acucar foi cultivada por cinco anos e colhida tres vezes. A recuperacao do 15N foi avaliada nas duas primeiras colheitas. Na soma das tres safras, os maiores rendimentos de colmos foram obtidos com uma combinacao de adubos verdes e fertilizantes N inorgânicos, mas, no segundo corte rendimentos superiores foram observados nos tratamentos com CJ em comparacao com os observados com SA. A recuperacao de N nas primeiras duas safras consecutivas representou 19 a 21% do N aplicado como adubo verde e 46 a 49% do N aplicado como SA. As quantidades de N inorgânico derivado das fontes marcadas, presentes na camada 0-0,4 m do solo na primeira safra apos a aplicacao do N foram inferiores a 1 kg ha-1.

Nitrogen-15 labeling of Crotalaria juncea green manure

A grande maioria dos estudos com a utilizacao de material vegetal marcado com o isotopo 15N nao apresentam detalhes tao importantes sobre como foram obtidos esses materiais. Em se tratando de marcacao de leguminosas as dificuldades em se obter material marcado com 15N sao ainda maiores pelo fato de serem plantas fixadoras de nitrogenio. Isso posto foi estabelecida uma tecnica de marcacao de leguminosas com nitrogenio (15N), com o objetivo de obter material vegetal marcado isotopicamente para estudos de dinâmica do nitrogenio. Cultivou-se a leguminosa crotalaria juncea (Crotalaria juncea L.), em Argissolo Vermelho Amarelo distrofico, em campo. Ao se aplicarem via foliar 58,32 gramas de ureia em oito canteiros experimentais, (ureia com 70,57 ± 0,04% de atomos de 15N) parceladas em tres vezes, obteve-se material vegetal marcado seco que continha 2,412 % em atomos de 15N em uma massa seca equivalente a 9 Mg ha-1. Essa marcacao permite o uso dessa massa vegetal em estudos de dinâmica de nitrogenio.

Nitrogen supply to corn from sunn hemp and velvet bean green manures

Due to their nitrogen fixation potential, legumes represent an alternative for supplying nutrients, substituting or complementing mineral fertilization in cropping systems involving green manuring. The objective of this study was to evaluate the N balance in a soil-plant system involving green manures [sunn hemp (Crotalaria juncea L.) and velvet bean (Mucuna aterrima Piper & Tracy)], both labeled with 15N. They were incorporated into two soils of contrasting textural classes: a clayey Eutrudox and a sandy-clayey Paleudalf, both cultivated with corn. The research was carried out in a greenhouse, using pots containing 6 kg of air dried soil, to which the equivalent to 13 Mg ha-1 dry matter of above-ground mass plus 2.7 or 2.2 Mg ha-1 of velvet bean and sunn hemp roots were incorporated, respectively, with 15N labeling of either shoots or roots. One hundred days after emergence of the corn, the velvet bean residues provided higher accumulation of N in the soil, higher absorption by corn plants and accumulation in the shoot. The green manure decomposition was more intense in the medium-textured Paleudalf. The highest nitrogen losses were also observed in this soil.

Desempenho de cultivares de tomateiro em sistema orgânico sob cultivo protegido

Organic agriculture in Brazil has been increasing about 30% per year over the last few years, since consumers are seeking for healthier foods, i.e. nutritious and free of pesticide residues. Among organically grown vegetable crops, tomato is an attractive economic opportunity for growers. However, the lack of information about management practices and adapted cultivars to organic production systems under protected cultivation are pointed out as important constraints that prevents this activity to expand. This work aimed at evaluating the performance of indeterminate tomato cultivars in organic management systems in unheated plastic greenhouse. In both experiments tomato plants were staked. Plant spacing was 1.5 m between rows and 0.35 m between plants. They were planted in double line and spaced 0.8 m between lines and 0.6 m between plants (about 20,000 plants ha-1). The experiment was set up in a randomized complete block design, with four replications and eight treatments (cultivars: Avalon, Colibri, HTX-5415, HTX-8027, Sahel, San Marzano, San Vito, and Jane). Sahel hybrid exhibited an outstanding performance for marketable yield under organic cultivation. Tomato pinworm (Tuta absoluta) was a serious limiting pest for organically grown tomatoes, responding for 17% of damage in the fruits harvested from the evaluated cultivars.

Utilização de nitrogênio pelo trigo cultivado em solo fertilizado com adubo verde(Crotalaria juncea) e/ou uréia

The aim of this work was to evaluate the use of green manure nitrogen (Crotalaria juncea L.)-15N and urea-15N, in conjugated and separate fertilization. The experiment was carried out in pots with 5kg of a Rhodic Hapludox (sample collected in 0-20cm depth), using wheat (Triticum aestivum L.), cv. IAC-24. The completely randomized design was used with 5 treatments and 4 replicates: T1 - urea-15N (45mg kg-1 of N-urea); T2 - Crotalaria juncea-15N (100mg kg-1 of N-crotalaria); T3 - Crotalaria juncea-14N (100mg kg-1 of N-crotalaria) and urea-15N (45mg.kg-1 of N-urea); T4 - urea-14N (45mg.kg-1 of N-urea) and Crotalaria juncea-15N (100mg.kg-1 of N-crotalaria); T5 - treatment control (without source with N). The harvest of plants was realized 50 days after emergency (DAE), at flowering stage, separating the shoot of the root, being also sampled the soil of each pot. The parameter evaluated were the dry weight, height of plants, content of N and 15N abundance, being calculated the recovery of nitrogen from the sources. The N-urea recovery in wheat was larger, compared to N-crotalaria that stayed immobilized in the soil. In the soil-plant system, the N-crotalaria recovery was higher then N-urea. The soil fertilization with urea conjugated with crotalaria or applied separately resulted in larger dry weight and content of N in wheat. The use of Crotalaria juncea as green manure provided conservation of nitrogen, promoting larger recovery of the nutrient in the soil-plant system.

TÉCNICA PARA MARCAÇÃO DOS ADUBOS VERDES CROTALÁRIA JÚNCEA E MUCUNA-PRETA COM 15N PARA ESTUDOS DE DINÂMICA DO NITROGÊNIO

A technique was developed for labeling the leguminous plant tissue with nitrogen (15N) to obtain labelled material for nitrogen dynamic studies. Sunnhemp (Crotalaria juncea L.) and velvet beans (Mucuna aterrima, sinonimia Stizolobium aterrimum Piper & Tracy) were grown in pots containing 10 kg of a Red Yellow Podzolic soil, under greenhouse conditions. The rate of 1.2 g of nitrogen (ammonium sulphate with 11.37 atom % 15N) per pot was applied three times. The labelled dried plant material showed 3.177 and 4.337 of atom % 15N, respectively for velvet beans and sunnhemp.

Nitrogen mineralization in soils amended with sunnhemp, velvet bean and common bean residues

Nitrogen (15N) released from sunnhemp (Crotalaria juncea), velvet bean (Mucuna aterrima) and from Phaseolus bean residues was evaluated after incubation of the plant material in an Eutrudox and a Paleudalf, in a greenhouse experiment with pots containing 6 kg of air dried soil. Dry matter equivalent to 13 Mg ha-1 of Phaseolus bean residues and the same amount of above ground parts of the leguminous species, associated to 2.7 and 2.2 Mg ha-1 of roots of sunnhemp and velvet bean respectively, were incorporated into the soil. A completely randomized experimental design was adopted, with treatments arranged in a 2 ´ 3 + 1 factorial, replicated three times. The treatments were the following: two soils (Eutrudox and Paleudalf) and three plant materials: two green-manures (sunnhemp or velvet bean), and Phaseolus bean residues, besides one control without plant incorporation into the soil. For the green-manure treatments there were two sub-treatments for each legume species, with 15N labeling of either shoots or roots. Soil moisture was maintained relatively constant during the experiment al period and the treatments were sampled weekly during 49 days. Total mineral nitrogen in the soil, as well as that derived from the legume plants were determined by isotope dilution. Nitrogen from the velvet bean accounted for a greater proportion of the soil inorganic N; shoots were responsible for most of N accumulated. Dry bean residues caused immobilization of inorganic N. The leguminous species added were intensively and promptly mineralized preserving the soil native nitrogen. Mineralization of the legume plant N was greater in the Paleudalf soil than in the Eutrudox.