resumo em sistemas de produção como a integração lavoura-pecuária (ilP) em sistema plantio direto (sPd) têm sido observadas melhorias nos atributos químicos, físicos e biológicos do solo. sendo assim, objetivou-se avaliar as alterações nos atributos químicos e físicos do solo e o acúmulo de carbono (C) num Latossolo Vermelho distrófico típico argiloso utilizado em sistema de ilP em sPd com irrigação, no cerrado. o delineamento experimental utilizado foi de blocos casualizados, com quatro repetições. os tratamentos foram dispostos em parcelas subdivididas no tempo, e as parcelas experimentais foram compostas pelas culturas do milho e do sorgo forrageiro cultivadas exclusivamente ou consorciadas com as espécies forrageiras Urochloa brizantha cv. Xaraés e Megathyrsus maximum cv. tanzânia para ensilagem; pelas espécies forrageiras no período de entressafra; e pela cultura da soja em sucessão. ForamRecebido para publicação em 13 de maio de 2014 e aprovado em 29 de outubro de 2014.

Agricultural management systems are needed to simultaneously enhance production, promote plant diversity, improve nutrient cycling and reduce soil compaction. We investigated the effects of intercropped forage grass on production of corn (Zea mays L.) harvested for silage at 0.20 and 0.45 m height in the summer, as well as on production of subsequent forage, soybean [Glycine max (L.) Merr.] harvested for silage, nutrient cycling and soil responses on a Typic Haplorthox in Botucatu, São Paulo State, Brazil. Palisade grass cv. BRS Piatã [Urochloa brizantha cv. BRS Piatã] was the introduced companion crop with corn (Years 1 and 2), while signal grass [Urochloa decumbens cv. Basilisk] was the residual weedy species in comparison. Guineagrass cv. Aruãna [Megathyrsus maximus cv. Aruãna] was the introduced companion crop with soybean (Year 3), with only a residual effect of crop systems from the previous two years. After the corn silage harvest, pasture was grazed by lambs in winter/spring using a semi-feedlot system. When cut at 0.45 m compared with 0.20 m height, corn intercropped with palisade grass had greater leaf nutrient concentration, improved agronomic characteristics, forage mass of pasture for grazing by lambs, greater surface mulch produced, and greater quantity of N, P and K returned to soil. Greater soil organic matter, P, K and Mg concentration, and base saturation in the surface soil depth and lower soil penetration resistance at all depths occurred at 0.45 m than at 0.20 m corn silage cutting height intercropped with palisade grass. Analyzing the system as a whole, harvesting corn silage crop with palisade grass intercrop at 0.45 m height was the most viable option in this integrated crop-livestock system.

Cattle excreta and nitrogen (N) fertilizer deposited on tropical grasslands are important sources of ammonia (NH 3) emission. We conducted three field trials (wet, intermediate, and dry conditions) to quantify NH 3 emissions from urea fertilizer and simulated excretions of heifer urine and dung on warm-climate grasslands in Brazil. Heifer excreta were derived from pastures of palisadegrass [Urochloa brizantha (Hochst. ex A. Rich.) R. D. Webster 'Marandu'] under three forms of N supply (without or with N fertilization [0 or 150 kg N ha −1 yr −1 ] or mixed with forage peanut [Arachis pintoi 'Amarillo']). Cumulative NH 3-N emissions across rainfall conditions were 7.6-16.6% (mean, 11.7%) for urine, 1.4-2.9% (mean, 2.0%) for dung, and 11.2-20.5% (mean, 14.8%) for urea. Ammonia loss from urine was significantly greater than from dung under all rainfall conditions. Emission from urine and dung differed from those when urea was applied on palisadegrass. There were greater NH 3 emissions from urine in the wetter times of the year. Heifer excreta from N-fertilized pasture had greater NH 3 emission than excreta from the grass-legume mixture and unfertilized palisadegrass. Urea applied on palisadegrass presented greater NH 3 emissions in wet rainfall conditions compared with dry conditions but did not differ from intermediate conditions. Our study showed that N-fertilized systems increase N losses as NH 3 emission from excreta, and emissions from urea fertilizer must be included in this system. Heifer excreta and urea fertilizer deposited on warm-climate grasslands increased the NH 3 emissions mainly under wet conditions.

Livestock production systems are an essential agribusiness activity in Brazil, but a critical challenge of Brazilian farmers is to maintain the equilibrium of the ecosystem, using herbage resources efficiently with a minimum impact on the environment. Nitrogen (N) fertilization and the inclusion of forage legumes into tropical grass pastures are management strategies which increase the productivity and nutritive value of pastures and may also affect methane (CH4) production by ruminants. The objective of this study was to examine the effects of either fertilizing palisade grass pastures with N or including the forage peanut (Arachis pintoi) into grass pastures on enteric CH4 emission, microbial protein production in the rumen via purine derivatives in the urine, and N balance. Twenty-one nonlactating crossbred dairy heifers were used in a completely randomized design with 3 treatments. The treatments consisted of pastures of palisade grass without N fertilization (control), fertilized with urea (fertilized), and palisade grass mixed with forage peanut (mixed). Seven animals (replications) were used to evaluate dry matter intake, digestibility, CH4 emission, urea, purine derivatives, and volume of urine, and N ingestion and excretion. Four paddocks (replications) were used to measure herbage mass; morphological, botanical, and chemical composition of herbage; and herbage allowance. The CH4 emissions were determined using the sulfur hexafluoride (SF6) tracer gas technique. The efficiency of N utilization (ENU) was calculated using the N balance data. Crude protein (CP) concentration of herbage increased with fertilization or legumes inclusion (P < 0.0001) while neutral detergent fiber (NDF) concentration decreased (P = 0.0355). The leaf allowance was higher in the fertilized treatment (P = 0.0294). Only uric acid excretion increased with N fertilization (P = 0.0204). The ENU was not affected by fertilized or mixed compared to control and averaged 55% (P = 0.8945). The enteric CH4 production was similar between treatments and averaged 129 g/d (P = 0.3989). We concluded that the changes in chemical composition of herbage provided by N fertilization or the inclusion of the legume showed no reduction in enteric CH4 emissions, but the ENU was more significant than previous studies with palisade grass, suggesting that different management strategies might alter the ENU under grazing conditions.

-Corn is a nitrogen-intensive crop, and the use of management practices such as inoculation of the seed with diazotrophic bacteria, which can maximize crop productivity and reduce the need of nitrogen fertilizers, may result in lower production costs. The present study aimed to evaluate the effect of inoculation of corn seed with Azospirillum brasilense and controlled addition of nitrogen to topdressing on the nutrition, production components, and productivity of crop grain. The experimental design was a randomized block design, with four replications in a 2 × 5 factorial scheme. The treatments consisted of inoculation or not of corn seed with A. brasilense (at 100 mL per 25 kg of seed) and five nitrogen (N) levels in topdressing (0, 30, 60, 90, and 120 kg N ha -1 from urea [45% N]) were applied when the corn was in the phenological growth stage V6. Foliar macronutrients, foliar chlorophyll index (FCI), production components, and yield of corn grain were valuated. Inoculation of corn seeds with A. brasilense increased plant height and grain yield. Fertilization in topdressing, with N levels up to 120 kg ha -1 , linearly increased the foliar nutrients and productivity of corn cultivated in the spring/summer in the low-altitude Cerrado region of Brazil.Keywords: Azospirillum brasilense. Zea mays. nitrogen. no-tillage system. INOCULAÇÃO DE BACTÉRIA DIAZOTRÓFICA E ADUBAÇÃO NITROGENADA DECOBERTURA EM MILHO IRRIGADO RESUMO -O milho é uma cultura exigente em nitrogênio e a utilização de práticas de manejo como a inoculação das sementes com bactérias diazotróficas, poderão maximizar a produtividade da cultura, atrelados a redução do uso de adubos nitrogenados, podendo refletir em menor custo de produção. O presente trabalho objetivou avaliar o efeito da inoculação de sementes de milho com Azospirillum brasilense e adição controlada de nitrogênio em cobertura sobre a nutrição, componentes da produção e produtividade de grãos da cultura. O delineamento experimental foi o de blocos casualizados, com quatro repetições, em esquema fatorial 2 x 5. Os tratamentos foram constituídos pela inoculação ou não das sementes do milho com A. brasilense (dose de 100 mL para 25 kg de sementes) e cinco doses de nitrogênio (N) em cobertura (0, 30, 60, 90 e 120 kg N ha -1 fonte ureia [45% N]) foram aplicadas quando o milho estava no estádio fenológico V6. Teores de macronutrientes foliares, o índice de clorofila foliar (FCI), os componentes da produção e a produtividade de grãos do milho foram avaliados. Constatou-se que a inoculação das sementes de milho com A. brasilense incrementou a altura de plantas e a produtividade de grãos. A adubação em cobertura, com a dose de até 120 kg N ha -1 , aumentou linearmente os teores nutricionais foliares e a produtividade de grãos do milho irrigado cultivado na primavera/ verão na região de Cerrado de baixa altitude do Brasil.Palavras-chave: Azospirillum brasilense. Zea mays. nitrogênio. sistema plantio direto.

The objective of this study was to evaluate the performance, feeding behavior, carcass traits, and meat quality of feedlot lambs using 2 types of silage, sorghum or soybean. Twenty-eight male non-castrated market lambs weighting 20 ± 2 kg were used. Diets were formulated to be isonitrogenous and isocaloric. The animals were slaughtered after 50 days of experiment, with 32.13 ± 5.09 kg of body weight. Lambs fed with soybean silage showed increased time for feed intake (P = 0.01). There was no difference for allowed daily gain, dry matter intake, feed conversion, and carcass traits between diets. Meat from lambs fed with soybean silage showed decreased shear force (P = 0.001) compared to sorghum silage, with no differences (P > 0.05) for chemical composition, color, and cooking loss. The intake of sorghum silage increased (P < 0.05) C6:0, C16:0, C20:0, C14:1, and C16:1 fatty acids content of Longissimus lumborum intramuscular fat. The intake of soybean silage showed an increased (P < 0.05) content of C18:1ω9t, C18:2ω6c, and sum of ω6 fatty acids. The feed cost and profit from the use of sorghum and soybean silage were US$ 0.

Nitrogen (N) management affects herbage production and chemical composition; however, information on the impact of tropical herbage on N and carbohydrate fractions is scarce. A two-year study was conducted to investigate the potential use of pintoi peanut (Arachis pintoi) compared with N fertilization of palisade grass (Brachiariabrizantha cv. Marandu) by evaluating the herbage chemical composition (fractionation of protein and carbohydrate), herbage mass and accumulation rate, herbage disappearance rate, and stocking rate of pastures. The experiment was conducted in a completely randomized design with three treatments, and four replications (paddocks) were used with twenty-one non-lactating crossbred dairy heifers. Treatments consisted of pastures of palisade grass without a N source (control), fertilized with urea (150 kg/ha/year; fertilized), or mixed with pintoi peanut (mixed). Inclusion of the legume increased concentrations of fractions A (p = 0.009), which is the soluble N compound, and B3 (p < 0.001), which is slowly degraded true protein, compared with pastures fertilized with N and non-fertilized pastures. Nitrogen fertilization increased fraction B1 + B2 (p = 0.046), mainly true proteins, and decreased fraction C (p = 0.0007), indigestible protein, and neutral detergent fiber concentrations (p = 0.0003), contributing to increasing the nutritive value of the herbage. Additionally, N fertilization increased herbage mass (p = 0.004) and herbage allowance (p = 0.0001). Both N fertilization and biologically fixed N increased herbage allowance (p = 0.02) and accumulation rate (p = 0.02), as well as the crude protein content of herbage (p < 0.0001) compared with non-fertilized pastures. Nitrogen fertilization increased true protein and decreased indigestible protein of herbage and promoted a greater herbage mass production, while the inclusion of legumes increased soluble protein and decreased the slowly degraded true protein of herbage. Both N management strategies increased herbage allowance and accumulation rate.

Palisadegrass [Urochloa brizantha (Hochst. ex A. Rich.) R. D. Webster cv. Marandu] is widely used in Brazil and is typically managed with little or no N fertilizer, which often leads to pasture decline in the long-term. The current relationship between beef price and fertilizer cost in Brazil does not favor fertilizer use in pastures. Legume inclusion is an alternative to adding fertilizer N, but often legumes do not reach a significant proportion (> 30%) in pasture botanical composition. This study evaluated herbage responses to N inputs and pasture species composition, under intermittent stocking. Treatments included palisadegrass-forage peanut (Arachis pintoi Krapov. & W.C. Greg. cv. Amarillo) mixture (mixed), unfertilized palisadegrass (control), and palisadegrass fertilized with 150 kg N ha-1 yr-1 (fertilized). Treatments were applied over two rainy seasons with five growth cycle (GC) evaluations each season. Response variables included herbage biomass, herbage accumulation, morphological components, total aboveground N of forage peanut (TAGNFP), and contribution of biological N2 fixation (BNF). Herbage biomass was greater for fertilized palisadegrass [5850 kg dry matter (DM) ha-1] than for the palisadegrass-forage peanut mixture (3940 kg DM ha-1), while the unfertilized palisadegrass (4400 kg DM ha-1) did not differ from the mixed pasture. Nitrogen fertilizer increased leaf mass of palisadegrass (2490 kg DM ha-1) compared with the control and mixed treatments (1700 and 1310 kg DM ha-1, respectively). The contribution of BNF to the forage peanut ranged from 79 to 85% and 0.5 to 5.5 kg N ha-1 cycle-1. Overall, benefits from forage peanut were minimal because legume percentage was less than 10%, while N input in the system by N-fertilizer increased palisadegrass herbage biomass.