Nitrate role in basic cation leaching under no-till

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Produtividade de grãos de milho, produção de matéria seca e acúmulo de nitrogênio, fósforo e potássio na rotação aveia preta/milho/nabo forrageiro com aplicação de dejeto líquido de suínos

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Refuse production in leaf-cutting ants (Hymenoptera: Formicidae) and its relationship with leaf harvest

We examined the relationship between fungal refuse production and vegetation input in a laboratory colony of the leaf-cutting ant Acromyrmex coronatus. We found only a strong 6-day time-delay in the production of refuse with variation in substrate intake.

Early development and nutrition of cover crop species as affected by soil compaction

A good cover crop should have a vigorous early development and a high potential for nutrient uptake that can be made available to the next crop. In tropical areas with relatively dry winters drought tolerance is also very important. An experiment was conducted to evaluate the early development and nutrition of six species used as cover crops as affected by sub-superficial compaction of the soil. The plants (oats, pigeon pea, pearl millet, black mucuna, grain sorghum, and blue lupin) were grown in pots filled with soil subjected to different subsurface compaction levels (bulk densities of 1.12, 1.16, and 1.60 mg m(-3)) for 39 days. The pots had an internal diameter of 10 cm and were 33.5 cm deep. Grasses were more sensitive to soil compaction than leguminous plants during the initial development. Irrespective of compaction rates, pearl millet and grain sorghum were more efficient in recycling nutrients. These two species proved to be more appropriate as cover crops in tropical regions with dry winters, especially if planted shortly before spring.

Residual and annual potassic fertilization for soybeans

There is a lack of long-term research on potassium fertilization for soybean in the tropical and subtropical soils of Brazil and the residual effect of the fertilizer has generally not been considered. An experiment was conducted in plots that had been fertilized with 0, 40, 80, 160 and 240 kg ha(-1) of K2O for 3 years on a Dark Red Latosol, loamy sand (Acrortox). The effects of annual or residual fertilization with those rates of K were studied for three additional years. Potassium was supplied as potassium chloride or potassium sulphate. Soil and leaf samples were taken annually. There was a residual effect of the nutrient, which provided for high yields up to the 3rd year with the highest rate of K. In order to maintain the K contents of the soil in the medium range and obtain at least 90% of the maximum grain yield, an annual application of 80 kg ha(-1) of K2O was necessary, irrespectively of the source. The highest soybean yields were always associated with K levels above 15 mg kg(-1) in the leaves and 1.2 mmol(c) dm(-3) in the soil.

Leaching of nitrate and ammonium from cover crop straws as affected by rainfall

Nitrogen (N) mineralization dynamics in no-till systems is affected, among other factors, by N amount and quality in the mulch and by climatic conditions. Leaching of NO3-N and NH4-N from six plant species used as soil cover crops in tropical environments were evaluated when the straw was submitted to rainfall after chemical desiccation. Millet (Pennisetum glaucum), guinea sorghum (Sorghum vulgare), black oat (Avena strigosa), triticale (Triticum secale), Indian hemp (Crotalaria juncea), and brachiaria (Brachiaria decumbens) were grown in a greenhouse, in Botucatu-SP, Brazil. Forty-five days after emergence, the plants were cut at the root collar, oven-dried, and submitted to simulated rainfalls of 4.4, 8.7, 17.04, 34.9, and 69.8 mm, considering an amount of straw equivalent to 8 t ha(-1) of dry matter. The amounts of N-NO3- extracted from the straw by rainwater were very small. However, accumulated rainfall around 70 mm caused ammonium leaching ranging from 2.5 to 9.5kg ha(-1), depending on the species. Plant residues of triticale and black oat (grasses) and Indian hemp (legume) showed high N leaching intensity with the first rains after chemical desiccation. The amount of N leached from straw was highly correlated with N tissue content.

Persistência e liberação de macronutrientes e silício da fitomassa de crotalária em função da fragmentação

The persistence of straw, as well as the dynamics of nutrients release of it, are important aspects to consider in the choice of plants for composition of crop rotations in a no tillage system. Thus, the objective of this work was to evaluate the decomposition rate and macronutrients and silicon (Si) release from sunn hemp (Crotalaria juncea L.) phytomass, as a function of management, with and without fragmentation. A randomized blocks design, with four replications, in a factorial 2x6, constituted by two aboveground phytomass management after 75 days after emergence (with and without mechanical fragmentation) and six sampling times (0, 18, 32, 46, 74 and 91 days after management (DAM)), were evaluated the decomposition rate and nutrient release from sunn hemp biomass. The mechanical fragmentation of sunn hemp straw did not change the decomposition and macronutrients release. The maximum release rates occurred 0-18 DAM. Potassium is the most rapidly available nutrient, while the silicon is more slowly released to the ground. Over time there has been increasing Si content in the straw.

Performance of constructed wetland system for public water supply

The project is being conducted in the town of Analândia, São Paulo, Brazil. The constructed wetlands system for water supply consists of a channel with floating aquatic macrophytes, HDS system (Water Decontamination with Soil - Patent PI 850.3030), chlorinating system, filtering system and distribution. The project objectives include investigating the process variables to further optimize design and operation factors, evaluating the relation of nutrients and plants development, biomass production, shoot development, nutrient cycling and total and fecal coliforms removal, comparing the treatment efficiency among the seasons of the year; and moreover to compare the average values obtained between February and June 1998 (Salati et al., 1998) with the average obtained for the same parameters between March and June 2000. Studies have been developed in order to verify during one year the drinking quality of the water for the following parameters: turbidity, color, pH, dissolved oxygen, total of dissolved solids, COD, chloride, among others, according to the Ministry of Health's Regulation 36. This system of water supply projected to treat 15 L s-1 has been in continuous operation for 2 years, it was implemented with support of the National Environment Fund (FNMA), administered by the Center of Environmental Studies (CEA-UNESP), while the technical supervision and design were performed by the Institute of Applied Ecology. The actual research project is being supported by FAPESP.

Potassium leaching from millet straw as affected by rainfall and potassium rates

Pearl millet (Penisetum glaucum) is an interesting species to be used as cover crop in tropical areas, showing a high ability in potassium uptake. Potassium (K) is not linked to organic compounds in the plant, and can easily be released from decaying straw becoming available for subsequent crops. This experiment evaluated K leaching from millet straw grown under potassium rates (0, 100, 200, and 300 mg dm-3), and submitted to five levels of simulated rain (5, 10, 20, 40, and 80 mm). Plants were grown in soil filled pots in a greenhouse. On the 50th day after emergence, the plants were desiccated with glyphosate. Artificial rain was applied over the straw. Potassium deficiency speeds up millet dehydration after herbicide application and increases lightly rain water retention in the straw. The amount of K leached right after plant desiccation is correlated with the residue nutrient content and can be as high as 64 kg ha-1 considering a mulch of 8 t ha -1. Although well-nourished millet plants release considerable amounts of K with the first rains, a large percentage of the nutrient is still retained in the straw. Copyright © Taylor & Francis, Inc.

Mineralización de la paja de caña de azúcar en suelo adicionado con viñaza (suproducto de la industria del alcohol de caña de azúcar) y fertilizante nitrogenado

Cellulose is the most abundant vegetable organic compound, being derived mainly from plant residues. The decomposition of sugar-cane (Saccharum officinarum L.) straw was studied in a period up to 90 days, through variables related to the carbon cycle, such as respiratory activity and CM-cellulase (CM, cellulose microcrystalline) and CMC-cellulase (CMC, carboxymethylcellulose) activities. The treatments consisted of 0, 0.5 and 1.0% of straw, in the presence and absence of vinasse (a sugar-cane alcohol industry byproduct) and nitrogen fertilizer. The respiratory and cellulase activities increased up to the 14th day of incubation and later decreased. The respiratory activity was 1.9 and 2.3 fold larger (P < 0.05) in the soil with 0.5 and 1.0% of straw added, respectively, in relation to the control. CM- and CMC- cellulase activities also increased from 1.8 to 2.9 and from 2.3 to 2.7 fold, respectively. The vinasse addition enhanced CO 2 production and CM-cellulase activity, however, no significant effect was observed on CMC-cellulase activity. The addition of N reduced both respiratory and cellulase activities. The decomposition of the sugar-cane straw may enhance soil nutrient cycling increasing agricultural production. © 2006 Instituto de Investigaciones Agropecuarias, INIA.

Avaliação das propriedades químicas em solo de cerrado SOB reflorestamento ciliar

The rapid growth of agriculture, promoted by public government initiatives, favored an out of control deforestation of our forests; today, reforestation of permanent preservation areas are necessary for the conservation of our natural resources, and recovery of such areas are required by public laws. In an area of 5.26 acres of riparian reforestation in the savanna soil chemical properties were evaluated after twenty years of planting. It was analyzed the following variables: (P, organic matter (MO), pH, K, Ca, Mg, H+Al, Al and S) in 13 modules, with three replicas in two depths (0 - 20 and 20 - 40 cm) in a randomized block design in hierarchical scheme. Reforestation with tree species on the edge of Parana river in Selvíria (MS) contributes to chemical soil attributes, under riparian reforestation, as similar as a soil without human disturbance in this region; it is also possible to verify that forestry plantation promotes deposition of organic material which is essential for nutrient cycling, which keep the chemical properties of such soil in good condition for the establishment of riparian vegetation.

Phosphorus and potassium budget in the soil-plant system in crop rotations under no-till

Soil management and crop rotations can affect P and K budget in soil, decreasing losses, and increasing fertilizer use efficiency. The P and K budget in the soil-plant system at depths up to 60. cm was studied for different soil managements and crop rotations under no-till for three years in Botucatu, São Paulo, Brazil. The investigated crop rotations were: triticale (X Triticosecale) and sunflower (Helianthus annuus) cropped in autumn-winter; pearl millet (Pennisetum glaucum), forage sorghum (Sorghum bicolor), and Sunn hemp (Crotalaria juncea) were grown in the spring, as well as an additional treatment with chiseling followed by a fallow period; and soybean (Glycini max, L., Merril) was cropped in the summer. Each year triticale and sunflower were grown in plots and pearl millet, forage sorghum, Sunn hemp and of chisel/fallow in sub-plots. The triticale/millet rotation led to the largest decrease in available P within the 0-0.60. m layer of the soil profile and the largest K increase within the 0-0.05. m layer. Potassium mobility in the soil profile and the increases in the available K content in the 0.40-0.60. m layer were independent of the management system. Crop rotations with or without chiseling are not effective in preventing soil P losses. There is considerable K leaching below 0.60. m, but chiseling and the use of high K accumulating plants as triticale results in lower K losses. © 2012 Elsevier B.V.

The role of multiple partners in a digestive mutualism with a protocarnivorous plant

Background and aimsThe protocarnivorous plant Paepalanthus bromelioides (Eriocaulaceae) is similar to bromeliads in that this plant has a rosette-like structure that allows rainwater to accumulate in leaf axils (i.e. phytotelmata). Although the rosettes of P. bromelioides are commonly inhabited by predators (e.g. spiders), their roots are wrapped by a cylindrical termite mound that grows beneath the rosette. In this study it is predicted that these plants can derive nutrients from recycling processes carried out by termites and from predation events that take place inside the rosette. It is also predicted that bacteria living in phytotelmata can accelerate nutrient cycling derived from predators.MethodsThe predictions were tested by surveying plants and animals, and also by performing field experiments in rocky fields from Serra do Cipó, Brazil, using natural abundance and enriched isotopes of 15N. Laboratory bioassays were also conducted to test proteolytic activities of bacteria from P. bromelioides rosettes.Key ResultsAnalyses of 15N in natural nitrogen abundances showed that the isotopic signature of P. bromelioides is similar to that of carnivorous plants and higher than that of non-carnivorous plants in the study area. Linear mixing models showed that predatory activities on the rosettes (i.e. spider faeces and prey carcass) resulted in overall nitrogen contributions of 26·5 % (a top-down flux). Although nitrogen flux was not detected from termites to plants via decomposition of labelled cardboard, the data on 15N in natural nitrogen abundance indicated that 67 % of nitrogen from P. bromelioides is derived from termites (a bottom-up flux). Bacteria did not affect nutrient cycling or nitrogen uptake from prey carcasses and spider faeces.ConclusionsThe results suggest that P. bromelioides derive nitrogen from associated predators and termites, despite differences in nitrogen cycling velocities, which seem to have been higher in nitrogen derived from predators (leaves) than from termites (roots). This is the first study that demonstrates partitioning effects from multiple partners in a digestion-based mutualism. Despite most of the nitrogen being absorbed through their roots (via termites), P. bromelioides has all the attributes necessary to be considered as a carnivorous plant in the context of digestive mutualism. © 2012 The Author. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved.

Phosphorus and potassium balance in a corn-soybean rotation under no-till and chiseling

Nutrient use efficiency has become an important issue in agriculture, and crop rotations with deep vigorous rooted cover crops under no till may be an important tool in increasing nutrient conservation in agricultural systems. Ruzigrass (Brachiaria ruziziensis) has a vigorous, deep root system and may be effective in cycling P and K. The balance of P and K in cropping systems with crop rotations using ruzigrass, pearl millet (Pennisetum glaucum) and ruzigrass + castor bean (Ricinus communis), chiseled or not, was calculated down to 0.60 m in the soil profile for 2 years. The cash crops were corn in the first year and soybean in the second year. Crop rotations under no-till increased available P amounts in the soil-plant system from 80 to 100 %, and reduced K losses between 4 and 23 %. The benefits in nutrient balance promoted by crop rotations were higher in the second year and under without chiseling. Plant residues deposited on the soil surface in no-till systems contain considerable nutrient reserve and increase fertilizer use efficiency. However, P release from ruzigrass grown as a sole crop is not synchronized with soybean uptake rate, which may result in decreased yields. © 2013 Springer Science+Business Media Dordrecht.