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Due to environmental issues, many methods of exploiting renewable natural resources are alternatives to reduce the dependence on non‐renewable agricultural inputs. Phosphate fertilization on weathered tropical soil and waste reuse, for example, requires better management strategies. Thus, biochar from organic residues can be a strategy to reduce pressure on natural resources, in addition to having the potential to mitigate climate change. This study aimed to evaluate the availability of P in tropical soils from the interaction of biochar and arbuscular mycorrhizal fungi (AMF) in the aboveground and root systems of the plant and its impact on greenhouse gas (GHG) emissions. The results indicated that the addition of biochar was an alternative for C sequestration and GHG mitigation, causing no damage to the plant. The applied biochar amount had, for the most part, emission equal to or less than the control treatment (soil only). The sugarcane straw biochar (BCS) showed higher emissions, mainly in the presence of P and AMF. Biologically speaking, there was no significant effect in the presence of mycorrhizae. However, with regard to plant production, treatments where mycorrhizae were inoculated, longer and wider leaves were found. In the production of maize (Zea mays L.) plant material (aboveground and root), the upper and lower values were related to the poultry manure biochar (BPM) , and the presence of P, the values were lower, indicating that, for the good development of the plant, only the presence of the biochar is sufficient, without requiring the addition of phosphate fertilizer. [ABSTRACT FROM AUTHOR]

No information regarding the management of manure from beef cattle feedlots is available for Brazil. To fill this knowledge gap, a survey of 73 feedlots was conducted in 7 Brazilian states. In this survey, questions were asked regarding animal characteristics, their diets, and manure handling management from generation to disposal. These feedlots finished 831,450 animals in 2010. The predominant breed fed was Nellore, with average feeding periods of 60 to 135 d. Corn was the primary source of grain used in the feedlot diets (76% of surveyed animals) with concentrate inclusion levels ranging from 81 to 90% (38% of surveyed animals). The most representative manure management practice was the removal of manure from pens only at the end of the feeding period. Subsequently, the manure was stored in mounds before being applied to crop and pasture lands. Runoff, mainly from rainwater, was collected in retention ponds and used for agriculture. However, the quantity of runoff was not known. Manure was composted for only 20% of the animals in the survey and was treated in anaerobic digesters for only 1% of the animals. Manure from 59% of the cattle surveyed was used as fertilizer, providing a cost savings over the use of synthetic fertilizers. Overall, chemical analysis of the manure before application to fields was conducted for the manure of 56% of the surveyed animals, but the exact quantity applied (per hectare) was unknown for 48%. Feedlots representing 48% of the surveyed animals noted similar or greater crop and pasture yields when using manure, rather than synthetic fertilizers. In addition, 32% mentioned an increase in soil organic matter. Feedlots representing 88% of the surveyed cattle indicated that information concerning management practices that improve manure use efficiency is lacking. Feedlots representing 93% of the animals in the survey reported having basic information regarding the generation of energy and fertilizer with anaerobic digesters. However, only 1 feedlot implemented this technology. In conclusion, the manure management evaluated in this study represents an important indirect economic benefit that was represented by decreased use of synthetic fertilizers in crops. However, little attention was given to the specific treatments and environmental impacts of handling manure. This survey provides information that should assist in the development of better research practices and broader application of future models. [ABSTRACT FROM AUTHOR]

Agricultural management practices that promote net carbon (C) accumulation in the soil have been considered as an important potential mitigation option to combat global warming. The change in the sugarcane harvesting system, to one which incorporates C into the soil from crop residues, is the focus of this work. The main objective was to assess and discuss the changes in soil organic C stocks caused by the conversion of burnt to unburnt sugarcane harvesting systems in Brazil, when considering the main soils and climates associated with this crop. For this purpose, a dataset was obtained from a literature review of soils under sugarcane in Brazil. Although not necessarily from experimental studies, only paired comparisons were examined, and for each site the dominant soil type, topography and climate were similar. The results show a mean annual C accumulation rate of 1.5 Mg ha year for the surface to 30-cm depth (0.73 and 2.04 Mg ha year for sandy and clay soils, respectively) caused by the conversion from a burnt to an unburnt sugarcane harvesting system. The findings suggest that soil should be included in future studies related to life cycle assessment and C footprint of Brazilian sugarcane ethanol. [ABSTRACT FROM AUTHOR]

Due to the worldwide increase in demand for biofuels, the area cultivated with sugarcane is expected to increase. For environmental and economic reasons, an increasing proportion of the areas are being harvested without burning, leaving the residues on the soil surface. This periodical input of residues affects soil physical, chemical and biological properties, as well as plant growth and nutrition. Modeling can be a useful tool in the study of the complex interactions between the climate, residue quality, and the biological factors controlling plant growth and residue decomposition. The approach taken in this work was to parameterize the CENTURY model for the sugarcane crop, to simulate the temporal dynamics of aboveground phytomass and litter decomposition, and to validate the model through field experiment data. When studying aboveground growth, burned and unburned harvest systems were compared, as well as the effect of mineral fertilizer and organic residue applications. The simulations were performed with data from experiments with different durations, from 12 months to 60 years, in Goiana, Timbaúba and Pradópolis, Brazil; Harwood, Mackay and Tully, Australia; and Mount Edgecombe, South Africa. The differentiation of two pools in the litter, with different decomposition rates, was found to be a relevant factor in the simulations made. Originally, the model had a basically unlimited layer of mulch directly available for decomposition, 5,000 g m−2. Through a parameter optimization process, the thickness of the mulch layer closer to the soil, more vulnerable to decomposition, was set as 110 g m−2. By changing the layer of mulch at any given time available for decomposition, the sugarcane residues decomposition simulations where close to measured values ( R 2 = 0.93), contributing to making the CENTURY model a tool for the study of sugarcane litter decomposition patterns. The CENTURY model accurately simulated aboveground carbon stalk values ( R 2 = 0.76), considering burned and unburned harvest systems, plots with and without nitrogen fertilizer and organic amendment applications, in different climates and soil conditions. [ABSTRACT FROM AUTHOR]

Currently there is a trend for the expansion of the area cropped with sugarcane (Saccharum officinarum L.), driven by an increase in the world demand for biofuels, due to economical, environmental, and geopolitical issues. Although sugarcane is traditionally harvested by burning dried leaves and tops, the unburned, mechanized harvest has been progressively adopted. The use of process based models is useful in understanding the effects of plant litter in soil C dynamics. The objective of this work was to use the CENTURY model in evaluating the effect of sugarcane residue management in the temporal dynamics of soil C. The approach taken in this work was to parameterize the CENTURY model for the sugarcane crop, to simulate the temporal dynamics of soil C, validating the model through field experiment data, and finally to make predictions in the long term regarding soil C. The main focus of this work was the comparison of soil C stocks between the burned and unburned litter management systems, but the effect of mineral fertilizer and organic residue applications were also evaluated. The simulations were performed with data from experiments with different durations, from 1 to 60 yr, in Goiana and Timbaúba, Pernambuco, and Pradópolis, São Paulo, all in Brazil; and Mount Edgecombe, Kwazulu-Natal, South Africa. It was possible to simulate the temporal dynamics of soil C (R2 = 0.89). The predictions made with the model revealed that there is, in the long term, a trend for higher soil C stocks with the unburned management. This increase is conditioned by factors such as climate, soil texture, time of adoption oil the unburned system, and N fertilizer management. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the interrelationships and seasonal weather variations on soil total C and N concentrations, microbial biomass C pool, trace gas fluxes, and rates of internal N-cycling from soils under degraded pasture at Nova Vida ranch, Rondônia, Brazilian Amazon. We collected samples from soils and gas fluxes at the 5 soil types in April 2000 (end of the wet season) and in October 2001 (end of the dry season). Samples were analyzed in both seasons for soil microbial biomass C, soil total C and N, inorganic N, net N mineralization and net nitrification rates and some other soil properties. Overall, the effects of the season events upon soil properties were highly variable. The studied soils with high rates of CO2 evolution but low rates of net N mineralization had high rates of N immobilization. The high immobilization rates suggest that the high CO2 evolution rates were associated with a growing microbial biomass. Moreover, in the wet season, the lower NO3-N pools and rates of net mineralization and net nitrification we measured are indicative of lower pasture N1O fluxes. In general, net nitrification rates exceeded net N mineralization rates as the relatively NH4+-N pools. The interrelationships were investigated in order to understand the major biogeo-chemical cycles that influence soil fertility under pasture, which is important for devising management technologies that enhance the sustainability of these areas and thus slow further deforestation. [ABSTRACT FROM AUTHOR]

Attempts to map vegetation types, especially pasture, from satellite sensor data in tropical and sub-tropical regions very often have limited success. This study analyses the accuracy of two classifications of Landsat Thematic Mapper (TM), with the aim of distinguishing the pastures from other vegetation classes in a meso-scale basin (12 400 km[sup 2], Piracicaba basin, Brazil). The initial classification is based on non-supervised clustering of the images. The delimited classes are interpreted and merged by comparison with standard spectra from NASA. The second classification is a parallelepiped partition based on the merged clusters issued from the first one. The two classifications are compared by validation with 287 random field observations selected within the whole catchment. The results are discussed, analysing the spectral behaviour variability of the pasture class. [ABSTRACT FROM AUTHOR]