Jeferson Dieckow

Integração lavoura-pecuária: intensificação de uso de áreas agrícolas

Crop-livestock is a production system that succeeds, at the same area, pastures to animal production and vegetal crops, especially cereals. The objective of this work was to discuss the major presuppositions and characteristics of the crop-livestock system in Southern Brazil, and its effects on the soil quality and animal and vegetal yield. This production system can result in some advantages to farmers such as increase of rent per area, higher diversification, decrease of economic hazards and production costs. Moreover, the crop-livestock system can show biological advantages such as biodiversity increase and improved soil quality. Among the disadvantages, it can point out the possibility of superficial soil compaction in inappropriate pasture management. To success of crop-livestock system some presuppositions must be considered, such as crop rotation, use of no-tillage system, correction of soil acidity and fertility, use of improving vegetal and animal genotypes and, mainly, adequate pasture management.

Cover Crop Effects Increasing Carbon Storage in a Subtropical No‐Till Sandy Acrisol

The long‐term (8‐year) effects of summer (Mucuna spp.) and winter cover crops (Avena strigosa + Vicia sativa and Lolium multiflorum + Vicia sativa) in maize‐based cropping systems on the total, particulate, and mineral‐associated soil carbon (C) stocks in the 0‐ to 0.2‐m layer of a no‐till South Brazilian Acrisol (87 g kg−1 clay) were evaluated. Annual C sequestration rates and the carbon management index (CMI) were calculated taking a fallow/maize (F/M) system as reference. A greater average C sequestration rate (0.68 Mg ha−1 yr−1) and greater C lability (particulate C/mineral‐associated C) were observed in the soil under the Mucuna system, and this was related to the higher biomass input in comparison to the winter cover crop systems. These cropping system effects on amount and lability of soil C were summarized through the CMI. The results highlight the potential of C retention in soils under warm and humid subtropical climate through the adoption of high C input summer cover crops in no‐till production systems aimed at further improvement in soil and environmental quality.

Soil quality assessed by carbon management index in a subtropical Acrisol subjected to tillage systems and irrigation

The combined influence of no-till and irrigation on soil quality in tropical and subtropical regions is still to be better clarified. The objective of this study was to evaluate the influence of sprinkler irrigation on soil quality of a southern Brazilian sandy loam Paleudult subjected to conventional tillage and no-till for 8 years. The soil quality indicator was the carbon management index (CMI), based on variations in the total C stock (expressed by the C pool index, CPI) and in the C lability (expressed by the C lability index, LI) related to the reference native grassland soil. The C lability was given by the ratio between the concentration of labile C, separated with NaI solution (1.8 Mg/m3), and non-labile C, obtained from the difference between total C and labile C. The total C stock, and thus the CPI, in the 0–200 mm layer were affected neither by tillage system nor by irrigation. On the other hand, the concentration of labile C, and thus the C lability and LI, were lower in conventional tillage than in no-till, and in irrigated than in non-irrigated systems. The effect of irrigation in decreasing the C lability was more pronounced in no-till than in conventional tillage soil. A combination of residue accumulation and greater water availability on the no-till soil surface probably provided suitable conditions to increase microbial mineralisation activity on the light fraction of the organic matter. The results of CMI, whose variations were caused mainly by LI, indicate that soil quality was improved with adoption of no-till in substitution of conventional tillage, but not with adoption of irrigation. No-till soils subjected to irrigation require a higher phytomass addition than non-irrigated soils.

Comparison of carbon and nitrogen determination methods for samples of a Paleudult subjected to no-till cropping systems

Organic carbon (C) concentration evaluated by the Walkley-Black method, and total nitrogen (N) concentration determined by Kjeldahl method, were compared with corresponding results of C and N concentrations obtained through the dry combustion method (Elementar Vario EL analyzer), using samples of ten soil layers down to the depth of 107.5 cm of a kaolinitic Typic Paleudult (220-418 g clay kg -1 along the profile) subjected to no-till cropping systems (fallow bare soil, pigeon pea (Cajanus cajan L. Millsp.) plus maize, and lablab (Lablab purpureum L. Sweet) plus maize). A close correlation (R 2 ≥ 0.96) was observed between the C results of the Walkley-Black and dry combustion methods, but a correction was suggested to be applied to C results of Walkley-Black (C = 1.05C W.Black + 0.47). A close correlation (R 2 ≥ 0.96) was also found between results of Kjeldahl-N and dry combustion-N, but no correction was necessary to be applied. The relationships between results of Walkley-Black and dry combustion and between results of Kjeldahl and dry combustion did not change among soil samples from different management systems, in disagreement to findings of a previous study where results of analytical C recovery were influenced by samples from different managements, supposedly because changes in lability or recalcitrance of organic matter might have affected the wet combustion reactions. A poor correlation (R 2 = 0.42) was found between the C:N ratios based on Walkley-Black and Kjeldahl analysis and the C:N ratios based on dry combustion analysis. The methods for C and N determination

Fracionamento físico da matéria orgânica e índice de manejo de carbono de um Argissolo submetido a sistemas conservacionistas de manejo

The physical fractionation of soil organic matter (SOM) is an alternative in assessing the amount of labile fraction that is used to calculate the carbon management index (CMI). The objective this research was to assess the efficiency of particle-size physical fractionation, (53-µm mesh), and density physical fractionation, with sodium iodide 1.8Mg m-3 (NaI) or sodium polytungstate 2.0Mg m-3 (PTS) solutions, at recovering SOM labile fractions (particulate and light, respectively) and at estimating the CMI. Soil samples of the 0-20cm layer of a sandy clay loam Acrisol under conventional tillage (CT) and no-tillage (NT) combined with two cropping systems (oat/maize and oat+vetch/maize+cowpea) were analyzed for stocks of total organic carbon (TOC), particulate organic carbon fraction (POC) and light fraction carbon (LF-C). In density physical fractionation, with the use of NaI was recovered less LF-C than PTS. The recovery of POC by particle-size fractionation was intermediate between the recovery of NaI-LF and PTS-LF. The CMI calculated after particle-size fractionation showed high correlation with CMI after density fractionation with NaI or PTS, although results were rather underestimated with NaI. Conservation management systems without soil disturbance and with higher crop residue addition enhanced the CMI, because of increments of both lability index and carbon pool index. The CMI based on SOM physical densimetrical fraction shows evidence of being and efficient index to discriminate management systems that can be used to assess soil management practices.

Organic N forms of a subtropical Acrisol under no-till cropping systems as assessed by acid hydrolysis and solid-state NMR spectroscopy

This study was conducted to investigate the influence of land-use systems (grassland and cropland) and of long-term no-till cropping systems [bare soil, oat/maize (O/M), pigeon pea+maize (P+M)] on the composition of organic N forms in a subtropical Acrisol. Soil samples collected from the 0- to 2.5-cm layer in the study area (Eldorado do Sul RS, Brazil) were submitted to acid hydrolysis and cross-polarization magic angle spinning (CPMAS) 15N and 13C nuclear magnetic resonance (NMR) spectroscopies. The legume-based cropping system P+M contained the highest contents of non-hydrolysable C and N, hydrolysable C and N, amino acid N and hydrolysed unknown N. The relative proportion of non-hydrolysable N was higher in bare soil (30.0%) and decreased incrementally in other treatments based on the total C and N contents. The amino acid N corresponded to an average of 37.2% of total N, and was not affected by land use and no-till cropping systems. The non-hydrolysable residue contained lower O-alkyl and higher aromatic C concentrations, as revealed by CPMAS 13C NMR spectroscopy, and higher C:N ratio than the bulk soil. No differences in the bulk soil organic matter composition could be detected among treatments, according to CPMAS 13C and 15N NMR spectra. In the non-hydrolysable fraction, grassland showed a lower concentration of aromatic and a higher concentration of alkyl C than other treatments. From CPMAS 15N NMR spectra, it could be concluded that amide N from peptide structures are the main organic N constituent. Amide structures are possibly protected through encapsulation into hydrophobic sites of organic matter and through organomineral interaction.

Different winter soil uses and their relation with weed infestation in maize (Zea mays) in succession

Economically viable alternatives for winter soil use in southern Brazil are scarce. During this period, pasture cultivated under crop-livestock system is an alternative. The objective of this study was to evaluate the effect of different winter soil uses on weed infestation in maize cultivated in succession. Two experiments were carried out from May, 2006 to April, 2007. Five alternatives of winter soil use were investigated: 1) multi-cropping with black oat + ryegrass + vetch + arrow leaf clover without grazing and nitrogen fertilization (multi-cropping cover);2) the same multi-cropping, with grazing and nitrogen fertilization, 100 kg ha-1 of N (pasture with N); 3) the same multi-cropping, with grazing and without nitrogen fertilization (pasture without N); 4) oil seed radish, without grazing and nitrogen fertilization (oil seed radish); and 5) natural vegetation, without grazing and nitrogen fertilization (fallow). Cover crop in the winter, cultivated without grazing, produces a high amount of straw, reducing weed summer infestation. Under the experimental conditions, winter soil use with pasture allows high weed summer infestation, due to the low amount of straw that stays on the soil.

Atributos de solo e cultura espacialmente distribuídos relacionados ao rendimento do milho

Precision agriculture can increase efficiency and sustainability of grain crops in Brazil, especially in support of soil and crop management. In this study the importance of spatially-variable soil and crop attributes on the variability of grain crop yield and the use of this information to improve management decisions was examined. The study used data from the 2005/6 corn growing season of a 18 ha commercial field on a clayey Latossolo Bruno (FAO: Ferralsol). Soil (0-0.10 m layer) and crop properties were sampled at a density of two per ha. Spatially distributed crop yield was determined with a grain sensor on the harvester. Yield variability (average of 12.4 Mg ha-1, amplitude between 11.1 and 14.0 Mg ha-1) was related to the soil properties - P Mehlich, Mg2+, sum of bases and Ca:Mg, Mg:K and Mg:CEC ratios - but not with crop attributes, according to the results of a Spearman correlation matrix. Regression analysis identified a critical value of Magnesium saturation (Mg:CEC) of 0.10, and a critical Mg:K ratio of 2.3, as the most significant soil properties. Below the critical values, yields were reduced. Cluster analysis confirmed the results obtained by the two previous statistical techniques, and their combined interpretation supported the conclusion that P and Mg were the two nutrients for which spatial management is most needed. Compared to the traditional fixed-rate, whole-field application, using variable rate application would require, for the whole field, 6.6 Mg of additional lime, being 3.4 Mg calcitic lime and 3.2 Mg dolomitic lime, less P2O5 (-235 kg), and more K2O (+ 135 kg) than in the normal uniform management. However, with variable rates such inputs would be applied at adequate rates to specific parts of the field, positively affecting the yields in these parts. When management decisions are supported by appropriate statistical tools, precision agriculture is technically viable for the management of soil chemical properties, allowing for optimized dosages, with a view to an ideal economical yield.

Desempenho da cultura do feijão após diferentes formas de uso do solo no inverno

O uso e manejo do solo durante o inverno pode alterar as caracteristicas fisicas do solo, a cobertura remanescente e o desempenho da cultura semeada em sucessao. O objetivo deste trabalho foi avaliar o efeito de formas de uso do solo no inverno sobre essas variaveis, semeando-se a cultura do feijao em sucessao, manejada em plantio direto. Na safra 2007/08, foram conduzidos tres experimentos na regiao do Planalto Norte Catarinense, onde foram avaliadas cinco formas de uso do solo durante o inverno: 1) consorcio de aveia preta + azevem + ervilhaca + trevo vesiculoso manejado sem pastejo e sem adubacao nitrogenada (consorcio cobertura); 2) o mesmo consorcio, com pastejo e com 100kg ha-1 de N em cobertura (pastagem com N); 3) o mesmo consorcio, com pastejo e sem adubacao nitrogenada (pastagem sem N); 4) nabo forrageiro, sem pastejo e sem adubacao nitrogenada (nabo forrageiro); e 5) pousio, sem pastejo e sem adubacao nitrogenada (pousio). O consorcio cobertura proporciona maior quantidade de palha para o cultivo de feijao em sucessao, mas as formas de uso do solo no inverno estudadas nao afetam expressivamente a densidade e a macroporosidade do solo. O uso do solo no inverno com pastagem anual em sistema integracao lavoura-pecuaria, coberturas de solo e pousio nao afeta o desempenho da cultura do feijao semeada em sucessao, manejada em plantio direto.

Water, Sediment and Nutrient Retention in Native Vegetative Filter Strips of Southern Brazil

Vegetative filter strips (VFS) are areas adjacent to watercourses with the purpose of reducing sediment and nutrients contained within runoff water from cropland. The aim of this study was to evaluate the retention of water, sediment and nutrients in VFSs with 5, 10, 20 and 30 m widths exposed to simulated runoff water. The VFS chosen for this study were populated by native herbaceous vegetation with a predominance of grasses from South of Brazil. To simulate runoff water, a flow of 30 L min -1 was applied to all plots. Simulated runoff water contained 3.22 g L -1 of sediment and the nutrients concentration was 62.2; 40.9 and 170.3 mg L -1 de P, NH 4-N and NO 3-N,