Crops production in a fire-free system for land preparation in the northern Brazilian Amazon

Abstract Fire is traditionally used by smallholders for land preparation in the Brazilian Amazon but burning fallow vegetation has many disadvantages that lead to soil degradation. A fire-free system, based on slash-andmulch of fallow vegetation, has been studied as alternative for site preparation. The technique was considered feasible in the region of eastern Brazilian Amazon, even with the inputs of inorganic fertilizers. However, is very important to verify if a fire-free land preparation system is also feasible in other regions of the Brazilian Amazon. The aim of this study was to evaluate the fire-free system in the Mucajai region of northern Amazon in Brazil. Crop production was measured as a result of lime and low doses of fertilizers applied on the surface of mulch layer. In the first cropping period an intercropped system was evaluated simulating a strategy that will guarantee the diversity of products in the smallholdings. However, the combination between rice and corn was not adequate because while lime and fertilizers application improved rice yield, corn yield decreased due to competition. Both in first and second cropping periods, inorganic fertilizer application was essential to ensure higher grain production. Inorganic fertilizers were much more effective in association with liming

Doses and forms of application of phosphorus in vernalized garlic

Devido à baixa mobilidade do fósforo no solo, o estudo do efeito de sua localização em relação ao sistema radicular tem grande significado prático, principalmente em solos com deficiência extrema de fósforo. Experimentos com hortaliças dentro dessa abordagem têm sido pouco freqüentes. O presente trabalho estuda o efeito de doses e da localização do fertilizante fosfatado sobre o estado nutricional e a produção de bulbos de alho vernalizado (Allium sativum L.), bem como sobre atributos químicos do solo. Instalaram-se dois experimentos em vasos (16 dm³) com amostras de um Neossolo Quartzarênico Distrófico e de um Latossolo Vermelho Distroférrico, em esquema fatorial com quatro doses de fósforo (50, 100, 200 e 400 mg P dm-3) e cinco localizações em relação à incorporação (I) ou à aplicação no sulco (S), sendo L1= 100%I, L2= 75%I e 25%S, L3=50%I e 50%S, L4= 25%I e 75%S e L5= 100%S. As doses e as formas de aplicação do fósforo influenciaram os teores de fósforo extraído por resina e na folha das plantas em ambos os solos. A produção de bulbos aumentou com as doses de fósforo e foi influenciada pela localização do fertilizante fosfatado apenas no solo argiloso.Because of low P mobility in the soil, the effect of its position in relation to the root is of great practical significance, especially in soils with extreme P deficiency. Experiments with vegetables under this approach are not frequent. This work studies the influence of the position of phosphate fertilizer on nutrient absorption and on the production of vernalized garlic (Allium sativum L.) bulbs. Two experiments were carried out in pots (16 L) containing samples of a Typic Quartzipsamment and of a Typic Hapludox in a factorial scheme with four P doses (50, 100, 200, and 400 mg P dm-3) and five positions relative to the incorporation (I) or furrow application (S), where L1 = 100%I, L2 = 75%I and 25%S, L3 = 50%I and 50%S, L4 = 25%I and 75%S, and L5 = 100%S. Doses of fertilizer and forms of application influenced contents of phosphorus extracted by resin and from plant leaves, in both soils. Bulb yield increased with increasing P doses, and was influenced by the fertilizer's position only in the clayey soil

Carbon and chemical fractionation of soil organic matter in irrigated banana plantation subjected to conservation practice / Carbono e fracionamento químico da matéria orgânica do solo em bananal irrigado submetido à prática conservacionista

Irrigation and the use of cover crops are management practices that contribute to agriculture in regions with edaphoclimatic restrictions. The mentioned practices might affect the soil organic matter (SOM). In this context, the objective of this study were to evaluate the levels of total organic carbon (TOC), as well as the carbon in the chemical fractions of the SOM in an irrigated banana plantation submitted to soil conservation practice. The study was conducted at the experimental farm of the Federal University of Ceará, in the municipality of Pentecoste (Ceará, Brazil). The design was in randomized blocks, with split-split plot and four replicates. In the plots, four irrigation levels were evaluated; in the subplots, four soil coverings and in the sub-subplots two soil depths were evaluated. The superficial layer of soil associated with both legume Pueraria phaseoloides as cover crop and smaller irrigation level, showed higher TOC content (19.2 g kg-1). The highest amount of C was found in the fulvic acid fraction of SOM (3.8 to 6.2 g kg-1) regardless of the irrigation level and soil cover. The irrigation level that provided up to 75% of the evapotranspiration of the banana, combined with the legume Pueraria phaseoloides as cover crop provided higher contents of TOC, most of which were concentrated in the fulvic acid fraction of SOM. 

STRATEGIES THAT FAVOR MYCORRHIZATION IN THE REFORESTATION OF A DISTURBED AREA IN THE SEMIARID REGION

Hydrogel and mulch added to the soil may favor arbuscular mycorrhizal fungi (AMF), contributing to the reforestation of disturbed lands in semiarid regions. This study aimed to evaluate AMF colonization in the roots of Enterolobium contortisiliquum (Vell.) Morong in response to the application of hydrogel and mulch (bagana) from carnauba palm (Copernicia cerifera L.) to the soil and their effects in the soil and plants. A field experiment was set up in April 2014 in Ibaretama (Ceará, Brazil) in a randomized block design in a 2×4 factorial scheme – with mulch (+M) e without mulch (−M) × hydrogel doses (0, 4, 5, and 6 g L−1) –, with five replicates. Samples of roots, soil, and leaves were collected 18 months after the beginning of the experiment to determine AMF colonization in the roots and nutrient contents in the soil and plant material. The hydrogel dose of 6 g L−1 and mulch application equivalent to 10 Mg ha−1 increased AMF colonization by 21 e 44%, respectively. Soil contents of Ca, K, and Zn decreased with hydrogel doses without mulch but increased in the presence of the carnauba palm residue applied as mulch. A higher P content in the plant material was not associated with AMF colonization. The leaf content of Ca responded only to the treatment with mulch, reaching the highest value (3.8 g kg−1) in the absence of mulch

Resposta de duas cultivares de arroz a doses de zinco aplicado como oxissulfato

The objective of this work was to evaluate the effect of doses of Zn oxysulfate in granular and powder forms on two rice cultivars in a Red Latosol (Hapludox). The trial was carried out in a greenhouse in pots with 3 dm3 of soil. Lime, macronutrients and micronutrients except Zn were applied in all pots. Zinc rates were 0, 1, 2, 5 and 10 mg dm-3 of soil. Four mg Zn dm-3 were used as a standard source of this nutrient. A completely randomized design with four replicates was used. Powder oxysulfate in the cultivar IAC 165 and the granular one in IAC 202 resulted grain yields similar to those obtained with Zn sulfate used as standard. There were differences in the Zn concentration in leaves and culms of the cultivars as associated to the higher grain production. IAC 202 was more efficient in the use of Zn for vegetative growth and grain yield. Available soil Zn extracted either by Mehlich 1 or DTPA showed significant correlation with the doses of Zn applied and with the Zn tissue content. There was significant correlation between Zn levels as evaluated by both extracting solutions.O objetivo do trabalho foi avaliar o efeito de doses de Zn, aplicado como oxissulfato, nas formas granulada e em pó, em duas cultivares de arroz. O experimento foi realizado em casa de vegetação em vasos com 3 dm3 de um Latossolo Vermelho distrófico. Todos os vasos receberam calcário, macronutrientes e micronutrientes, com exceção do zinco. Foram aplicadas as doses de 0, 1, 2, 5 e 10 mg de Zn por dm3 de solo. A dose de 4 mg dm-3 de Zn aplicado como sulfato foi usada como padrão de referência. O delineamento experimental utilizado foi o inteiramente casualizado com quatro repetições. O oxissulfato em pó na cultivar IAC 165 e granular na IAC 202 possibilitaram produções de grãos semelhantes às obtidas com o sulfato de zinco. Houve diferença nos teores de Zn nas folhas e colmos das duas cultivares associados à maior produção de grãos. A cultivar IAC 202 foi mais eficiente na utilização de Zn no crescimento vegetativo e na produção de grãos. Os teores de Zn extraídos por Mehlich 1 e DTPA correlacionaram-se significativamente com as doses de Zn aplicadas e com os níveis de Zn no tecido vegetal. Houve correlação significativa entre os dois extratores em relação às doses de Zn aplicadas no solo

Potential of superabsorbent hydrogels to improve agriculture under abiotic stresses

Hydrogels are a promising management option to increase the efficiency of water use in agriculture in arid and semi-arid regions. However, abiotic factors may affect hydrogel efficacy. The effect of abiotic stress on the swelling and residual acrylamide in hydrogels was evaluated. The treatments were three hydrogels (A, B and C), four temperatures (20, 30, 40 and 65 °C) and two salinities (0.003 and 3.0 dS m−1). The swelling degree and the residual acrylamide concentration of the hydrogels were measured. Data were analyzed with univariate and multivariate statistics. The swelling order of hydrogels under low salinity was A>C>B; at high salinity was B>A>C. All hydrogels presented swelling reduction at high salinity, with swelling reductions in A and C of 97% and 85%, respectively, while B presented a swelling reduction of 37% at 20 °C and greater than 89% at higher temperatures. Hydrogel B achieved good swelling under saline conditions, but only at 20 °C. Thus, the temperature tolerance of this hydrogel should be improved so it can be used to improve water use efficiency in regions with high temperatures and salinity levels. Residual acrylamide levels of hydrogels decreased by 95% over 30 days, being safe for agricultural application

Adapting the land agricultural suitability assessment scheme for drylands edaphoclimatic conditions

ABSTRACT The rational exploitation of the land requires planning its agricultural use, which can be supported by the agricultural land suitability (ALS) assessment. The scheme to assess ALS proposed by Food Agricultural Organization (FAO) has been adopted in Brazil based on guiding charts for subtropical, humid tropical and semi-arid tropical climate. However, the guiding chart used for the semi-arid region has dramatically limited the ALS in drylands on which rainfed agriculture has been practiced. In this study, an adequation for the ALS assessment regarding the edaphoclimatic conditions of semi-arid region was proposed to improve the representation of agricultural areas and to allow a better planning of soil conservation practices. The ALS of the south region of Ceará State (Brazil) was assessed according to the FAO scheme and its initial adaptation to the Brazilian conditions; subsequently, this assessment was obtained by two adequations. Adequation I disregarded the limiting factor of water availability, while adequation II, besides disregarding the factor of water availability, established new limits for the classes of effective soil depth. The adequations resulted in an increase of 177.19 % in the areas with regular suitability for crops to the detriment of areas with restricted suitability for crops and areas with suitability only for pasture or grazing lands. The adequations increased the agricultural suitability in 41.26 % of the area of the mapping units, and 16.77 % of them were due to the modifications related to the effective soil depth, while the other 26.35 % were due to the changes related to water availability. The results related to water availability were equivalent to those observed through the dynamic analysis of land-use and cover associated with the rainfall, which demonstrated an increase in the areas for rainfed agriculture and a reduction in fallow and pasture areas in the years with rainfall within the climatic normality. The areas considered suitable for crop production with the adequation of the scheme may be included in soil conservation programs