Mechanical analysis in some soils of the semi-arid region in Northeast Brazil: normal, calcareous, calcareous with soluble salts, and saline soils

O presente trabalho estuda a dispersão da fração argila (fração menor que 2 micra), em amostras de solo da Zona Semi-árida do Nordeste. Foram utilizados o hidróxido de sódio e o hexametafosfato de sódio como dispersante e o método da pipeta com utilização do Cilindro de Koettinge e Koettinge modificado. Foram estudadas 33 amostras de solo, assim distribuídas: 10 amostras de solos normais (sem sais solúveis e sem carbonatos); 16 amostras de solo calcário; 04 amostras de solo calcário com sais solúveis; 03 amostras de solo salino. Foram empregados os seguintes tratamentos: Trat. 1: sem tratamento. Trat. 2: com tratamento prévio da amostra pelo HCl a 10%. Trat. 3: com lavagem prévia da amostra pelo álcool etílico a 60%. Trat. 4: com lavagem prévia da amostra com água destilada. Os tratamentos foram feitos de acôrdo com a natureza do solo. Considerando os resultados obtidos com os dois dispersantes, para cada grupo de amostras e, levando-se em conta: a) os tratamentos indicados; b) as classes texturais das amostras (fornecidas pelos técnicos da Divisão de Pedologia e Fertilidade do Solo do Ministério da Agricultura); c) os maiores valores encontrados para a fração argila. São apresentadas várias conclusões, destacando-se entre elas as seguintes: I. Para solos normais (não calcários, não salinos e não alcalinos): é indiferente o emprêgo do NaOH ou do HEXA. II. Para solos calcários: o NaOH (Trat. 2) apresentou melhores resultados em tôdas as amostras. O HEXA (Trat. 1) apresentou resultados concordantes com a textura de campo, com exceção de uma amostra, mas com valores mais baixos para a argila, em relação ao NaOH (Trat. 2). III. Para solos calcários com sais solúveis: o NaOH (Trat. 2) foi o mais eficiente para as amostras estudadas. O HEXA com os Trat. 3 e 4 foi também eficiente. IV. Para solos salinos: em amostras com teores de sais solúveis baixos é indiferente o uso dos dois dispersantes com os Trat. 1, 3 e 4. Em amostras com elevados teores de sais solúveis, o HEXA é o indicado, com os Trat. 3 ou 4. O NaOH não deve ser empregado no Trat. 1.In this paper the author studies the dispersion of the 2 clay fractions of some soil samples of the semi-arid region in Northeast Brazil, aiming to test the effectiveness of sodium hydroxide and hexametaphosphate as dispersing agents in mechanical analysis of different kinds of soils, namely: normal calcareous, calcareous with soluble salts, and saline soils. Thirty three soil samples were used: 10 normal soils, 16 calcareous, 4 calcareous with soluble salts, and 3 saline soils. The following pre-treatments were employed: Treat. 1. no pre-treatment. Treat. 2. 10% HCl pre-treatment. Treat. 3. previous washing of sample with 60% alcohol ethylic. Treat. 4. previous washing of sample with distilled water. These pre-treatments were selected according to the nature of each group of soils, as follows: Normal soils: Pre-treatment 1. Calcareous soils: Pre-treatments 1 and 2. Calcareous with soluble salts: Pre-treatments 1, 2, 3, and 4. Saline soils: Pre-treatments 1, 3 and 4. Considering the results obtained with the 2 dispersing agents, and taking into account the following items: a) the pre-treatment used; b) the textural classification, as determined in the field; c) the highest value obtained for the 2 micra clay fraction. The author presents the following conclusions: I. Normal soils: The effectiveness of sodium hydroxide and sodium hexametaphosphate as dispersing agents is the same. II. Calcareous soils: Sodium hydroxide (Treat. 2) produced the best results. Except for one sample, the hexametaphosphate (Treat. 1) presented results in accordance to the field texture. III. Calcareous with soluble salts: Sodium hydroxide (Treat. 2) was again the best. Sodium hexametaphosphate (Treat. 3 and 4) was also effective. IV. Saline soils. a) Low content soluble salts: Sodium hydroxide and hexametaphosphate may be used without pre-treatment. b) High content of soluble salts: Hexametaphosphate (Treat. 3 and 4) is preferible. In this case sodium hydroxide cannot be used

Agroforestry system combining P. juliflora and buffel grass in the brazilian semi-arid region: preliminary results.

The exploitation of the plant resources in the Brazilian semi-arid region boils down to extracting timber for farming use and for commercial purposes, as well as to using native fodder species for feeding livestock. This exploitation is perfomed without any management criteria, thus briging about degradation of the plant cover. Cattle farming, predominant in the region, shows low productivity as a result mainly of the scant fodder avalilabel during the dry season. During this period, the pastures cultivated with grasses, mainly buffel grass (Cenchrus ciliaris L.) frequently do not offer a protein level sufficient for the animals to maintain or gain weight. Prosopis juliflora (Sw) DC is grown in the region as a fodder tree and for afforestation. The advantages this xerophyte offers for afforestation are its precociousness, drought hardiness, good-quality wooe for a variety of end uses, production of highly palatable and nutritive pods, and bearing of fruit during the dry season. The use of this leguminous tree in afforestation for timber and fodder production purposes throuth silvopastoral systems constitutes an economically and socially important alternative for the region. The purpose of this research was to study the technical viability of a silvopastoral system combining P. juliflora and C. ciliaris cv. Grayndah

Use of bovine digesta as organic fertilizer

Objetivou-se discutir o uso da digesta bovina como fonte de matéria orgânica para a agricultura. Atualmente existe uma preocupação crescente em relação à dilapidação dos recursos naturais, da deposição desenfreada de dejetos no meio ambiente. Iniciativas que reduzam os prejuízos no meio ambiente são importantes e necessárias, além de valorizar os produtos e melhorar o bem-estar social e ambiental. Resíduos da agroindústria podem ter um destino nobre, já que possuem características orgânicas que proporcionam a sua utilização como fertilizante orgânico no cultivo de plantas. A digesta bovina demonstra ser adubo orgânico promissor para agricultura, que promove o incremento de matéria seca, melhora o crescimento e o desenvolvimento das plantas, além de proporcionar benefícios ao meio ambiente

Safe Cultivation of Medicago sativa in Metal-Polluted Soils from Semi-Arid Regions Assisted by Heatand Metallo-Resistant PGPR

Soil contamination with heavy metals is a constraint for plant establishment and development for which phytoremediation may be a solution, since rhizobacteria may alleviate plant stress under these conditions. A greenhouse experiment was conducted to elucidate the effect of toxic metals on growth, the activities of ROS (reactive oxygen species)-scavenging enzymes, and gene expression of Medicago sativa grown under different metal and/or inoculation treatments. The results showed that, besides reducing biomass, heavy metals negatively affected physiological parameters such as chlorophyll fluorescence and gas exchange, while increasing ROS-scavenging enzyme activities. Inoculation of M. sativa with a bacterial consortium of heat- and metallo-resistant bacteria alleviated metal stress, as deduced from the improvement of growth, lower levels of antioxidant enzymes, and increased physiological parameters. The bacteria were able to effectively colonize and form biofilms onto the roots of plants cultivated in the presence of metals, as observed by scanning electron microscopy. Results also evidenced the important role of glutathione reductase (GR), phytochelatin synthase (PCS), and metal transporter NRAMP1 genes as pathways for metal stress management, whereas the gene coding for cytochrome P450 (CP450) seemed to be regulated by the presence of the bacteria. These outcomes showed that the interaction of metal-resistant rhizobacteria/legumes can be used as an instrument to remediate metal-contaminated soils, while cultivation of inoculated legumes on these soils is still safe for animal grazing, since inoculation with bacteria diminished the concentrations of heavy metals accumulated in the aboveground parts of the plants to below toxic levelsMarruecos. Centre National pour la Recherche Scientifique et Technique (CNRST)-España, Ministerio de Economía y Competitividad (MINECO)-PPR2 /2016/42Unión Europea (FEDER)-CGL2016-75550-

Enhancing the contribution of the legumes to the Nfertility of soils of the semi-arid zone of Nigeria

This paper attempts to focus attention on the N-fertility status of soils of the semi-arid zone of Nigeria. This is because, the region harbours a significant proportion of the national population figure, 75% of which is engaged in crop farming and animal keeping. These economic activities depend heavily on the soil resources available in the region. The first section, therefore, is a concise review of the general fertility status of the soils found in the region. This is followed by a section covering the position of legumes in the farming systems practiced by the semi-arid farmer. The role of the legumes as potential contributors to the N-economy of soils of the semi-arid zone is then highlighted. The need to develop appropriate technologies towards enhancing the contribution of legumes to the N-economy of the semiarid soils is also advocated. The paper concludes with a call on microbial physiologists,  geneticists and ecologists in concert with soil and plant scientists to rise to the challenge.Key words. Legumes, Rhizobium, seed inoculants, N-economy

Characterisation and classification of arecanut-growing soils of Karnataka

The present investigation was carried out to characterise the soils of areca based cropping system considering soil type and agro-climatic variability. Ten typical soil profiles were studied representing five different agro-climatic zones (ACZs) of Karnataka, namely, Tumkur and Hesarghatta (Eastern Dry Zone), T. Narasipura and Maddur (Southern Dry Zone), H D Kote and Hassan (Southern Transition zone), Mudigere and Sirsi (Hilly Zone), and Belthangady and Kumata (Coastal Zone). These pedons were studied for their morphological characteristics, physical and physicochemical properties. The arecanut-growing soils of Karnataka are generally deep to very deep, non-gravelly and well-drained soils. Texture ranged from sandy clay loam to clay in sub-surface. Soils of coastal and hilly zones were strongly acidic and had high organic carbon. In contrast, other sites of the southern transition zone to southern and eastern dry zone soils were near neutral to moderately alkaline with medium to high organic carbon content. Cation exchange capacity (CEC) ranged 2.5 to 32.6 cmol (p+) kg-1 base saturation varied 21.9 to 99.6 per cent. The major taxa of the soils identified at sub-group level of soil taxonomy were Rhodic Kanhaplustalfs, Typic Haplustalfs, Rhodic Paleustalfs, Typic Rhodustalfs, Vertic Haplustepts, Typic Haplustepts, Ustic Kanhaplohumults, Kanhaplic Haplustults and Typic Paleustults

Simulating the dynamics of soil organic matter in long-term rotation plots of Saskatchewan and Alberta

Non-Peer ReviewedThis study used the Century soil organic matter (SOM) model to simulate the dynamics in soil organic carbon, nitrogen, and phosphorus in long-term crop rotation studies established in Saskatchewan and Alberta. Observed losses of organic C, N, and P in the top 30 cm of a Brown Chernozem under fallow-wheat (FW) were 8.2, 1.7, and 1.0 g m-1 y-1. Soil erosion was responsible for 47% of the organic-N losses. The Century model closely mimicked the direction and magnitude of SOM change, within 10% of measured values. Similar SOM declining trends were observed in a thin Black Chernozem under FW and continuous wheat (CW), although soil erosion losses were higher than in the Brown Chernozem. Soil organic matter increased in the Brown Chernozem under CW and in the Black Chernozem under zero-tillage. Under no-till, the organic C, N, and P accumulated at an average rate of 101.7, 5.3, and 2.0 g m-2 y-1. In comparison, the Century model predicted a depletion of organic-C and N in the Brown Chernozem under CW and of organic-C under no-till. Model sensitivity analyses indicated that the rate of erosion and the fixed rate of organic matter decomposition had greater effects than plant biomass production on soil organic matter levels. Under aggrading SOM conditions, the Century model predicted organic carbon accumulation only after the respiration rate for the slow organic matter fraction was reduced by 50%

Phosphorus Sorption Characteristics of Red Soils from Lampung, West- and Central Java

Phosphorus Sorption Characteristics of Red Soils from Lampung, West- and Central Java (S.A. Siradz and R.J. Gilkes): Red soil is a common name used to identify any soil showing yellowish to reddish colour, these soils mainly occur in tropical and subtropical regions. The term is frequently used to convey an image of  red, infertile, acid soils in the tropics and is associated with tropical and subtropical climates which are characterized by high temperature and humidity. Major soil constraints to crop production may include low pH, low available P and high P fixation capacity, toxicity due to Al and  sometimes Mn and Fe, deficiencies of N, Ca, Mg, K,  and micronutrients e.g. Mo, Zn and Cu, low CEC and low base saturation, and very low content of weatherable minerals.  The aim of this study was to determine the phosphorus sorption characteristics of red soils from Lampung, West Java and Central Java. Soils were sampled at depth of 0-20 cm from minimally disturbed sites after discarding the uppermost few cm consisting of an accumulation of litter. The samples were air-dried, crushed using a ceramic mortar and pestle and then passed through a 0.5 mm stainless steel sieve. Measurements of P sorption were conducted by equilibrating 200 mg of air dry soil ( West Java and Central Java. Values of pH(NaF), Ald, and exchangeable Ca were most predictive of P sorption in these soils

Comparison between Walkley- Black and Loss- on- Ignition methods for organic carbon estimation in soil from different locations

      The present study aims to find out the best method for soil carbon determination using two methods, the wet acidified dichromate oxidation, Walkley-Black (W.B) and loss on ignition (LOI) methods. This study was employed on 30 soil samples from 0-20cm depth from three Duhok, Irbil and Sulaimaniya of Kurdistan region-Iraq. The following parameters are analyzed: organic C and the particle size distribution of the soil samples. The results of LOI and W.B methods were statistically analyzed by simple linear regression equations to interpret their relationship. The highest values of soil organic carbon (SOC) were found at Loss on ignition method ranged between 4.19 - 29.70 g kg-1 soil, whereas W-B method had the lowest values ranged between 3.0 – 19.0 g kg-1 soil for overall sites. There was a strong relationship between these two methods, so the amount of SOC using both methods had significantly a very strong correlation (R2=0. 93, p < 0.001), (R2=0. 87, p < 0.0001), (R2=0. 75, p < 0.001) in Sulaimaniya, Duhok and Irbil respectively. This study also revealed that silty clay and clay soils gave the highest values of the SOC by the two methods compared to the loamy soil. However, the soils that have more clay and carbonate contents gave higher values of SOC at high temperature using L.O.I technique. The results of this study revealed that both methods were reliable but W.B method was more accurate and suitable for soils with high clay contents and for the calcareous soils. Also, LOI is an accurate, if the fine fraction is present in low percentage. 

The impact of climatic variability over the period 1961- 1990 on the soil water balance of upland soils in the North East Arid Zone of Nigeria

Over the period 1961 – 90 the North East Arid Zone of Nigeria experienced a decline in annual rainfall totals and increased aridity which placed increasing pressure on rain fed, millet-based farming systems. The changes in seasonal rainfall total and distribution have been examined and it has been shown that the rate of decline has been consistent across the region. The decline has been dominated by reduction in the number of rain days during the middle of the rainy season and there is no evidence of a significant change in the length of the growing season. Over the same time period, there has been a small, but significant, increase in mean air temperature which has resulted in a small increase in potential evapotranspiration. Other climatic parameters (vapour pressure, solar radiation and wind speed) appear to have remained stable, although the paucity and dubious quality of much of the historical meteorological data make rigorous statistical analysis difficult. A water balance model (BALANCE) developed by the author, was calibrated for a millet crop grown on a typical sandy loam soil in Maiduguri (Nigeria). The model was necessarily parsimonious, but was shown to perform well when calibrated against observed soil water content. However, the empirical nature and high sensitivity of key parameters relating to bare soil evaporation and drainage mean that it is difficult to parameterise the model by laboratory, or independent field measurements. Applying the calibrated model to daily rainfall and average evapotranspiration data from Nguru (Nigeria) for the period 1961 – 93 showed that, with the exception of extreme drought years, the increased aridity would have had little impact on the viability of traditional millet and millet-cowpea intercropping systems prior to the early 1980s. However, after that date, predicted seasonal millet transpiration, and hence predicted yields, have declined, and long duration cowpea intercrops, which were traditionally matured on residual soil moisture after the millet harvest have had insufficient water. Whilst the BALANCE model has been useful in examining the impact of climatic variability on agro-hydrology, it is not a crop physiological model and the interaction between soil water and crop development is poorly represented. The model cannot, therefore be applied with confidence to investigate the potential yield benefits of physical or agronomic interventions to alleviate the impacts of aridity. Although more complex models exist to do this, they require detailed parameterisation of the crop physiology, which was not possible within the scope of this study