Acidic Clay Soil Research Articles

Olive Tree Physiology and Productivity Responses under No-Tillage or Digestate Amendment in an Acid Clay Soil

In Mediterranean countries characterized by increasingly extended hot and dry periods, olive trees are often conventionally practiced in low fertility and rainfed soils. This study investigated over a 15-month period how conventional tillage, combined with or without incorporated solid digestate, and no tillage affected selected soil properties, photosynthetic activity and productivity of mature olive trees growing in highly clayey acid soil with an unbalanced nutrient content and Mn excess. Neither in soil nor in drupes were Mn, Fe, Cu and Al contents affected by the managements. However, in soil, exchangeable Mn that was always larger than 200 mg kg−1 threshold and unbalanced Ca, Mg, and K contents were evidenced in all treatments. Non-tilled soil showed the highest (p < 0.05) stomatal conductance and photosynthetic rate, and the highest (p < 0.05) fruits and oil yields. Instead, conventional tillage negatively (p < 0.05) affected plant physiology and productivity, likely due to the tilled increase in aeration, enhancing soil water loss and organic C mineralization. Conversely, digestate addition increased TOC, TN and EC. Stomatal conductance, the photosynthetic rate and plant yield significantly recovered (albeit not to no-tillage values) in tillage combined with incorporated digestate, suggesting that digestate-derived organic matter created soil conditions less constraining to plant growth and productivity than the conventional tillage did. Dealing with soil properties and climatic conditions is the key for adopting the best management practice for preserving plant productivity and soil fertility.

ВИРОЩУВАННЯ СОРГО ЗЕРНОВОГО НА КИСЛИХ ГРУНТАХ В УМОВАХ ЗАКАРПАТСЬКОЇ ОБЛАСТІ

The work aims to conduct production field research to determine the potential yield level of grain sorghum on acidic soils, as well as work out the generally accepted basic elements of cultivation technology with its subsequent cultivation in the Zakarpattia region. Materials and methods. In 2023, the production range for growing grain sorghum at Karpatiagroproduct LLC was located in the lowland zone of Uzhgorod district, Zakarpattia region. The article describes agrotechnical operations related to soil cultivation, application of fertilizers and plant protection products that were used in the farm, the main of which was the application of mineral fertilizer diammonium phosphate (NP 18:46) at the rate of 160 kg during sowing. The sowing rate was 165,000 seeds per hectare with a row width of 37 sm. Results. Sorghum is not picky about soils, so it can grow on both clay and sandy soils. The landfill where sorghum was grown is characterized by a low content of mobile phosphorus (6.33 mg/kg), a very low content of total nitrogen (N-NO3- + N-NH4+ – 8.92 mg/kg). According to the degree of acidity, the soil belongs to a very acidic soil (the hydrogen index of the saline extract of the soil is 4.08). In the economic conditions of 2023, the yield of sorghum grain hybrid Iceberg was 4.4 t/ha, which is 1.0 t/ha more than the average yield of sorghum in Ukraine over the past 10 years. Taking into account the genetic potential of this crop and the sufficient level of moisture supply of the territory, the level of the sorghum harvest should be twice as large. Because sorghum is not recommended to be grown on acidic, waterlogged soils with a close occurrence of groundwater, the underachieved level of the harvest to some extent may be related to this. In addition, the low content of mobile phosphorus and very low content of available nitrogen, which is characteristic of acidic clay soils, to some extent negatively affected the processes of crop yield formation. Conclusions. The obtained sorghum yield at Karpatiagroproduct LLC - 4.4 t/ha is lower than the average yield in Italy, by 2.6 t/ha, and in France - by 0.6 t/ha. However, it was in the territory of Ukraine that the record yield of sorghum in the world was obtained - 14.43 t/ha, which testifies to the high potential of grain sorghum and the unlimited potential of scientific and industrial research to reveal the genetic expression of this crop. Keywords: grain sorghum, yield, soil pH, «Iceberg» hybrid, agricultural technology.

Enhancing NPK Uptake and Biomass of Blueberries in Alluvial Clay Soil Using Biochar and Compost

Background: The Mekong Delta features acidic clay soil of alluvial origin with a soil texture ranging from silty clay to clay. The growth of wild blueberry plants in clay soils requires the addition of materials to enhance soil porosity and aeration. Objective: The objective of this study was to examine the effects of the combined use of biochar and compost on the growth, yield, and NPK uptake of blueberry ( Vaccinium tenellum) cultivated in the Mekong Delta. Methods: The pot experiment had a 3 × 3 factorial design, containing the application of biochar at 0, 10, and 20 t ha -1 (B0, B10, and B20, respectively), compost at 0, 5, and 10 t ha -1 (C0, C5, and C10, respectively), and NPK at 45:20:20 kgha -1 according to the growth stages of blueberries. Results: The interaction between biochar and compost provided a more efficient response in terms of plant growth, yield, and NPK uptake. Notably, in the combined application of B20 and C10, NPK uptake and biomass of blueberries were significantly increased. However, only the concentration (gkg -1) of N (14.8) and K (3.82), except for P (1.37), in the blueberry leaves were below the Trevett threshold. Conclusion: This approach effectively mitigates the challenges posed by high clay content in the soil, which results in poorer soil porosity and aeration. The findings emphasize the potential benefits of tailored soil amendment strategies to optimize blueberry cultivation in similar environments.

Does micro/nano biochar always good to phytoremediation? A case study from multiple metals contaminated acidic soil using Salix jiangsuensis '172'

Biochar amendments have shown great superiority in reduction of heavy metals (HM) toxicity and soil amelioration in severely contaminated mining areas, which suggested to facilitate vegetation rehabilitation using fast-growing trees. Bone biochar (BC) and ball-milled bone biochar (MBC) were fabricated by pyrolyzing bone meal at 600°C followed by eco-friendly wet-milling techniques. The effect of BC and MBC application (0, 0.5, 1.0, 2.0 and 4.0 wt%) on soil properties, plant growth and metal accumulation of Salix jiangsuensis '172' (SJ-172) in multi-metal (Cu, Pb, Cd and Mn)-contaminated acid clay soil was investigated in a 150-day pot experiment. The results showed that BC and MBC considerably improved the survival rate of SJ-172 when the application rate was larger than 1.0%. MBC displayed outstanding performance in reducing HMs bioavailability and improving N and P soil fertility, while BC enhanced the reduction in acidity and increase in K supply. Interestingly, BC enhanced HMs accumulation (Cd 115.23%, Pb 161.82%, Mn 285.23% and 219.29% Cu at 4% application rate) by SJ-172 compared with MBC. Taken together, the good performance of BC in enhancing HMs accumulation in SJ-172 indicated that it is a promising amendment for phytoremediation of clay soils, while MBC can be utilized as an excellent amendment for HMs stabilization.Graphical

Soil microbial community dynamics after co-application of biochar and paper mill biosolids

Co-applying biochar and paper mill biosolids (PB) improves the potential of these by-products as soil amendments. Assessing the response of soil microbial communities to the co-application of biochar and PB is of great importance to further understanding their effectiveness. This hypothesis was tested in a 112-day incubation study performed separately on two acidic soils (Kamouraska clay and St-Antoine sandy loam) using two PB types (PB1 with C/N = 24 and PB2 with C/N = 13), co-applied with one of three rates (0%, 2.5%, and 5% w/w) of pine (Pinus strobus L.) biochar. An unamended control and a mineral-fertilized treatment were used as a reference. In the Kamouraska clay soil, co-applying 5% biochar and any PB increased microbial activity compared to PB-only application, as indicated by the fluorescein diacetate (FDA) hydrolysis assay. In both soils, co-applying biochar and PB did not affect microbial diversity and community structure compared with PB only. The application of any PB, however, increased microbial activity in both soils, while only PB2 shifted microbial community structure. Within each amendment and in both soils, microbial activity was lower at day 112 than at days 28 and 56, while major temporal shifts were observed only for bacterial community structure. Indeed, the difference in bacterial community structure between amendments was more pronounced at day 112. This study suggests that co-applying biochar and PB can improve soil properties than application of PB alone by increasing soil microbial activity without side effects on microbial diversity and community structure, especially in acidic clay soils.

Effect of Long-Term Integrated Nutrient Management (INM) Practices on Soil Nutrients Availability and Enzymatic Activity under Acidic Inceptisol of North-Eastern Region of India

ABSTRACT Soil acidity is one of the main limitations for optimal use of land resources for better crop production. And, long-term fertilization experiments found to be helpful in increasing the nutrient supply in these acidic soils. Keeping this in view, a field experiment on rice was carried out by applying biofertilizers and enriched compost in an acidic Inceptisol of Assam over 10 successive years (2006–15) to examine its effects on nutrient availability and soil enzymatic activity. This experiment had five treatments viz. absolute control (T1), 100% recommended doses (RD) of inorganic NPK (T2), 50% RD of inorganic NP + 100% K +biofertilizers (T3), 50% RD of inorganic NP + 100% K +1 tonne enriched compost ha−1 (T4) and 25% RD of inorganic NP + 100% K +2 tonnes enriched compost ha−1 (T5) under randomized block design with four replications. After completing 10 years of experiment, it was observed that integrated use of enriched compost and biofertilizers with reduced doses of inorganic fertilizers enhanced the soil enzymatic activity as well as nutrient availability in rice grown in acidic clay loam soils of Assam. Application of biofertilizers and enriched compost had positive impact on plant accessible nitrogen, phosphorus and potassium in soil as compared to inorganic fertilizers. Also soil organic matter content increased considerably by these treatment. Integrated nutrient management practice in rice had also significantly enhanced the dehydrogenase, fluorescein diacetate and phospho-monoesterase activity in soil.

Correlations among soils’ features, forest plant species, and vegetable crops in Tokpli mining zone (South Togo)

ABSTRACT Agriculture and forestry resources are central to African development. In this study, Tokpli mining zone (Togo) soils were characterised and the ones appropriate to garden crops and reforested species identified and located on a map using several database and literature. Results showed that tomato (Solanum Lycopersicum) and chilli pepper (Capsicum annuum) are suitable for slightly acidic clay soils of Ahlimegni. Abelmoschus esculentus is suitable for Assou-kondji soil. Solanum macrocarpon was found appropriate to Ziome-kondji and Anagonou-kpota soils. Forest species such as Salix babylonica, Khaya senegalensis, Eucalyptus spp., and Terminalia superba exhibited best growth on slightly acidic clay soils of Ahlimegni area, rich in organic matter. Acacia auriculiformis, Azadirachta indica, Cola gigantea, and Albizia zigya can grow better on the slightly basic sandy soils of Anagonou-kpota and Ziome-kondji. Other species like Gmelina arborea, Mangifera indica, Salix babylonica, and Morinda lucida were found not selective and could be reforested on all soil types.

Indirect DNA extraction method suitable for acidic soil with high clay content

DNA extraction is an essential procedure when investigating microbial communities in environmental samples by sequencing technologies. High clay soils can be problematic as DNA adsorbs to the clay particles and can thereby be preserved from lysed, non-viable cells for a substantial period of time. In order to accurately estimate the intact and living microbial community in the soil, extracellular DNA from dead, remnant bacterial cells needs to be removed prior to DNA extraction. One possibility is to use a sodium phosphate buffer to release both extracellular DNA and bacterial cells from the clay particles. After removing the extracellular DNA by centrifugation, the remaining viable cells can be harvested and DNA extracted. The described method is a modification of a procedure for separating extracellular DNA and bacterial cells from acidic clay soils.•The modified method increases bacterial cell yields from acidic clay soils, such as acid sulfate soil.•The modified method eliminates some steps from the original method, as only DNA from intact bacterial cells is required.•The indirect DNA extraction method increases the workload compared to standard direct extraction methods, but subsequent downstream analyses will give a more representative picture of the viable microbial community composition in the soil.

Phytoremediation Efficacy of Salix discolor and S. eriocephela on Adjacent Acidic Clay and Shale Overburden on a Former Mine Site: Growth, Soil, and Foliage Traits

Plants regularly experience suboptimal environments, but this can be particularly acute on highly-disturbed mine sites. Two North American willows—Salix discolor Muhl. (DIS) and S. eriocephala Michx. (ERI)—were established in common-garden field tests on two adjacent coal mine spoil sites: one with high clay content, the other with shale overburden. The high clay content site had 44% less productivity, a pH of 3.6, 42% clay content, high water holding capacity at saturation (64%), and high soil electrical conductivity (EC) of 3.9 mS cm−1. The adjacent shale overburden site had a pH of 6.8, and after removing 56.5% stone content, a high sand content (67.2%), low water holding capacity at saturation (23%), and an EC of 0.9 mS cm−1. The acidic clay soil had significantly greater Na (20×), Ca (2×), Mg (4.4×), S (10×), C (12×) and N (2×) than the shale overburden. Foliar concentrations from the acidic clay site had significantly greater Mg (1.5×), Mn (3.3×), Fe (5.6×), Al (4.6×), and S (2×) than the shale overburden, indicating that these elements are more soluble under acidic conditions. There was no overall species difference in growth; however, survival was greater for ERI than DIS on both sites, thus overall biomass yield was greater for ERI than DIS. Foliar concentrations of ERI were significantly greater than those of DIS for N (1.3×), Ca (1.5×), Mg (1.2×), Fe (2×), Al (1.5×), and S (1.5×). There were no significant negative relationships between metal concentrations and growth or biomass yield. Both willows showed large variation among genotypes within each species in foliar concentrations, and some clones of DIS and ERI had up to 16× the Fe and Al uptake on the acidic site versus the adjacent overburden. Genetic selection among species and genotypes may be useful for reclamation activities aimed at reducing specific metal concentrations on abandoned mine sites. Results show that, despite having a greater water holding capacity, the greater acidity of the clay site resulted in greater metal mobility—in particular Na—and thus a greater EC. It appears that the decline in productivity was not due to toxicity effects from the increased mobility of metals, but rather to low pH and moisture stress from very high soil Na/EC.

Non-stereoselective transformation of the chiral insecticide cycloxaprid in aerobic soil.

Cycloxaprid (CYC) is one of the most effective neonicotinoid insecticides and is proposed to be a replacement of imidacloprid that has caused concerns over non-targeted resistance and ecological toxicity worldwide. The present study was performed with the 14C-labeled racemic CYC and its two enantiomers in aerobic soil. Racemic CYC and the enantiomers 1S2R-CYC and 1R2S-CYC underwent non-stereoselective degradation in the three soils tested. During the incubation period, CYC was transformed into three achiral degradation products which displayed varying degradation kinetics dependent upon soil properties. The soil properties were found to significantly influence the CYC metabolite profiles. The fastest degradation occurred in loamy soil, whereas the slowest reactions occurred in acidic clay soil. The primary transformation of CYC included cleavage of the oxabridged seven-member ring and CN between chloropyridinylmethyl and imidazalidine ring, carboxylation of the alkene group, and hydroxylation of imidazolidine ring. The results shed light on understanding of CYC degradation and provided useful information for applications and environmental assessments of chiral pesticides.

Lithic Residue Survival and Characterisation at Star Carr: a burial experiment

A modern burial experiment was devised to test microscopic residue survival in acidic peat and slightly acidic clay soils at the Early Mesolithic site of Star Carr (North Yorkshire, UK), and at nearby control location. The experiment addresses concerns regarding the applicability of residue analysis in varied burial environments, and particularly in highly acidic archaeological conditions. Flint flakes (n= 78, including blank controls) were used on twelve plant, animal, and mineral materials to create residues and then buried. The residues were examined 1 month and 11 months after burial. An unburied reference collection containing the same twelve residue types in a fresh state was compared to the buried residues to assess diagenesis. The residue types that survived across all burial conditions and time intervals were: softwood tissue, tree resin, bird feathers, squirrel hair, and red ochre. During microscopic analysis, it became clear that many residues lack diagnostic traits, and thus an assessment of the extent to which each residue can be identified was conducted. The degree to which residues were able to be identified was further investigated with a variable pressure scanning electron microscope (SEM). SEM images of the reference residues were compared to the reflected VLM micrographs of the same residues, which improved characterisation in some cases. Residues were grouped into three categories (diagnostic, distinctive, and non-distinctive) within a visual characterisation guide. Our in situ microscopic analyses indicated that few residue types have diagnostic traits that allow them to be identified unambiguously, and thus further characterisation techniques are often required.

Effects of Wood Ash on the Chemical Properties of Soil and Crop Vitality in Small Plot Experiments/ Fahamu hatása a talaj kémiai jellemzőire és a termény vitalitására egy kisparcellás kísérletben

Abstract Wood-burning power plants and heating plants produce a great amount of wood ash as a by-product of the combustion process. In 2009 we launched an experiment in which we examined the composition of ash, the nutrient supplying capacity of soil mixed with ash, and the availability of its constituents. In the spring of 2010, we conducted small plot experiments using wood ash applications equivalent to 0; 1; 2.5; 5 and 10 t of wood ash/ha, on slightly acidic clay loam soil using white mustard and rye grass as the test plants. The pH value of the soil rose in a statistically verifiable way as a result of the ash treatments. After the application of ash, the P2O5 and K2O-content of the soil rose significantly; the treatments also increased the magnesium and sulphur content of the arable soil as well as the level of Zinc among the microelements. However, none of the wood ash applications caused verifiable changes in the number of shoots, in the green mass, or in the height of test plants. The increased nutrient supply of the soil through the treatments was not reflected in the nutrient content of the plants during the first year.

Nitrogen fixation of Acacia mangium Willd. from two seed sources grown at different levels of phosphorus in an Ultisol, South Sumatra, Indonesia

Phosphorus (P) is required to facilitate the fixation of atmospheric nitrogen (N) by leguminous species such as Acacia mangium. We studied the N fixation of A. mangium trees grown from two seed sources. These consisted of bulk seedlots collected from seed orchards in Sumatra, one based on natural provenances from the Cairns region, Queensland, Australia, and the other on the Muting natural provenance, Papua, Indonesia. The seedlots were grown under contrasting P supply (application rates of 0 and 100 kg ha−1) on acidic clay soils in a field experiment at Lematang, South Sumatra. The 15N natural abundance method was used, with Eucalyptus pellita as a non-N-fixing reference species. Foliage samples were collected at age 12 and 18 months. Application of P increased stem volume, foliage N concentrations and the amount of N fixed in both seed sources at 12 and 18 months of age. For the Cairns-origin seed source, the percentage of N derived from atmospheric N was low (c. 14%) without P addition, but increased by more than four-fold with P addition. In contrast, N fixed by the Muting-origin seed source (c. 45–60%) was not significantly affected by P addition. The Cairns-origin seed source partly compensated for lower N fixation by taking up a larger amount of soil N. Thus there were significant differences between seed sources in their N-fixing capacity and the effect of P nutrition on this process. The higher productivity of Muting under low P application appeared to be associated with better P utilisation and greater N fixation, but it was still responsive to P application.

Seasonal and inter-annual variation of leaching of dissolved organic carbon and nitrogen under long-term manure application in an acidic clay soil in subtropical China

Dissolved organic matter (DOM) plays an important role in soil biological activity and transport of pollutants and nutrients in soils, but very little information is available with regard to the long-term impact of agricultural management practices on the dynamics and fate of DOM in acidic soils. The seasonal and inter-annual variation of dissolved organic carbon (DOC) and nitrogen (DON) contents and leaching were investigated in an acidic clay soil (Ferric Acrisol) by a long-term field lysimeter experiment in subtropical China. The experiment was conducted from 2002 to 2010 with 4 fertilization treatments under maize monoculture: no manure (CK), low-rate manure with 150kgNha−1y−1 (LM), high-rate manure with 600kgNha−1y−1 (HM), and high-rate manure with 600kgNha−1y−1 and lime at 3000kg Ca(OH)2ha−13y−1 (HML). Manure application resulted in a seasonal variation of soil DOC and DON, and significant effects were observed by manure DOC, microbial biomass and soil water content. Soil DOC, which was mainly determined by soil organic matter and soil water content, increased yearly until the seventh year when it was stabilized. Manure application on acidic clay soil did not alter DOC leaching, whereas DON leaching clearly increased after three years of high manure application of 600kgNha–1y–1. The average annual DON leaching losses under long-term manure application had a range of 3.8–5.4kgha–1, accounting for 6–11% of total nitrogen leached. The addition of lime, combined with manure application, produced no impact on soil dynamics and leaching of DOC and DON, with the exception of increasing emission of CO2.

Coppice growth responses of two North American willows in acidic clay soils on coal mine overburden

Mosseler, A. and Major, J. E. 2014. Coppice growth responses of two North American willows in acidic clay soils on coal mine overburden. Can. J. Plant Sci. 94: 1269–1279. Acid-generating mine spoils with low pH are a major problem for revegetation and site reclamation. We compared growth responses of 15 genotypes from two widespread willow species, Salix discolor Muhl. (DIS) and S. eriocephala Michx. (ERI), native to eastern and central North America on two adjacent coal mine spoil sites that differed strongly in both pH (3.6 vs. 6.8) and soil texture. Despite significantly poorer growth responses for several coppice biomass traits on a highly acidic clay deposit compared with adjacent shale overburden, these willow clones demonstrated a surprising tolerance for extremely acidic soil conditions. Analysis of survival and growth uncovered genotype×environment interactions, indicating that both species and genotypic differences within species could be used to select better-adapted genotypes for extreme conditions. Most ERI and DIS clones grew comparatively better on the shale overburden site, but two of eight ERI clones and one of seven DIS clones grew significantly better on the acidic clay site, indicating the possibility for clonal selection for specific site adaptations within a species. Allometric relationships between coppice height and basal stem diameter were constant at both the species and site levels. However, there was a divergence of height and diameter in their relationship with green mass yields on the two different site types.

Diastereoselective Metabolism of a Novel Cis-Nitromethylene Neonicotinoid Paichongding in Aerobic Soils

Many pesticides are chiral but used as racemic mixtures, even though their stereoisomers are often degraded stereoselectively in soils. Evaluation of degradation of chiral compounds is mostly focused on the enantioselectivity rather than diastereoselectivity/epimer preferences. In this study, we explored the diastereoselective transformation of paichongding (IPP), a novel chiral neonicotinoid with broad-spectrum insecticidal activity, to several degradation intermediates in different soils. (14)C-Labeling coupled with LC-MS/MS and high resolution MS were used to track residues of IPP and identify major transformation metabolites. The stereoisomers of IPP known as 5R, 7R-IPP (RR-IPP), 5S, 7S-IPP (SS-IPP), 5S, 7R-IPP (SR-IPP), and 5R, 7S-IPP (RS-IPP) showed diastereoselective/epimer-selective persistence in all soils except an acidic clay soil. Moreover, IPP was transformed to a range of degradation intermediates (M1-M6), which also showed significant diastereoselective and soil preferential formation. Depropylation, nitrosylation, denitration, demethylation, dehydroxylation, and ketonization contributed to IPP transformation. The diastereoselective degradation of the parent compound and formation of incomplete intermediates implies that diastereomers/epimers should be regarded as different chemicals. The approach of coupling (14)C and MS may be used as an effective tool to understand the environmental processes and risks of other man-made chiral compounds.

PRODUCTIVIDAD DEL LIMÓN ‘PERSA’ INJERTADO EN CUATRO PORTAINJERTOS EN UNA HUERTA COMERCIAL DE VERACRUZ, MÉXICO

There were 36,166.36 ha planted with ‘Tahiti’ lime (Citrus latifolia Tan.) in Veracruz, Mexico in 2010, which produced 437,460.80 tons of fruit valued at 88.07 million dollars. Because rootstocks influence vegetative growth, citrus fruit yield and quality, depending on the species of rootstock, soil type and climate where they are cultivated, we compared the agronomic performance of 11-year-old ‘Tahiti’ lime trees grafted onto Carrizo citrange, Swingle citrumelo and Volkamerian and Rough lemons, planted with 4 x 6 m spacing, in a thin, strongly acidic (pH 4.5) clay soil. Tree dimensions, yield, production efficiency and fruit quality of eight harvests, from June 2008 to July 2009, were recorded. The most important results were: Carrizo, Swingle and Volkamerian induced lower height and canopy volume than Rough lemon, but the canopy formation of ‘Tahiti’ lime was wider than high, with all of them, b) fruit yield per tree was higher with Rough, but its production efficiency equaled that obtained with Carrizo and Swingle, c) Carrizo, Rough and Swingle induced a higher volume of export- grade (United States) ‘Tahiti’ lime fruit, with no differences among them in terms of the commercial sizes of the fruit produced, and d) the agronomic performance of Carrizo and Swingle, in terms of vigor, tree size, production efficiency, fruit quality and tolerance to termites, offers greater advantages for growing ‘Tahiti’ lime in savanna soils.

Effect of Integrated Nutrient Management on Soil Physical Properties and Crop Productivity under a Maize (Zea mays)–Mustard (Brassica campestris) Cropping Sequence in Acidic Soils of Northeast India

A five-year (2001/02–2006/07) field experiment was carried out on acidic clay loam soil classified as Typic Hapludalf with a maize–mustard crop sequence to study the effect of continuous application of nitrogen, phosphorus, and potassium (NPK) fertilizers alone and in combination with lime, farmyard manure (FYM), and biofertilizers on soil physical properties, soil organic carbon (SOC), soil microbial biomass carbon (SMBC), and crop yields on the hilly ecosystem of Meghalaya. Significant improvement in the soil physical conditions of the soil was observed under integrated application of organic manure and inorganic fertilizers. Addition of NPK fertilizers along with organic manure, lime, and biofertilizers increased soil organic carbon (SOC) content, aggregate stability, moisture-retention capacity, and infiltration rate of the soil while reducing bulk density. The SOC content under the treatment of 100% NPK + lime + biofertilizer + FYM was significantly greater (68.58%) than in control plots. Maize and mustard crop yields also significantly increased (4.73- and 21.09-folds, respectively) with continuous application of balanced inorganic (100% NPK) + lime + biofertilizer + FYM as compared to the control plots. However, crop yields drastically reduced under application of integrated nutrients without FYM as compared to the treatment with FYM application. Thus, the results suggest that integrated use of a balanced inorganic fertilizer in combination with lime and organic manure sustains a soil physical environment that is better for achieving higher crop productivity under intensive cropping systems in the hilly ecosystem of northeastern India.

Atributos químicos, físico-hídricos e mineralogia da fração argila em solos do Baixo Amazonas: Serra de Parintins

Estudos sobre os atributos dos solos amazônicos geram informações para compor um levantamento atual sobre suas condições frente às várias formas de alterações que estão sujeitos. O objetivo deste trabalho foi descrever e avaliar a evolução química, físico-hídrica, bem como a mineralogia de Latossolos no Baixo Amazonas como forma de entender as variações desses atributos em diferentes coberturas vegetais. Coletaram-se amostras deformadas e indeformadas para análises físicas, químicas, mineralógicas e hídricas, em dois pontos de uma topossequência na Serra de Parintins: platô e vertente, sendo três perfis de solo em cada posição. Os resultados obtidos demonstraram que a floresta predominante sobre os perfis do topo e vertente promove condições físicas e hídricas adequadas para uma boa agregação, maior intensidade de poros grandes, maior condutividade hidráulica saturada (Ko) e melhor retenção hídrica dos solos. Fato semelhante ocorrendo com as áreas de capoeira, apresentando boa permeabilidade, porosidade e retenção de água no solo. O acúmulo de carbono é maior dos perfis da vertente, decrescendo em profundidade, relacionando-se diretamente com Ko e com o sistema radicular. A análise mineralógica da fração argila indicou a caulinita como argilomineral predominante, seguido pelos minerais gibbsita, goethita, quartzo e anatásio, não havendo variações ao longo da paisagem. A Serra de Parintins possui um solo pobre em nutrientes, ácido, com textura média a muito argilosa com acúmulo de plintita nos horizontes subsuperficiais, evitando o fenômeno de terras caídas. Um gradiente elevado de umidade volumétrica é observado nos horizontes subsuperficiais, havendo mais água retida, quando comparado com horizontes superficiais.

Field Performance and Nodulation of Yardlong Bean in the Humid Tropics

Yardlong bean [Vigna unguiculata (L.) Walp. subsp. sesquipedalis] is a popular vegetable grown throughout the tropical Far East, including Guam. There is little information on growth response of yardlong beans and nodulation by indigenous bradyrhizobia colonized in agricultural soil regimes of Guam. Five cultivars of yardlong bean were evaluated in a 2-year study for their field performance and nodulation with indigenous bradyrhizobia on a Pulantat clay soil (Barrigada), an Akina silty clay soil (Ija), and a Guam cobbly clay loam soil (Yigo) on Guam. The 1996 experiment was conducted during the dry season (12 Feb.–10 May) and the 1997 trial in wetter months (28 Apr.–25 July). The study indicated that season, location, and cultivar affected pod yield. The cv. Green Pod Kaohsiung grown in Barrigada during the dry season had the highest pod yield. ‘Local Selection’ was one of high yielders in all sites in both seasons. Nodulation was observed at all locations with the least number of nodules found at Yigo with a calcareous alkaline soil. ‘Local Selection’ had the most nodules at Ija with an acidic silty clay soil. There was no correlation between the number of nodules found in roots and pod yield. The study indicated that yield potential of yardlong bean would be improved by selection of planting season, location, and cultivar.