Exchangeable Magnesium Research Articles

Ammonium Chloride Solution as an Alternative Laboratory Procedure for Exchangeable Cations in Southern Brazilian Soils

Most Brazilian soil-testing laboratories use Mehlich 1 and 1.0 M potassium chloride (KCl) solutions as extractants for the determination of phosphorus (P), potassium (K), and sodium (Na) and for exchangeable calcium (Ca), magnesium (Mg), manganese (Mn), and aluminum (Al) in agricultural soil samples. Other laboratories use a combination of exchangeable ionic resin and KCl procedures. With recent adoption of the inductively coupled plasma (ICP-OES) in routine soil-testing laboratories, soil extraction with 1.0 M ammonium chloride (NH4Cl) became an alternative due to the possibility of determining all exchangeable elements in one run (Ca, Mg, K, Mn, Na, and Al), leaving determination of phosphorus (P) with Mehlich 1 or exchangeable ionic resin. To evaluate the performance of the NH4Cl solution, an experiment was carried out with thirty-seven samples of soils representative of the southernmost state of Brazil, Rio Grande do Sul. Four extraction solutions [Mehlich 1 at soil/solution ratio of 1:10 and 1.0 M ammonium acetate (NH4OAc), 1.0 M KCl, and 1.0 M NH4Cl at soil/solution ratio 1:20] were used with three different shaking times (5, 30, and 60 min). Correlation coefficients among all methods were high. Mehlich 1 did not perform well against NH4OAc and NH4Cl, despite the high correlation coefficients, with values consistently lower for K, even when the time of extraction was increased from 5 to 30 or 60 min. However, for concentrations less than 0.30 cmol kg−1 (i.e., in the range of K deficiency), both solutions performed similarly. Calcium and Mg increased with time of shaking. Comparable values of exchangeable Ca, Mg, and K, as well as of Al and Mn, were obtained with 1.0 M NH4Cl with 60 min shaking and the standard procedures of 1.0 M NH4OAc and 1.0 M KCl. The determination of Al by traditional titration/back-titration of the 1.0 M KCl solution gave slightly greater results compared to ICP-OES obtained using extraction with 1.0 M NH4Cl. The results indicate that for Ca, Mg, Mn, and Al, it is possible to replace the traditional 1.0 M KCl extraction with 1.0 M NH4Cl solution, with 60 min shaking time and a soil/solution ratio of 1:20.

Assessing Soil Nutrient Additions through Different Composting Techniques in Northern Ethiopia

The use of vermi-compost in northern Ethiopia is not a common practice. It is, therefore, important to understand the possible impediments through studying its chemical and biological properties and its extra contribution compared to other composting techniques. Four compost types (vermi-compost, conventional compost, farmers’ compost and community nursery compost) with three replications were used in this study. The farmers’ and community nursery compost samples were collected from different places in Tigray; whereas, the vermi- and conventional composts were prepared at Mekelle University following a standard composting procedure. Six major composting materials were identified in the visited sites from farmers’ and community nursery foremen’s interview. These composting materials were also used for the vermi- and conventional composting. Twelve composite compost samples were taken for analysis of macro- and micro-nutrients. The results of the experiment showed that for all treatments, despite of having high content of total C (5.04 – 10.67%), the C/N ratio (12.19 – 12.22) was low. This suggests that as the C/N ratio is lower than the threshold (< 30), mineralization is faster, nutrients eventually become available and a large amount of N is lost. Soil pH, exchangeable Magnesium (ex.Mg), exchangeable Potassium (ex.P), available Phosphorus (ava.P), and Cation Exchange Capacity (CEC) showed significant differences among the different composting techniques. Among the selected compost types, ex.Mg, ex.Ca and av.P were higher for vermi-compost. The lowest was recorded in community nursery compost. The use of vermi-compost is, therefore, very helpful in terms of providing beneficial soil nutrients as compared to other compost types.Keywords: Conventional compost, Vermi-compost, farmers’ compost, Nursery compost, Macro-nutrients, Micro-nutrients.

Effects of Continuous Use of Chemical Fertilizers and Manure on Soil Fertility and Productivity of Maize–Wheat under Rainfed Conditions of the Western Himalayas

Long-term effects of continuous use of chemical fertilizers and manure on soil fertility and productivity of a maize–wheat system were investigated in the ongoing long-term fertilizer experiment, during rabi (2007–2008) and kharif (2008) seasons at the research farm of Chaudhary Sarwan Kumar Himachal Pradesh Agricultural University–Hill Agricultural Research and Extension Centre, Dhaulakuan. After 16 cropping cycles, bulk density decreased in plots where farmyard manure (FYM) was applied, whereas pH decreased in all the treatments. The organic carbon content of the soil increased in all the treatments except 100% nitrogen (N). Cation exchange capacity (CEC) increased in all the treatments over the initial status of the soil. Available N showed buildup over the initial status in most of the treatments. Available phosphorus (P) declined from initial status in treatments where only N was applied alone or with FYM. There was reduction in available potassium (K) status in all the treatments except 100% NPK. Continuous addition of FYM with balanced application of inorganic fertilizers improved content of exchangeable calcium (Ca) and magnesium (Mg) over initial status compared to imbalanced application of fertilizers. Continuous use of imbalanced inorganic fertilizers resulted in lesser crop yields and nutrient uptake compared to that with the application of balanced dose of inorganic fertilizers with FYM.

The effect of soil on cork quality.

The present work aimed to contribute for a better knowledge regarding soil features as cork quality indicators for stoppers. Cork sampling was made in eight Cork oak stands (montados de sobreiro) located in the Plio-Plistocene sedimentary formations of Península de Setúbal in southern Tagus River region. The samples used to classify the cork as stopper for wine bottles were obtained in eight cork oak stands, covering soils of different types of sandstones of the Plio-plistocene. In each stand, we randomly chose five circular plots with 30 m radius and five trees per plot with same stripping conditions determined by: dendrometric features (HD- height stipping, PBH- perimeter at breaster height), trees vegetative condition (defoliation degree); stand features (density, percentage canopy cover); site conditions (soil type and orientation). In the center of each plot a pit was open to characterize the soil profile and to classify the soil. Cork quality for stoppers was evaluated according to porosity, pores/per cm2 and cork boards thickness. The soil was characterized according to morphological soil profile features (lithology, soil profound, and soil horizons) and chemical soil surface horizon features (organic matter, pH, macro, and micronutrients availability). Based on the variables studied and using the numerical taxonomy, we settled relationships between the cork quality and some soil features. The results indicate: (1) high correlation between the cork caliber and boron, cation exchange capacity, total nitrogen, exchange acidity, and exchangeable magnesium, potassium, calcium, and sodium in soils of theirs cork oaks; (2) the cork porosity is correlated with the number of pores/cm2 and magnesium soil content; (3) the other soil features have a lower correlation with the caliber, porosity, and the number of pores per cm2.

Cation Exchange and Mineral Reactions Observed in MX 80 Buffer Samples of the Prototype Repository In Situ Experiment in Äspö, Sweden

AbstractBentonites are candidate materials for high-level radioactive waste (HLRW) repositories and, therefore, are investigated with respect to long-term stability. In order to identify possible bentonite alteration processes, long-term in situ tests are conducted in rock laboratories. The prototype repository in situ experiment (PR) is one of the best examples of this kind of test due to the size of the installation as well as the duration. In the present study, chemical and mineralogical alteration processes of the bentonite MX 80 after an 8 y heating period were investigated. The water content of all samples increased following inflowing Na-Ca-Cl-type granitic groundwater causing cation exchange in the bentonite buffer materials. Exchangeable magnesium was desorbed in the buffer and MgO concentration increased at the bentonite-Cu canister interface; the Mg sink could not be detected, however. CaO also accumulated at this interface mainly as Ca carbonate and Ca sulfate. Cu corrosion products were identified at the bentonite-canister interface by chemical analysis, scanning electron microscopy equipped with energy dispersive X-ray spectroscopy (SEM-EDX), and differential thermal analysis. Up to 0.5 mm into the bentonites Cu could be detected by SEM-EDX. No cristobalite dissolution was observed in contrast to other in situ tests in which iron heaters were used. The corrosion products and the lubricant which was added during manufacturing of the bentonite blocks were mixed with the bentonite at the bentonite-canister interface. A quantitative measure of that mixture was the decrease in the cation exchange capacity (CEC). The CEC also reduced in all other samples, however, compared to the CECs of the reference samples, particularly in the warmer deposition hole 5 compared to the colder deposition hole 6. Overall, the PR in situ experiment proved that cation exchange reactions occurred in full-scale bentonite buffer experiments in all bentonite blocks but structural degradation of smectite could not be identified.

The influence of environmental factors and management methods on the vegetation of mesic grasslands in a central European mountain range

We examined how environmental factors combined with the diverse ways of the extensive management of mesic mountain grasslands affect species composition and diversity in the Polish part of Central Sudetes Mts. Based on the data from 100 research plots altitude, organic matter content and exchangeable magnesium in the soil, as well as the maximum soil water capacity and amount of sand fraction significantly affected species composition. Among the management methods, a significant effect on the differentiation of species composition was observed following the cessation of usage and mowing. Mown meadows had the highest share of forbs in the biomass, whereas those abandoned ones were dominated by tall and expansive grasses, mainly Calamagrostis epigejos. The species richest grasslands occurred in areas with soils of high water capacity, containing high concentrations of calcium and low amounts of total nitrogen. No significant effect of management methods on the total number of species as well as on the number of forb species was observed. Mown pastures had the highest mean value of the Shannon–Wiener diversity index.

Edaphic behaviour of several species of Cistus in the Green Corridor of Guadiamar (Spain) .

Species of the genus <em>Cistus </em>are woody shrubs that are noteworthy for their use in forest restoration, and have often been used as characteristic species of the higher syntaxonomical units. In this paper we address their limits of tolerance and optimum development in terms of edaphic factors. The area of study is the “Green Corridor” of Guadiamar, a narrow strip of land that connects two large protected sites: the “Doñana Natural Park and National Park” and the “Aracena y Picos de Aroche” and “Sierra Norte de Sevilla” Natural Parks in Andalusia (Spain). We worked with six species (<em>C. albidus, C. ladanifer, C. monspeliensis, C. populifolius, C. crispus</em> and <em>C. salviifolius</em>) detected at 14 sites. In each of these sites, a soil sample and a phytosociological inventory were taken. The soil variables analyzed were exchangeable calcium, exchangeable magnesium, exchangeable sodium, exchangeable potassium, total carbonate, moisture content at saturation and pH. Among sampled species, <em>C. albidus</em> is the most tolerant to presence of calcium and carbonate, with a soil pH preferably close to neutral or moderately basic. Although not strictly a calcareous species, its ability to compete is nevertheless favoured in these environments. <em>C. crispus </em>appears in the soils with the lowest exchangeable bases, total carbonates, pH and moisture content at saturation. <em>C. ladanifer</em> is noted in soils with a low level of total carbonates. <em>C. populifolius</em> is associated with the highest moisture content at saturation. <em>C. monspeliensis</em> is the species that has the largest tolerance range, especially for pH values, and is the most xerophytic. <em>C. salviifolius</em> presents an intermediate behaviour respect to most of the variables, with a preference for moderately acid environments, although no strictly.

제주지역 상동나무의 자생지 생육환경 및 식생조사

This study was carried out to investigate the vegetation and habitat environment of Sageretia thea which is distributed in Jeju island, Korea. Sageretia thea were mainly distributed to the west area in Jeju island. Soil pH and EC of Sageretia thea habitat were 5.8 and 0.34 dS  m �1 . The contents of organic matter, available phosphate, exchangeable potassium, exchangeable sodium, exchangeable magnesium and exchangeable calcium were 15.27%, 13.6 ㎎㎏ �1 , 0.27 cmol+㎏ �1 , 1.3 cmol+㎏ �1 , 1.7 cmol+㎏ �1 , 4.9 cmol+㎏ �1 , respectively. Thirty one taxa including 25 families, 31 genus, 27 species and 4 varieties were identified surrounding Sageretia thea habitat. Specific plant species were 1 taxon in III grade, 1 taxon in I grade and 3 taxa in I grade.

Effects of Conjunctive Use of Organic and Inorganic Sources of Nutrients on Soil Quality Indicators and Soil Quality Index in Sole Maize, Maize + Soybean, and Sole Soybean Cropping Systems in Hot Semi-arid Tropical Vertisol

The soils in the hot semi-arid tropical (SAT) regions generally have low organic matter and nutrient reserves. Soil-management problems in these soils primarily occur because of poor physical conditions and inadequate drainage through excess runoff, finally resulting in poor crop growth. Hence, the present investigation was conducted to study the long-term impact of conjunctive nutrient use treatments on soil quality indicators and soil quality indices under three cropping systems: (i) sole soybean, (ii) soybean + maize, and (iii) sole maize cropping systems at the Indore Centre of the All-India Coordinated Research Project for Dryland Agriculture (AICRPDA) using Navjot and JS-335 as cultivars of maize and soybean, respectively. In 2005, the soil quality assessment study under this experiment was undertaken after 8 years of experimentation. Soil quality assessment was done by identifying the key indicators using principal component analysis (PCA) and linear scoring technique (LST). Soil quality indices (SQI) and relative soil quality indices (RSQI) were also computed. Results revealed that most of the soil quality parameters were significantly influenced by the conjunctive nutrient management treatments. The common key indicators that emerged in all the treatments were pH, organic carbon (OC), exchangeable magnesium (Mg), available zinc (Zn), copper (Cu), manganese (Mn), and boron (B). The soil quality indices across the management treatments under sole maize system varied from 1.70 to 2.40 and application of 20 kg nitrogen (N) (compost) + 20 kg N through urea as top dressing emerged as a one of the most superior treatments with SQI value of 2.40. The soil quality indices in maize + soybean system varied from 1.12 to 1.47 and application of 20 kg N (compost) + 20 kg N through urea + azotobacter at 2 kg ha−1 proved to be significant with the greatest SQI value of 1.47. In the case of the sole soybean system, the SQI varied from 1.21 to 1.61. After considering all the systems together, the average best performance SQI score (ABP-SQI score) was computed, which varied from 1.14 to 1.56. The greatest value was recorded in the treatment with 20 kg N (compost) + 20 kg N (gliricidia) + 10 kg N (urea). The quantitative relationship developed in this study between mean soybean and maize yields (Y) and RSQI values (X), irrespective of the management treatments, could be quite useful to predict the yield quantitatively with respect to a given change in key indicators for these rainfed Vertisols.

CARACTERIZAÇÃO QUÍMICA DE DIFERENTES SISTEMAS DE USO DO SOLO

A forma de manejo que se utiliza nos solos amazônicos determina a sua utilização no futuro, assim a caracterização química é fundamental, pois é parâmetro para indicar a fertilidade desses solos. O objetivo deste trabalho foi realizar a caracterização química de diferentes usos de solos no estado do Pará. Foram coletadas quinze amostras simples para formar três amostras compostas com três repetições para cada área nos solos de várzea, capoeira e capoeira em transição para várzea com ampla faixa de variação de características químicas. As análises foram realizadas no departamento de solos na Universidade Federal Rural da Amazônia (UFRA). Foram realizadas as seguintes análises: O pH em água, cálcio, magnésio trocáveis, alumínio trocável e umidade atual. Em relação ao pH, todos os solos apresentaram acidez acentuada. Já para umidade, o solo de várzea foi que apresentou valor mais elevado. Para Ca2+ e Mg2+, os solos de várzea também foram que apresentou valores mais elevados. PALAVRAS-CHAVE: fertilidade, manejo do solo, química do solo.

Comparison of Conventional and Polymer Coated Urea as Nitrogen Sources for Lowland Rice Production

Nitrogen (N) is one of the most yield limiting nutrients in lowland rice production. Improving N use efficiency is essential to reduce cost of crop production and environmental pollution. A greenhouse experiment was conducted with the objective to compare conventional and polymer coated urea for lowland rice production. Grain yield, straw yield, panicle density, maximum root length, and root dry weight were significantly increased in a quadratic fashion with the increase of N rate from 0 to 400 mg kg−1 soil. Nitrogen source X N rate interactions for most of these traits were not significant, indicating that lowland rice responded similarly to change in N rates of two N sources. Based on regression equations, maximum grain yield was obtained with the application of 258 mg N kg−1 soil and maximum straw yield was obtained with the addition of 309 mg N kg−1 soil. Nitrogen use efficiency (grain yield per unit of N applied) was maximum for polymer coated urea compared to conventional urea. Root length and root dry weight improved at an adequate N rate, indicating importance of N fertilization in the absorption of water and nutrients and consequently yield. Polymer coated urea had higher soil exchangeable calcium (Ca) and magnesium (Mg), Ca saturation, Mg saturation, base saturation, and effective cation exchange capacity compared to conventional urea. There was a highly significant decrease in soil exchangeable potassium (K) with increasing N rates at harvest of rice plants.

Comparative Efficiency of Phosphorus Sources for Upland Rice Production

Rice (Oryza sativa L.) is a staple food for more than 50% of the world’s population, and phosphorus (P) is one of the most yield-limiting nutrients for rice production in tropical acidic soils worldwide. A greenhouse experiment was conducted to evaluate efficiency of six P sources for upland rice production. The P sources used were simple superphosphate (SSP), polymer-coated SSP (PSSP), triple superphosphate (TSP), polymer-coated TSP (PTSP), monoammonium phosphate (MAP), and polymer-coated MAP (PMAP). There were four P rates [50, 100 200, and 400 mg phosphorus (P) kg−1] applied with four sources plus one control treatment [0 mg phosphorus (P) kg−1]. Plant height, straw yield, grain yield, panicle density, root dry weight, maximum root length, and 1000-grain weight were significantly increased with increasing P rates in the range of 0 to 400 mg P kg−1. However, P-use efficiency (mg grain produced per mg P applied) was decreased with increasing P rate. Based on regression equation, overall maximum plant height was obtained with the application of 235 mg P kg−1, maximum straw yield with the application of 265 mg P kg−1, and maximum grain yield at 227 mg P kg−1. Based on maximum grain yield, the P source were classified as PMAP > SSP = MAP > PSSP > TSP > PTSP in the upland rice production efficiency. Overall, maximum panicle density was obtained with the addition of 231 mg P kg−1 and maximum 1000-weight was obtained with the addition of 226 mg P kg−1. Similarly, overall root dry weight and maximum root length were achieved with the application of 261 and 298 mg P kg−1 of soil. Most of the growth and yield components had a significant positive association with grain yield. Optimum soil acidity indices such as pH; exchangeable calcium (Ca), magnesium (Mg), and potassium (K); Ca, Mg, and K saturation; base saturation; and acidity saturation were established for maximum upland rice grain yield.

Bio-Revegetation Impact on the Physicochemical Characteristics of a Sandy Quarry Soil in Terga Beach Region in Algeria

In order to define the impact of a bio-revegetation effect on soil physicochemical properties, we used Acacia Saligna in variants with bio-fertilizers such as rhizobia and mycorrhizae that play a key role in the productivity and sustainability of soil as well as the environmental protection. The area of study is a degraded sandy quarry in Terga, a coastal semi-arid area located in the northwestern part of Algerian. Our sampling and analysis of soil were made after each trimester of experiments in the fields, using four blocks, each one containing ten plots. Sampling is a composite of soil that was made in each plot diagonally on a depth of 10 cm and a diameter of 30 cm from the plant, at different times: first trimester (3 months), second (6 months), and third (9 months). Preliminary results showed a real and favorable modification of substrates by obtaining materials with less alkaline pH, there is a significant phosphorus increase in the second and third trimester compared to the first trimester, however the soil calcareous nature prevents the expression of some parameters resulting in a small improvement in total nitrogen and a deficiency in both exchangeable magnesium and organic matter.

Determination of spatial variability of some magnesium forms in Phaeozem using geostatistical methods

The spatial variability analysis of soil properties facilitates the prediction of their contents across various sites, useful for design of site-specific farming practices. Intrapopulation and spatial variation of soil available (Mg-A), exchangeable (Mg-E) and water-soluble (Mg-H2O) magnesium forms was evaluated in a field on Phaeozem soil, located in the village Orlinek near Mrocza, in the Province of Kujawy and Pomorze (wojewodztwo kujawsko-pomorskie), north-western Poland. Soil samples were collected from an area of 0.5 ha situated within an 80-hectare arable field. In April 2007, 50 soil samples were collected in a 10 x 10 m grid square pattern from the field cropped with winter wheat. The content of Mg forms was analyzed with descriptive statistics and the geostatistic modeling of semivariograms to plot variability maps. The Mg-A content ranged from 4.9 to 12.2 mmol kg -1 , while the Mg-E form varied from 5.6 to 16.4 mmol kg -1 . The average content of Mg-H 2 O was 1.27 mmol kg -1 . All the properties revealed a normal content distribution, which coincided with similar values of means, medians and significantly lower values of standard deviations (SD) than the means. Moderate variability of all the Mg forms content was confirmed by the coefficient of variation (CV%), falling within 19.4-23.6%. The spatial dependence of the Mg forms content was evaluated by the use of semivariograms and krigged maps. The parameters of variogram models, except for the Mg-A content, revealed a share of random variance (a nugget) in total variability (sill). The content of Mg-E demonstrated high spatial dependence (the nugget effect <25%), while the content of Mg-H2O and the percentage share of Mg-E in the sum of base cations (S) fell within the moderate class of spatial variability (the nugget effect between 25% and 75%). The spatial correlation of the properties studied was assessed by 11.1 to 21.3 m range. The spatial variation maps showed that the Mg-A and Mg-E contents had a similar distribution in the research area, while the Mg-H2O content and the percentage of the Mg-E in (S) presented a different pattern of variability. The maps revealed that almost 80% of the field showed a very high Mg-A content (Class I abundance), which suggested that Mg fertilizer is unnecessary.

Spatial-temporal character of exchangeable magnesium and its influencing factors at tobacco-growing soil region in Shaoyang

In order to understand the distribution of exchangeable magnesium content for tobacco-growing soils in Shaoyang, exchangeable magnesium content and its influencing factors such as pH, organic matter were analyzed using traditional statistics and geostatistics based on 1 790 observed soil samples. The results showed: ①The exchangeable magnesium content in the tobacco-growing soil was in lower level,with a mean of 0.78 cmol/kg and variation coefficient of 51.39%, and about 16.98% of exchangeable magnesium content in the observed soil samples was suitable for tobacco cultivation. ②The exchangeable magnesium content in tobacco-growing soils in Longhui and Shaoyang counties were significantly higher than that of in Xinning county; From the map interpolated by Kriging, the tendency of spatial variation of exchangeable magnesium decreased from north to south; Compared to the results of soil survey in 2002, the exchangeable magnesium in tobacco soils showed a decreased tendency. ③A quadratic curve relationship was found between exchangeable magnesium and soil pH value. If the pH value was lower than 5.0, the exchangeable magnesium was in the state of insufficiency or latent insufficiency; There was no apparent relationship between exchangeable magnesium and organic matter for tobacco-growing soils.

Influence of Lime and Gypsum on Yield and Yield Components of Soybean and Changes in Soil Chemical Properties

Soybean is one of the most important legume crops in the world. Two greenhouse experiments were conducted to determine the influence of liming and gypsum application on yield and yield components of soybean and changes in soil chemical properties of an Oxisol. Lime rates used were 0, 0.71, 1.42, 2.14, 2.85, and 4.28 g kg−1 soil. Gypsum rates applied were 0, 0.28, 0.57, 1.14, 1.71, and 2.28 g kg−1 soil. Lime as well as gypsum significantly increased grain yield in a quadratic fashion. Maximum grain yield was achieved with the application of 1.57 g lime per kg soil, whereas the gypsum requirement for maximum grain yield was 1.43 g per kg of soil. Lime significantly improved soil pH, exchangeable soil calcium (Ca) and magnesium (Mg) contents, base saturation, and effective cation exchange capacity (ECEC). However, lime application significantly decreased total acidity [hydrogen (H) + aluminum (Al)], zinc (Zn), and iron (Fe) contents of the soil. The decrease in these soil properties was associated with increase in soil pH. Gypsum application significantly increased exchangeable soil Ca, base saturation, and ECEC. However, gypsum did not change pH and total acidity (H + Al) significantly. Adequate soil acidity indices established for maximum grain yield with the application of lime were pH 5.5, Ca 1.8 cmolc kg−1, Mg 0.66 cmolc kg−1, base saturation 53%, Ca saturation 35%, and Mg saturation 13%. Soybean plants tolerated acidity (H + Al) up to 2.26 cmolc kg−1 soil. In the case of gypsum, maximum grain yield was obtained at exchangeable Ca content of 2.12 cmolc kg−1, base saturation of 56%, and Ca saturation of 41%.

Soil fertility changes following conversion of grassland to oil palm

Impacts of palm oil industry expansion on biodiversity and greenhouse gas emissions might be mitigated if future plantings replace grassland rather than forest. However, the trajectory of soil fertility following planting of oil palm on grasslands is unknown. We assessed the changes in fertility of sandy volcanic ash soils (0–0.15 m depth) in the first 25 years following conversion of grassland to oil palm in smallholder blocks in Papua New Guinea, using a paired-site approach (nine sites). There were significant decreases in soil pH (from pH 6.1 to 5.7) and exchangeable magnesium (Mg) content following conversion to oil palm but no significant change in soil carbon (C) contents. Analyses to 1.5 m depth at three sites indicated little change in soil properties below 0.5 m. There was considerable variability between sites, despite them being in a similar landscape and having similar profile morphology. Soil Colwell phosphorus (P) and exchangeable potassium (K) contents decreased under oil palm at sites with initially high contents of C, nitrogen, Colwell P and exchangeable cations. We also assessed differences in soil fertility between soil under oil palm (established after clearing forest) and adjacent forest at two sites. At those sites, there was significantly lower soil bulk density, cation exchange capacity and exchangeable calcium, Mg and K under oil palm, but the differences may have been due to less clayey texture at the oil palm sites than the forest sites. Cultivation of oil palm maintained soil structure and fertility in the desirable range, indicating that it is a sustainable endeavour in this environment.

Influence of lime and gypsum on long-term rehabilitation of a Red Sodosol, in a semi-arid environment of New South Wales

This paper determines the influence of lime and gypsum on the rehabilitation of a degraded sodic soil in a semi-arid environment 12 years after application. The aim was to assess rehabilitation strategies for sodic soils as alternatives to the application of gypsum alone. An experimental site was used where lime and gypsum combinations (L0G0, lime 0 t ha–1 and gypsum 0 t ha–1; L0G1, L0G2.5, L0G5, L1G0, L2.5G0, L5G0, L1G1, L2.5G1) had been applied 12 years prior, in 1994. An earlier study had reported on the effects after 3 years of the chemical ameliorants and tillage on a range of soil physical and chemical properties at the site. The current study, sampled in 2006, assessed the effects after 12 years of lime and gypsum on soil chemistry, stability, hydraulics, vegetative growth and soil respiration. Calcium, primarily from lime, was observed to have a major effect on soil health. Significant effects on soil chemistry were limited to increases in exchangeable calcium and decreases in exchangeable magnesium, although aggregate stability in water and hydraulic conductivity were significantly improved where L5G0 was applied. Vegetation patch width, total nitrogen and carbon, and soil respiration were significantly improved where lime had been added at 2.5 or 5 t ha–1. As no lime could be detected in the soil 12 years after application, it was deduced that lime had acted as a catalyst for increased functionality in soil and vegetation interactions. This increased soil functionality resulted in an increased rate of lime dissolution in the soil.

Chemical attributes of soil fertilized with cassava mill wastewater and cultivated with sunflower.

The use of waste arising from agroindustrial activities, such as cassava wastewater, has been steadily implemented in order to reduce environmental pollution and nutrient utilization. The aim of this study is that the changes in chemical properties of dystrophic red-yellow latosol (oxisol) were evaluated at different sampling times after reuse of cassava wastewater as an alternative to mineral fertilizer in the cultivation of sunflower, hybrid Helio 250. The experiment was conducted at the Experimental Station of the Agricultural Research Company of Pernambuco (IPA), located in Vitória de Santo Antão. The experimental design was randomized blocks with 6 × 5 subplots; six doses of cassava wastewater (0; 8.5; 17.0; 34.0; 68.0; and 136 m3 ha−1); and five sampling times (21, 42, 63, 84, and 105 days after applying the cassava wastewater), with four replications. Concentrations of available phosphorus and exchangeable potassium, calcium, magnesium and sodium, pH, and electrical conductivity of the soil saturation extract were evaluated. Results indicate that cassava wastewater is an efficient provider of nutrients to the soil and thus to the plants, making it an alternative to mineral fertilizers.

Mudflat soil amendment by sewage sludge: Soil physicochemical properties, perennial ryegrass growth, and metal uptake

The fast pace of cropland loss in China is causing alarm over food security and China’s ability to remain self-reliant in crop production. Mudflats after organic amendment can be an important alternative cropland in China. Land application of sewage sludge has become a popular organic amendment to croplands in many countries. Nevertheless, the land application of sludge to mudflats has received little attention. Therefore, the objective of the present work was to investigate the impact of sewage sludge amendment (SSA) at 0, 30, 75, 150 and 300 t ha−1 rates on soil physicochemical properties, perennial ryegrass (Lolium perenne L.) growth and heavy metal accumulation in mudflat soil. The results showed that the application of sewage sludge increased organic matter (OM) content by 3.5-fold while reducing salinity by 76.3% at the 300 t ha−1 rate as compared to unamended soil. The SSA reduced pH, electric conductivity (EC) and bulk density in mudflat soil, increased porosity, cation exchange capacity (CEC) and contents of nitrogen (N), phosphorus (P), exchangeable potassium ions (K+), sodium ions (Na+), calcium ions (Ca2+) and magnesium ions (Mg2+) in comparison to unamended soil. There were 98.0, 146.6, 291.4 and 429.2% increases in fresh weight and 92.5, 132.4, 258.6 and 418.9% increases in dry weight of perennial ryegrass at 30, 75, 150, and 300 t ha−1, respectively, relative to unamended soil. The SSA increased metal concentrations of aboveground and root parts of perennial ryegrass (p < 0.05). The metal concentrations in perennial ryegrass were Zn > Cr > Mn > Cu > Cd > Ni, and the metal concentrations in roots were significantly higher than aboveground parts. The metal accumulation in perennial ryegrass correlated positively with sludge application rates and available metal concentrations in mudflat soil. Land application of sewage sludge was proved to be an effective soil amendment that improved soil fertility and promoted perennial ryegrass growth in mudflat soil. However, heavy metal accumulation in plants may cause food safety concern.