Soil Exchangeable Potassium Research Articles

Influence of climate, soil and vegetation diversity on the leaf area index as measured by canopy hemispherical photography in tropical rainforests across a wide elevational gradient

Tropical rainforests (TRFs) play an important role in regulating the global climate and conserving biodiversity. Leaf area index (LAI) determines the capacity of TRFs for radiation interception and carbon sequestration via photosynthesis while also influencing the water loss from TRF canopies via transpiration. Elevational gradients in tropical environments provide an approach to investigate the influence of environmental variations on key vegetation properties such as the LAI. In this work we determined the concurrent, interactive influences of the elevational gradients of the environment (i.e. selected climatic and soil properties) and vegetation (tree diversity and structure) in determining the variation of LAI of one-hectare permanent sampling plots (PSPs) within TRFs across a wide elevational gradient (from 117 m to 2132 m above sea level). Eight rounds of canopy hemispherical photography were carried out at three-month intervals over a 24-month period from 2019 to 2022. Canopy LAI was estimated using HemiView image processing software. Long-term mean climatic data from 1990 to 2021 were extracted for the PSPs from monthly global weather database of CRU-TS-4.06-bias corrected with WorldClim-2.1. Key soil properties were measured at 0–15 cm and 15–30 cm depths via soil sampling. Tree diversity was determined by a complete census of all trees with equal or greater than 10 cm in diameter at breast height. Total tree biomass was estimated using allometric equations. Linear mixed model analysis of LAI showed significant (p < 0.05) variance for the random effects of elevation and elevation × time interaction. In a majority of measurement rounds, variance of LAI due to elevation was significant while at a majority of elevations, the fixed effect of measurement round on LAI was significant. Leaf area index showed significant linear reductions with elevation in all rounds, at rates ranging from 0.175 to 0.357 per 1000 m. Linear and multiple regression analyses identified increasing maximum cumulative soil water deficit, CSWDMax (an index of water deficit computed as the difference between evapotranspiration and precipitation), as the major climatic factor responsible for the reduction of LAI with elevation. Decreasing solar irradiance (SR) and increasing day-night temperature difference (DTR) with elevation also contributed to the observed LAI trend. Multiple regression analysis showed soil exchangeable potassium (KEx) and available phosphorus (PAv) influencing LAI positively while electrical conductivity (EC) and total nitrogen (NTot) influencing LAI negatively. Variation of Shannon-Wiener tree diversity index (H) and total tree biomass per hectare (TBM) contributed positively to the observed elevational variation of LAI. Factor analysis extracted two underlying factor constructs which accounted for 86 % of the combined variation in climate, soil and vegetation across the elevational gradient. Plot-wise scores of Factor 1, which had CSWDMax, SR, DTR, soil EC, NTot and H loading strongly and accounting for 70 % of the variation, showed a significant linear relationship with LAI. A cluster analysis incorporating the elevational variation of LAI, climate, soil and vegetation clearly classified the TRFs into four ranges of elevation at a linkage distance of 0.75. We conclude that LAI of TRFs in our study decreases with increasing elevation and identify increasing water deficits with elevation as the major climatic factor controlling this reduction.

Use of random forest algorithm for predictive modelling of transfer factor soil-plant for radiocaesium: A feasibility study

A German dataset with soil-plant transfer factors for radiocaesium including many co-variables was analysed and prepared for the application of the Random Forest (RF) algorithm using the R libraries 'party', and 'caret'.A RF predictive model for soil-plant transfer factor was created based on 10 co-variables. These are, for example, taxonomic plant family, plant part, soil type and the exchangeable potassium concentration in the soil. The RF model results were compared with the results of two (semi-)mechanistic models. Of the more than 3000 entries in the original dataset, only about 1200 could be used, as this was the largest complete dataset with the largest number of co-variables available.The obtained RF predictive model can reproduce the experimental observations better than the two (semi)-mechanistic models, which are based on many assumptions and fixed parameter values. Model performance was quantified using the metrics of Root Mean Square Error (rmse) and Mean Absolute Error (mae). The RF model was able to reproduce the variability of the data by up to 6 orders of magnitude. The categorical co-predictors, especially taxonomic plant family and plant part, have a greater influence than the numerical co-predictors, such as pH and exchangeable soil potassium concentration.This feasibility study shows that RF is a promising tool to obtain predictive models for transfer factors. However, to build a widely applicable predictive model, a dataset is needed that contains at least thousands of entries for transfer factors and for the most important co-variables and considers a large parameter space.

Soil Fertility Evaluation for Cashew Production at Iyapo Farm Estate, Offa, Kwara State

Cashew (Anacardium occidentale L) is an important commodity crop with great potential as a foreign exchange earner. It is grown principally for it nuts and apple and is a hardy crop which is adapted to a wide range of agro-ecologies. The increase in the price of cashew nuts globally, has resulted in increased interest in the cultivation of cashew. The Management of Iyapo farms limited in its desire to key into this sector requested the technical assistance of Cocoa Research Institute of Nigeria (CRIN) to carry out soil fertility evaluation of the 50 hectares of land proposed for establishment of cashew. The farm was divided into three main sections (A, B and C) based on topography and four land use types (water logged, cassava plot, previously cultivated land and excavated land). Section A was parallel to River Oyun followed by section B in the middle of the farm, while the last section C ran parallel to the road from Ijagbo town. The land use types were scattered within the three blocks. The water logged area was however confined only to section A which was close to river Oyun.&#x0D; Soil samples were collected at soil depths of 0-20 cm and 20-40 cm soil depth and at a distance of 20 m apart. The soil collected was put in nylon bags and properly labelled. Soil samples collected were air dried, passed through 2 mm sieve and analyzed for some of its physical and chemical properties. In section A, total soil nitrogen at 0-40 cm soil depth ranged between 0.07 g kg-1 to 0.18 g kg-1 with a mean value of 0.11 gkg-1 soil while mean soil available phosphorus at 0-40 cm soil depth was 3.16 mg kg-1 The exchangeable potassium content across 0-40 cm soil depth ranged between 0.09cmol kg-1 to 0.35 cmol kg-1 with a mean value of 0.25 cmolkg-1 and 0.19 cmol kg-1 for 0-20 cm and 20-40 cm soil depth respectively. In section B, nitrogen across the various soil depths ranged between 0.04 gkg-1 to 0.12 gkg-1 with nitrogen content of the soil decreasing with increasing soil depth. This falls below the soil critical level of 1 gkg-1 required for cashew and was grossly inadequate to meet nitrogen need for cashew. There is need for nutrient supplementation as nitrogen fertilizer is required to meet the nitrogen needs of the cashew. Similarly, phosphorus was also inadequate across the soil depths with a range of 2.47 mgkg-1 to 4.51 mgkg-1 across the various soil depth and a mean value of 3.24 mgkg-1 and 2.65 mgkg-1 for 0-20 cm and 20-40 cm soil depths respectively. This was below the soil critical value of 3.7 mgkg-1. There is therefore need to apply phosphorus fertilizer to boost cashew productivity.&#x0D; Soil exchangeable potassium was adequate across the various soil depths with a range of 0.13 to 0.20 cmol kg-1 and a mean value of 0.18 cmol kg-1 and 0.16 cmol kg-1 for 0-20cm and 20-40 cm soil depths respectively. There is no need for potassium fertilizer application. The results above indicated that sections A, B and C requires 180 kg ha-1 of urea and 31.5 kg of Single Super Phosphate (SSP). The cassava plot and previously cropped bare land requires 189 kg ha-1 urea and 9.9 kg ha-1 SSP, while the excavated land requires 194.2 kg urea 25.8 kg SSP and 32.28 kg MOP. Cashew should not be grown on the water-logged section.

Assessment of suitability of abandoned lands for oats cultivation based on the forecast of the yield according to long-term monitoring data (the case of a specific farm)

The paper presents the results of predicting the yield of oats in the conditions of abandoned lands of the former pilot production farm (PPF) of the All-Russian Research Institute of Reclaimed Lands, located in the center of the Tver region. There were used the data of long-term monitoring (1997-2020) of the yield of this crop in clean and cover crops (with under-sowing of grasses) on the agroecological transect of the Gubino agroecopolygon located within the PPF. With the help of statistical and mathematical modeling, regularities in the formation of oat yields within the transect were revealed. On the basis of these formulas, predicted oat yields were calculated for the entire territory of abandoned lands, and maps of its variability under the conditions of the protected area and measures for intensifying grain production were also created. It has been established that oats in pure crops react most strongly to the content of exchangeable potassium in soils, to water supply and humus content, while in cover crops the yield largely depends on mobile phosphorus in the soil and the degree of illumination and swampiness of the territory. More than 92 % of the PPF area is potentially capable of providing oat yield in clean crops from 2.7 to 3.1 centners/ha, and an increased oat yield (3.0-3.3 centners/ha) in cover crops can be obtained only on ≈ 44 % of the farm area. The main methods for increasing the yield of oats in pure crops are the application of potash and organic fertilizers, as well as the preservation of moisture in the soil, while expanding the area of cover crops involves the use of oat varieties that react poorly to excess phosphorus in the soil. Intensification of oat production in clean crops is possible on the area of 6026 ha, and in cover crops only 790 ha, since in the rest of the territory its productivity is limited by insufficient illumination and waterlogged soils.

Radiocesium transfer from soil is lower in tall fescue than orchardgrass under conditions of lower soil exchangeable potassium

AbstractIn Japan, additional potassium fertilization is used as a countermeasure for radiocesium‐contaminated grasslands in the Tohoku and North Kanto regions. A 2‐year pot experiment was conducted to assess the efficacy of using tall fescue (Festuca arundinacea Schreb.), a low‐cesium‐absorption grass species, to replace orchardgrass (Dactylis glomerata L.), the most common forage grass species in these regions, to reduce potassium fertilization and improve the forage mineral balance. The treatments were a combination of two grass species (tall fescue and orchardgrass) and two potassium application rates (0 [K0] and three times the conventional amount [K3]) with four replications. The grass species and potassium application rate had significant (p &lt; .001) effects on plant cesium‐137 concentrations. The results of the generalized linear mixed‐model analysis indicated that when tall fescue replaced orchardgrass, cesium‐137 in the forage grass was reduced to 34% and that the K3 treatment reduced cesium‐137 to 46% relative to the K0 treatment. The difference in cesium‐137 concentration between the two grass species increased as the soil exchangeable K2O content decreased. The equations for estimating the cesium‐137 concentration (y [g/kg]) from the exchangeable K2O content (x [g/kg]) were obtained as y = 63.7e–2.095x for tall fescue and y = 185.5e–3.327x for orchardgrass. These equations indicate that tall fescue cultivation can reduce the risk of elevated radioactive Cs in the grass by reducing potassium fertilizer to approximately half that of orchardgrass. There were no differences in the response of plant potassium concentrations or the potassium/(calcium + magnesium) equivalent ratio to soil exchangeable K2O content among the grass species. However, the mineral balance of forage can be improved by reducing potassium fertilizer applications for cesium‐137 remediation. Tall fescue has good potential to remediate contaminated grasslands as it reduces additional potassium fertilization and improves the mineral balance of forage.

Few functionally acquisitive big-sized trees restrict but soil nutrients promote soil organic carbon storage in temperate deciduous forests

Soil organic carbon (SOC) storage plays a crucial role in mitigating global climate change while maintaining forests and sustaining environmental conditions. Recent studies have shown that plant species diversity increases SOC storage in experimental grasslands and natural forests. Here, we aim to show how an integrating tree-size and trait-based ecological approach leads to mechanistic insights into SOC storage that may be overlooked in previous studies. We hypothesized that tree functional diversity effects on SOC storage would change with tree-sized-based species' functional strategies driven by soil properties in natural temperate deciduous forests. We used the forest inventory data, site-specific measured traits and soil properties from 99 temperate deciduous forest plots in northwestern Iran. We investigated the joint effects of topographic factors, soil chemical properties, and the functional attributes (multi-trait functional diversity indices and community-weighted trait mean indices) of big-sized trees (BsT; individual tree diameter ≥ 50 cm) and remaining-sized trees (RsT) on topsoil (0–30 cm) SOC storage. The multiple linear regression models showed that SOC storage increased with increasing soil available phosphorus (r = 0.36), soil exchangeable potassium (r = 0.27 to 0.31) and soil total nitrogen (r = 0.27). In contrast, SOC storage declined with increasing the community-weighted mean of specific leaf area (r = −0.38 to −0.40). The structural equation model showed that SOC storage was directly driven by the positive effect of soil nutrients (i.e. a latent variable of soil total nitrogen and available phosphorus; r = 0.42) and the negative effect of the community-weighted mean of specific leaf area (r = −0.31). The topographic factors as well as the other several functional attributes of BsT and RsT showed non-significant direct and indirect effects on SOC storage in both types of statistical modelling. Our study suggests that the mass ratio and soil fertility rather than the niche complementarity effects along with the big-sized trees effect regulates SOC storage through the acquisitive trait identity of BsT species as compared to RsT species in temperate deciduous forests. We argue that maintaining high levels of species diversity with the most efficient trait identity across tree sizes is important for biodiversity conservation and multiple forest functions such as SOC storage which should be a priority for plantation management plans or silvicultural practices in natural forests.

Towards a better understanding of linear species distribution in river valleys: The abundance of river corridor plants is linked to soil exchangeable potassium and pH

The phenomenon that some vascular plant species grow mainly or exclusively in the large river valleys of Central Europe constitutes a long-standing distribution puzzle. In our study, we focused on determining which physicochemical properties of soil affect the distribution of river corridor plant (RCP) species. Research that included RCP coverage, the physicochemical properties of soil as well as several topographic and spatial variables were conducted in 10 transects perpendicular to the San River (SE Poland). The sampled plots were located both in close proximity to the river, where the greatest number of RCP populations are concentrated, and along anthropogenic linear landscape elements which have proven to be important for RCP occurrence in areas located away from the riverbed. Spearman rank correlation matrices were constructed to observe the general relationships between particular variables and Boosted Regression Tree models were used for explaining RCP coverage. Our study indicated that in the case of plots located in proximity to the river, the expected coverage of RCP species was highest in plots characterized by a higher soil exchangeable potassium (K) content, as well as in those located closer to the San River and at lower altitudes. In plots situated along anthropogenic linear landscape elements, the expected coverage of RCPs was highest in plots with a high soil exchangeable K content and in those with a high soil pH. The analyses clearly showed that the physicochemical properties of soils indeed affect RCP species occurrence and they require soils with a high exchangeable K content and a high pH. Since these two soil parameters are closely related to soil fertility, and additionally K enhances root development, we suppose that both factors strengthen the competitiveness of RCPs in floodplain ecosystems.

Effect of shifting cultivation and fallow on soil quality index in Mokokchung district, Nagaland, India

BackgroundShifting cultivation is a major agriculture practice in the Nagaland state of India. This study examines the effect of shifting cultivation and the length of the fallow period on soil quality index (SQI). Four sites were selected for the study, viz., a shifting cultivation site (SCS), a 3-year-old fallow land (FL-3), a 7-year-old fallow land (FL-7), and a 12-year-old fallow land (FL-12). Soil parameters were recorded seasonally and SQI was calculated from the minimum data set.ResultsWith the increase in the fallow period, the values of conductivity, soil organic carbon, available nitrogen, available phosphorus, exchangeable potassium, moisture, clay, and cation exchange capacity of soil increased. Meanwhile, soil pH and bulk density decreased with fallow duration. The additive SQIa values were in the order SCS < FL-3 < FL-12 < FL-7; meanwhile, the weighted SQIw values were in the order SCS < FL-3 < FL-7 < FL-12. It is also observed that the SQI value decreases with the increase in soil depth under both the weighted and additive indexes. SCS with the lowest SQI value reflects the reduced soil organic carbon (SOC) and macronutrients. Increased SOC levels in site FL-12 (2.88–3.94%) may be one reason for its higher SQI value.ConclusionsOur study highlights that unsustainable practices of shifting cultivation and reduction in the fallow period negatively affect soil quality. Furthermore, the study also recommends the use of the weighted method of SQI as it agrees with the reports of land use causing alteration in the soil quality. Our findings may be utilized to quickly access and disseminate information to the stakeholders and aid in constructing local soil quality index maps of the region. There is an urgent need for a rapid, cost and resource-efficient soil quality assessment and SQI may be one tool that achieves this goal.

Prediction of exchangeable potassium in soil through mid-infrared spectroscopy and deep learning: From prediction to explainability

The ability to characterize rapidly and repeatedly exchangeable potassium (Kex) content in the soil is essential for optimizing remediation of radiocaesium contamination in agriculture. In this paper, we show how this can be now achieved using a Convolutional Neural Network (CNN) model trained on a large Mid-Infrared (MIR) soil spectral library (40,000 samples with Kex determined with 1 M NH4OAc, pH 7), compiled by the National Soil Survey Center of the United States Department of Agriculture. Using Partial Least Squares Regression as a baseline, we found that our implemented CNN leads to a significantly higher prediction performance of Kex when a large amount of data is available (10000), increasing the coefficient of determination from 0.64 to 0.79, and reducing the Mean Absolute Percentage Error from 135% to 31%. Furthermore, in order to provide end-users with required interpretive keys, we implemented the GradientShap algorithm to identify the spectral regions considered important by the model for predicting Kex. Used in the context of the implemented CNN on various Soil Taxonomy Orders, it allowed (i) to relate the important spectral features to domain knowledge and (ii) to demonstrate that including all Soil Taxonomy Orders in CNN-based modeling is beneficial as spectral features learned can be reused across different, sometimes underrepresented orders.

EFFECTS OF DIFFERENT TILLAGE PRACTICES ON SOIL FERTILITY PROPERTIES: A REVIEW

Soil tillage is an important factor affecting soil fertility properties and crop yield. Tillage impact certain soil physical and chemical properties such as bulk density, soil porosity and water-holding capacity, infiltration rates, hydraulic conductivity, soil temperature, soil organic carbon, pH, CEC, available nitrogen, phosphorus and exchangeable potassium amongst others. The main objective of the present work was to compare the effect of no-tillage systems and the conventional tillage systems. Tillage systems can be generally categorized into plow tillage (conventional tillage), reduced tillage using chisel plow, disc plow, harrow disc or cultivators and no-till systems. Conservation tillage and its various types generally improve the soil quality indicators including soil organic carbon (SOC) storage. Whereas, conventional tillage practices give birth to a finer and loose-setting soil structure with a modified soil bulk density and soil moisture content, hence, causing loss of soil organic carbon and deterioration in other soil properties. Generally, soil fertility properties are more favourable with no-till than tillage-based systems. However, some researchers observed no significant effect of tillage methods (no-tillage and plow till) on bulk density (BD), pH and total porosity, while others found otherwise. The magnitude of these discrepancies could be due to the differences in crop species, soil properties, climatic characteristics and their complex interactions as well as tillage system adopted.

Linkages among Soil Fertilization Regimes, Chemical Properties and Maize Grains Yield in Humid Tropic

We hypothesize that there is a linkage among different soil fertilization regimes, soil chemical attributes and maize grains yield. We aimed to evaluate the relationships between different soil fertilization regimes, soil chemical properties and maize grains yield. The experiment was performed in northeastern Brazil, in a randomized block design, at an area divided into 24 plots with six treatments and four replicates (Nitrogen (N); Leucaena (L); Nitrogen+Leucaena (N+L); Humic Acid+Leucaena (HA+L); Humic Acid+Nitrogen (HA+N) and Humic Acid+Nitrogen+Leucaena (HA+N+L)). Each plot was cropped with maize (Zea mays L.) and the grains yield was estimated. Soil samples were collected at depths of 0–5 cm, 5–10 cm and 10–20 cm. Potential acidity, pH, soil organic carbon (SOC), available phosphorus, exchangeable potassium, calcium and magnesium, cation exchange capacity (CEC), sum of basic cations (SBC) and base saturation (BS) were determined. Principal component analysis (PCA) was used to correlate soil chemical attributes with maize yield. Calcium, magnesium, available P and SBC were related to the maize grains yield in upper soil layer, especially at nitrogen fertilization. This research confirms the hypothesis that there is a linkage between different soil fertilization regimes, soil properties and the maize grains yield.

Soil Application of Zeolite Affects Inorganic Nitrogen, Water Soluble and Exchangeable Potassium

An incubation study was conducted at college of agriculture, rajendranagar, PJTSAU to evaluate the influence of zeolite application on inorganic nitrogen, water soluble and exchangeable potassium in soil. Clinoptilolite Zeolite was fully mixed with soil (7.5 t ha-1) at the start of the experiment. Nitrogen was applied to soil through urea (200 kg ha-l). The experiment was conducted for 35 days and soil was analyzed for inorganic nitrogen, water soluble and exchangeable potassium at weekly intervals i.e., 1, 7, 14, 21, 28, 35 days of incubation. The results indicated that the treatment with zeolite application showed significantly higher ammoniacal nitrogen from day 1 (136.54 mg kg-l) to day 35 (38.71 mg kg-l) as well as nitrate nitrogen (day 1 – 59.13 mg kg-l; day 35 – 130.13 mg kg-l). Similarly water soluble (day 1 – 92.21 kg ha-l; day 35 – 103.13 kg ha-l) and exchangeable potassium (day 1 – 363.69 kg ha-l; day 35 – 393.94 kg ha-l) was also significantly higher in zeolite applied treatments. Thus, mixing of zeolite into soil improves inorganic nitrogen through reducing leaching losses and also improves water soluble and exchangeable potassium.

Impact of Organic Amendment with Alternate Wetting and Drying Irrigation on Rice Yield, Water Use Efficiency and Physicochemical Properties of Soil

A pot experiment was executed to investigate the impact of biochar and compost with water-saving irrigation on the rice yield, water use efficiency, and physicochemical properties of soil. Two irrigation regimes—namely alternate wetting and drying (AWD) and continuous flooding (CF)—and four types of organic amendments (OA)—namely rice husk biochar (RHB), oil palm empty fruit bunch biochar (EFBB), compost and a control—were applied to evaluate their effects. Under the AWD irrigation regime, the maximum grain was produced by RHB (241.12 g), whereas under the same organic amendments, both AWD and CF produced a similar grain yield. Under the same organic amendment, a significantly higher water use efficiency (WUE) was observed from the AWD irrigation with RHB (6.30 g L−1) and EFBB (5.80 g L−1). Within the same irrigation regime, soil pH, cation exchange capacity, total carbon, total nitrogen and available phosphorus were enhanced due to the incorporation of biochar and compost, while higher soil exchangeable potassium was observed under CF irrigation for all treatments. RHB and EFBB significantly reduced the soil bulk density (up to 20.70%) and increased porosity (up to 16.70%) under both irrigation regimes. The results imply that the use of biochar with AWD irrigation could enhance the nutrient uptake and physicochemical properties of soil and allow rice to produce a greater yield with less water consumption.

Investigating the Effect of Long-Term Sugarcane Cultivation on Some Soil Properties of Soils in Karoun Agro-industry Unit, Khuzestan Province, Iran

The principal aim of the present research was investigation of the effect of long-term sugarcane cultivation on some chemical and physical properties of soil in Karoun Agro-industry Unit in Shoushtar city, Iran. The study was conducted in a factorial arrangement based on randomized complete block design with two field factors at 8 levels and three depths in three replications. Soil samples were collected and some of their physical (e.g., bulk density) and chemical (e.g., pH, EC, soil available phosphorus, organic carbon, soluble sodium and available potassium) Features9 were measured. Results revealed that land use change and long-term sugarcane cultivation reduced electrical conductivity, the amount of soluble sodium and available potassium contents of soil in different depths, while caused increasing the percentage of organic matter and available soil phosphorous. However, at similar experimental conditions, no significant changes were observed in soil pH. The soil bulk density contents in farms under continuous cultivation of sugarcane, was more than the control field and HARZA. Moreover, soil exchangeable potassium was identified as a sensitive indicator of long-term sugarcane cultivation.

Linking soils and streams during events: response of stream water K+ concentration to soil exchangeable K+ concentration in small catchments with fragipan soils (Carpathian Foothills, Poland)

Abstract The study aimed to determine the linkage between soil exchangeable potassium (K+) concentration and stream water K+ concentration during rainfall and snowmelt events in small catchments with different land use (Carpathian Foothills, Poland). The complementary geochemical and hydrochemical approach used in the study produced new information on the role of particular soil horizons and contributing areas such as hillslope or riparian areas in K+ delivery to stream channels during events. Horizons lying above the nearly impermeable fragipan (Btx) play the most important role in the process of K+ influx to streams during most event types except snowmelts with frozen soils, in all the studied catchments. In the woodland catchment, rapid flushing of K+ from the topsoil Ah horizon with higher hydraulic conductivity (Ksat ) and higher exchangeable K+ concentrations than in the lying lower E horizon resulted in a clockwise hysteresis of K+ in stream water during most events. In agricultural catchments, changes in stream water K+ concentration during events were determined by distinct differences between soil exchangeable K+ concentrations on hillslopes and in riparian areas.

Impacts of land‐use changes on soil fertility in Okomu Forest Reserve, Southern Nigeria

AbstractThis study assessed changes in soil properties and soil fertility resulting from land‐use conversion from rainforest to oil palm and rubber plantations in Okomu Forest Reserve, Southern Nigeria. We collected 315 soil samples at 0–15, 15–30, and 30–60 cm and analyzed soil physicochemical properties. In addition, soil fertility index (SFI) was computed using the analytical hierarchical process. Our results showed that soil organic carbon declined by 40% and 60% (0–15 cm), 32% and 57% (15–30 cm) and 33% and 57% (30–60 cm) in oil palm and rubber plantations, respectively. Similarly, total nitrogen also declined by 43% and 56% (0–15 cm), 34% and 36% (15–30 cm), and 36% and 41% (30–60 cm) in oil palm and rubber plantations and was significantly lower in plantation soil than in the rainforest soil. Soil organic carbon and total nitrogen were, however, higher under oil palm than rubber plantations. In contrast, available phosphorus was higher under rubber plantations than oil palm plantations. The mean values of soil exchangeable potassium and sodium are significantly lower in the rainforest samples. Generally, SFI ranged from 7.30 to 20.46 in the rainforest, 4.16–13.21 in oil palm and 5.15–8.03 in rubber plantations. We conclude that soil degradation is more severe in oil palm plantations than in the rubber plantations. This implies that in addition to site‐specific management, species‐specific management strategy must also be developed to ensure sustainable utilization of soil resources in deforested rainforests.

Coconut-gliricidia mixed cropping systems improve soil nutrients in dry and wet regions of Sri Lanka

Agroforestry systems are alternative solutions for production and management of agricultural systems which may improve soil quality. In this study, we evaluated the potential of coconut Cocos nucifera-based Gliricidia (Gliricidia sepium) systems to improve soil quality of coconut lands in Sri Lanka in dry and wet regions. A three-year field experiment was conducted in a randomized complete block design with three treatments T0, T5 and T20, being respectively the control, five and twenty years aged Gliricidia intercropped coconut-based mixed systems. Three replicates of soil samples were taken at 0–15, 15–30 and 30–45 cm and differences in soil physical and chemical properties were evaluated among treatments and sites. We found significant effects of mixed system treatments on the soil chemical properties. In particular, organic matter, soil exchangeable potassium, total nitrogen and available phosphorus contents showed higher values in most coconut-gliricidia mixed systems’ soils, with highest values obtained for T20. Cumulatively for all soil depths, organic matter content (22%) and available phosphorus content (20%) were higher on the wet site, and total exchangeable potassium content (69%) higher on the dry site for T20. The pH, bulk density, microbial respiration and electric conductivity did not vary among treatments, but were influenced by the site characteristics, with the dry site showing higher values for pH and the wet site showing higher values for bulk density (5%), microbial respiration (33%) and electric conductivity (2%) in T20 treatment. The study demonstrates that the systems with Gliricidia differed in their soil chemical attributes and had higher levels of soil nutrients when compared to coconut monocrop even at early ages, underlying the potential of Gliricidia for the rehabilitation of coconut growing soils.

The effect of mineral fertilizers on the seasonal dynamics of exchangeable potassium in the orchard soil and the potassium status of sour cherry trees

The study was conducted to assess the impact of mineral fertilizers applied to the soil on the potassium level in the components of the “soil-plant” system of the sour cherry orchard. The experiment was conducted in the forest-steppe zone of the Central Russian Upland (Orel region) on loamy Haplic Luvisol during 2018-2020. The seasonal dynamics of exchangeable potassiumin the soil, the potassium status and productivity of sour cherry trees cv. ‘Turgenevka’ on the rootstock V-2-180 were studied in the orchard of 2015 planting. Fertilizers in the form of (NH2)2CO and K2SO4 were applied annually in early spring in doses of N30K40, N60K80, N90K120 and N120K160. It was found that a significant decrease in the level of potassium in the soil occurred during the period of intensive growth and crop formation, or after heavy precipitation. The use of fertilizers increased the content of exchangeable potassium in the soil (by 1.2-2.2 times), while the features of the potassium dynamics observed in unfertilized plots were preserved. Fertilizers contributed to the annual improvement of the potassium status of the leaves (by 0.05-0.24 % DW). The positive effect of fertilizers on the potassium content in fruits and the productivity of trees was manifested only in a year with prolonged intense precipitation (2020). The potassium content in fruits was 1.12-1.16 times higher than the control when applying N30K40, N60K80 and N90K120. A significant increase of tree productivity was found when applying N60K80 and N120K160 (by 54 and 69%, respectively).

Recycling rubberwood bark wastes into biochar to enhance chemical properties of peat soils

Peat soils in Malaysia is renowned for its poor chemical properties and often lead to restriction in agricultural uses. The abundance of waste in particle board and furniture industry offers a potential for producing biochar products with ability to enhance peat soil chemical properties. This study intends to evaluate the effects of different rate of rubberwood bark biochar on selected chemical properties of peat soils and growth performance of paddy variety MRIA 1, as a test crop. Results showed that application of rubberwood bark biochar at the rate of 226.80 grams (Treatment 3) significantly improve the soil pH, soil exchangeable potassium (K), calcium (Ca)and magnesium (Mg) combined with positive increment of tillers number, root length and height of paddy plant compare to other treatments. This study suggested a positive potential of rubberwood bark biochar to enhance the chemical properties of peat soils which led to good plant growth performance

Long-term effect of integrated fertilization on maize yield and soil fertility in a calcaric fluvisol

ABSTRACT In an 8-year study, the influence of integrated fertilization (combination of organic and inorganic fertilizers) on maize (Zea mays L.) yield and nutrition, with respect to nitrogen, phosphorus and potassium, at the different growth stages, was investigated in Quzhou County of the North China Plain. Three treatments were chosen for this study: inorganic fertilizers without organic fertilizers (IF), inorganic fertilizers plus low organic fertilizers (LOF) and inorganic fertilizers plus high organic fertilizers (HOF). The results showed that integrated fertilization significantly improved maize grain yield; the magnitude of increase in maize grain yield with HOF and LOF was 1.52 and 0.74 t ha−1, respectively, over the IF (9.20 t ha−1). The total plant biomass and uptake of nitrogen, phosphorus and potassium in maize plants across growing stages were significantly improved with integrated fertilization. The integrated supply of nutrients was also beneficial in improving soil organic carbon, total nitrogen, available phosphorus and exchangeable potassium over the years. The result suggests that nutrient management practices for maize cultivation in the North China Plain should preferably include the integrated use of organic and inorganic fertilizers (3.75 t ha−1 organic fertilizers supplemented with 125 kg N ha−1) to increase soil fertility and maize yield.