Distribution Of Soil Nutrients Research Articles

Distribution of Soil Chemical Properties of Smallholder Farms on Derelict Mined-Sites of Jos South LGA, Jos Plateau, Nigeria

Tin mining environments have constituted a degrading challenge to smallholder farmers whose lands have been overtaken. Attempts by smallholder farmers to restore the lands to farming are faced with soil productivity constraints. Yet, these farmers struggle to cultivate farms in-between the mined lands to meet up with subsistence food requirements. To date, the farmers have identified areas with low and high potentials due to years of continuous cultivation. This study was conducted in an environment that had undergone mining on a larger scale and is now undergoing surface mining on a small scale. Thirty-one (31) soil samples were taken at a depth of 0-20cm to investigate the spread of soil chemical properties on smallholder farms. Coordinates of the samples were acquired using GPS to create georeferenced continuous surfaces. The results indicated that the majority of the soil's chemical properties varied moderately. Organic matter (0.89-1.74%) and nitrogen (0.045 - 0.096%) needed mostly by crops were very low due to uninformed distribution of soil chemical properties. Geostatistics was used to generate continuous surfaces through Kriging. The small nugget effect showed spatial continuity between the neighboring points. Strong spatial dependence occurred for all soil nutrients tested, due to intrinsic soil properties such as soil parent material, topography, texture, and mineralogy. Generally, the spread of soil nutrients on the smallholder farm coincides with the smallholder farmers' identified potential areas. The study suggests that for proper nutrient interventions on the farms, distribution of soil nutrients on the farms should be done to avoid excesses and shortages of inorganic and organic interventions.

Spatial Distribution Characteristics of Soil Carbon and Nitrogen in Citrus Orchards on the Slope of Purple Soil Hilly Area

Since the 1990s, a large area of sloping farmland in a purple soil hilly region of southwest China was converted into an orchard to prevent soil erosion, increase soil fertility, and elevate economic benefits for farmers. In order to explore the spatial distribution of soil carbon (C) and nitrogen (N) fractions on the slope of returning arable lands to citrus orchards in purple soil hilly areas, a soil sampling event was carried out in a citrus orchard at the Yanting Agro-ecological Experimental Station of Purple Soil, Chinese Academy of Sciences, to examine the differences in soil C and N fractions and their influencing factors. The results showed that the slope position had significant effects on the contents of soil total nitrogen (TN), nitrate nitrogen (NO3--N), and dissolved organic carbon (DOC) (P < 0.05), but the effects were not obvious regarding the total organic carbon (SOC) and ammonia nitrogen (NH4+-N) of the soil (P > 0.05). For topsoil (0-30 cm), the variation trend of soil NO3--N content along the slope was upper slope < middle slope < lower slope, whereas the TN and DOC contents along the slope exhibited the trend of upper slope > middle slope > lower slope. The contents of soil C and N in each slope position generally showed a downward trend with increasing soil depth (0-30 cm). The contents of soil TN, SOC, NO3--N, and DOC were significantly affected by soil depth (P < 0.05). The TN storage (0-30 cm) significantly decreased from the top to the bottom within the soil slope, with a value of 2.37, 1.89, and 1.62 t·hm-2 (reported as N) for the upper slope, middle slope, and lower slope, respectively. There was no significant difference in SOC reserves along the slope, with a range from 56.12 to 58.48 t·hm-2 (reported as C). Our results provide scientific basis for understanding the spatial distribution of soil nutrients of the restored farmland in purple soil hilly areas. Our research suggests that the spatial distribution of soil carbon and nitrogen storage should not be ignored when predicting the response of soil nutrients to land use change.

Predation and Biophysical Context Control Long-Term Carcass Nutrient Inputs in an Andean Ecosystem

Animal carcass decomposition is an often-overlooked component of nutrient cycles. The importance of carcass decomposition for increasing nutrient availability has been demonstrated in several ecosystems, but impacts in arid lands are poorly understood. In a protected high desert landscape in Argentina, puma predation of vicuñas is a main driver of carcass distribution. Here, we sampled puma kill sites across three habitats (plains, canyons, and meadows) to evaluate the impacts of vicuña carcass and stomach decomposition on soil and plant nutrients up to 5 years after carcass deposition. Soil beneath both carcasses and stomachs had significantly higher soil nutrient content than adjacent reference sites in arid, nutrient-poor plains and canyons, but not in moist, nutrient-rich meadows. Stomachs had greater effects on soil nutrients than carcasses. However, we did not detect higher plant N concentrations at kill sites. The biogeochemical effects of puma kills persisted for several years and increased over time, indicating that kills do not create ephemeral nutrient pulses, but can have lasting effects on the distribution of soil nutrients. Comparison to broader spatial patterns of predation risk reveals that puma predation of vicuñas is more likely in nutrient-rich sites, but carcasses have the greatest effects on soil nutrients in nutrient-poor environments, such that carcasses increase localized heterogeneity by generating nutrient hotspots in less productive environments. Predation and carcass decomposition may thus be important overlooked factors influencing ecosystem functioning in arid environments.

Spatial differentiation of soil nutrients and their ecological chemometrics based on geographic detector in National Agricultural Park of Tangchang, Southwest China.

In order to analyze the spatial variability of soil nutrients and their ecological chemometrics in Tangchang Town, National Agricultural Park, 20 influencing factors were selected: soil pH, Cd, Hg, As, Cu, Pb, Cr, Zn, Ni, Se, elevation, slope, aspect, land use type, distance from industrial land, distance from commercial land, distance from railway, distance from residential area, distance from highway and distance from river. The effects of various influencing factors on the spatial variability of total organic carbon (TOC), total nitrogen (N), total phosphorus (P), total potassium (K) and ecological stoichiometry were analyzed by means of geographic detector. The results showed that average contents of soil TOC, N, P and K in the study area are 10.24 g kg-1, 1.33 g kg-1, 1.14 g kg-1 and 23.60 g kg-1, respectively, and there were significant differences in the spatial distribution of soil nutrients and their eco-stoichiometry in the study area, and TOC, N, P, K, C/N, C/P, C/K, N/P, N/K and P/K has a significant correlation with each other and most correlation coefficients are above 0.5 or below -0.5. Factor detection showed that soil properties, distance from railway and distance from residential area had the most significant explanatory power to the spatial heterogeneity of soil nutrients and eco-stoichiometry. Interaction detection showed that the interaction between soil properties with other factors was the most important factor affecting the spatial differentiation of soil nutrients and their ecological chemometrics, and elevation, distance from railway and distance from residential area were also important factors. Risk detection showed that the differences of soil nutrients and their ecological stoichiometry were most significant in the subregions of soil properties (pH, Cd, Hg, As, Cu, Pb, Cr, Zn, Ni and Se).

The Median Isn’t the Message: soil nutrient hot spots have a disproportionate influence on biogeochemical structure across years, seasons, and depths

Soil nutrient distribution is heterogeneous in space and time, potentially altering nutrient acquisition by trees and microorganisms. Ecologists have distinguished “hot spots” (HSs) as areas with enhanced and sustained rates of nutrient fluxes relative to the surrounding soil matrix. We evaluated the spatial and temporal patterns in nutrient flux HSs in two mixed-conifer forest soils by repeatedly sampling the soil solution at the same spatial locations (horizontally and vertically) over multiple seasons and years using ion exchange resins incubated in situ. The climate of these forests is Mediterranean, with intense fall rains occurring following summers with little precipitation, and highly variable winter snowfall. Hot spots formed most often for NO3− and Na+. Although nutrient HSs often occurred in the same spatial location multiple times, HSs persisted more often for PO43− NH4+, and NO3−, and were more transient for Ca2+, Mg2+, and Na+. Sampling year (annual precipitation ranged from 558 to 1223 mm) impacted the occurrence of HSs for most nutrients, but season was only significant for PO43−, NH4+, NO3−, and Na+, with HSs forming more often after fall rains than after spring snowmelt. The frequency of HSs significantly decreased with soil depth for all nutrients, forming most commonly immediately below the surficial organic horizon. Although HSs accounted for less than 17% of the sampling volume, they were responsible for 56–88% of PO43−, NH4+, and NO3− resin fluxes. Our results suggest that macronutrient HSs have a disproportional contribution to soil biogeochemical structure, with implications for vegetation nutrient acquisition strategies and biogeochemical models.Graphical abstract

Variations in soil physico-chemical properties, soil stocks, and soil stoichiometry under different soil layers, the major forest region Liupan Mountains of Northwest China.

Liupan Mountains are an important region in China in the context of forest cover and vegetation due to huge afforestation and plantation practices, which brought changes in soil physio-chemical properties, soil stocks, and soil stoichiometries are rarely been understood. The study aims to explore the distribution of soil nutrients at 1-m soil depth in the plantation forest region. The soil samples at five depth increments (0-20, 20-40, 40-60, 60-80, and 80-100 cm) were collected and analyzed for different soil physio-chemical characteristics. The results showed a significant variation in soil bulk density (BD), soil porosity, pH, cation exchange capacity (CEC), and electric conductivity (EC) values. More soil BD (1.41 g cm-3) and pH (6.97) were noticed in the deep soil layer (80-100 cm), while the highest values of porosity (60.6%), EC (0.09 mS cm-1), and CEC (32.9 c mol kg-1) were reflected in the uppermost soil layer (0-20 cm). Similarly, the highest contents of soil organic carbon (SOC), total phosphorus (TP), available phosphorus (AP), total nitrogen (TN), and available potassium (AK) were calculated in the surface soil layer (0-20 cm). With increasing soil depth increment a decreasing trend in the SOC and other nutrient concentration were found, whereas the soil total potassium (TK) produced a negative correlation with soil layer depth. The entire results produced the distribution of SOCs and TNs (stocks) at various soil depths in forestland patterns were 0→20cm > 20→40cm > 40→60cm ≥ 60→80cm ≥ 80→100 cm. Furthermore, the stoichiometric ratios of C, N, and P, the C/P, and N/P ratios showed maximum values (66.49 and 5.46) in 0-20 cm and lowest values (23.78 and 1.91) in 80-100 cm soil layer depth. Though the C/N ratio was statistically similar across the whole soil profile (0-100 cm). These results highlighted that the soil depth increments might largely be attributed to fluctuations in soil physio-chemical properties, soil stocks, and soil stoichiometries. Further study is needed to draw more conclusions on nutrient dynamics, soil stocks, and soil stoichiometry in these forests.

A mosaic pattern of apple orchards and farmland affects the distribution of soil water and nutrients in their adjacent areas on the Chinese Loess Plateau

With the vigorous promotion of apple tree planting on the Chinese Loess Plateau (CLP), a mosaic pattern of apple orchards and traditional farmland has emerged in the region. However, the interaction between adjacent farmland and apple orchards in terms of soil water and nutrient migration remains unclear. This study aimed to investigate the spatial distribution of the soil water content (SWC) and soil nutrients, as well as their interactions, in 0–10 m soil layers of apple orchards of different stand ages and adjacent farmland under the orchard-farmland land use pattern. The results revealed a significant decrease in average-depth SWC in the orchards in the 0–10 m soil profile (R2 = 0.90) with increasing orchard age, accompanied by a significant increase in soil water deficit (SWD, R2 = 0.94). The annual growth rate of SWD was found to be as high as 5.94 mm·m−1·y−1. Deep soil and surrounding farmland were identified as important sources of soil water for apple tree growth, particularly in older orchards; a 25-year-old orchard absorbed approximately 10.8 % of soil water towards farmland with a horizontal distance of 7 m. The distribution of soil organic carbon (SOC) and total nitrogen (TN) in the 0–10 m soil profile exhibited a similar pattern, decreasing and then stabilizing with increasing depth. However, the peak depth and accumulation of soil nitrate (NO3–-N) significantly increased with orchard age. The migration and accumulation of NO3–-N in the soil provided a scientific basis for the transport of soil water, with NO3–-N accumulation (405.32 mg kg−1) observed in the deep soil (3–6 m) of farmland located 5 m away from a 30-year-old orchard, confirming the exchange of soil water and nutrients between the orchard and the farmland. The stand age of the orchards was identified as the main environmental factor influencing soil water transport under the orchard-farmland land use pattern. Overall, our findings provide valuable insights into the interaction between apple orchards and farmland under the mosaic pattern, which can contribute to a more rational layout of apple orchards and farmland in the future, promoting the efficient utilization of soil water and nutrients on the CLP.

Investigation into the Effects of Different Restoration Techniques on the Soil Nutrient Status in Degraded Stipa grandis Grassland

The degradation and desertification of grassland ecosystems have garnered significant attention both domestically and internationally. Grassland restoration techniques are widely considered a principal measure to promote the sustainable utilization of grasslands, with soil nutrient content being a core indicator for assessing the effectiveness of restoration in degraded grasslands. This study aims to explore the differential impacts of various grassland restoration methods on soil nutrient distribution in degraded Stipa grandis grasslands. Three major restoration methods, i.e., root cutting, enclosure, and fertilization, were applied in the study area. The soil nutrient content was measured and analyzed under the different restoration methods and at varying depths. The results revealed that under all three restoration methods and at different soil depths (0–10 cm, 10–20 cm, 20–30 cm), the organic matter, total nitrogen, total phosphorus, alkali-hydrolyzable nitrogen, alkali-hydrolyzable phosphorus, and available potassium contents were significantly higher than those in the control group (p < 0.05). Furthermore, as soil depth increased, the contents of organic matter and all nutrients gradually decreased. Specifically, regarding the contents of different nutrients, the order of organic matter, total nitrogen, total phosphorus, alkali-hydrolyzable nitrogen, and available phosphorus was as follows: fertilization > enclosure > root cutting > control, while the contents of total potassium and available potassium followed the sequence: fertilization > enclosure > control > root cutting. Additionally, based on the canonical correlation analysis (R2 = 0.88), the total phosphorus content in soil had the greatest impact on soil nutrients, while vegetation cover and plant height contributed the most to vegetation characteristics. In grassland restoration, the increase in soil total phosphorus led to higher vegetation cover and height, mildly influenced plant diversity and density, and simultaneously promoted biomass accumulation. These research findings provide a solid theoretical foundation for the application of grassland restoration techniques, contributing to the sustainable development of grassland ecosystems.

Vertical Distribution of Available Plant Nutrients in Soils of Mid-Central Tableland Agro-climatic Zone of Odisha, India

Study on the vertical distribution of plant nutrients is very essential for improving crop production and productivity rather than studying the nutrient characteristics of the surface soil only. It is because many plants absorb nutrients from the subsoil. Moreover, the vertical distribution of nutrients is much more complex because of the many simultaneous processes going on in the soils such as recycling of the plant residues, leaching of nutrients, and weathering of parent materials. In this context, two pedons located in pedons in two different land types(upland and low land) of Dhenkanal district of the Mid-Central Tableland argo-climatic zone of Odisha were selected for studying the depth-wise vertical distribution of plant nutrients. Genetic horizon-wise soil samples were collected, processed, and analyzed for different soil properties viz., textural class (sand, silt, clay), pH, electrical conductivity (EC), soil organic carbon (SOC), available nitrogen (N), phosphorus (P), potassium (K), sulfur (S) and boron (B) content. The results indicated that there was a gradual decrease in the concentration of SOC, available N, P and S with soil depth. Whereas soil reaction (pH), EC and available K content increased with soil depth. Therefore, surface soils were observed to be more fertile but acidic, whereas the sub-soils were of higher pH. The findings of this study will be helpful for the scientific as well as the farming community for suggesting and uptaking suitable crop and land use plans for sustainable agricultural and land use management.

Coupling effects of phosphate fertilizer type and drip fertigation strategy on soil nutrient distribution, maize yield and nutrient uptake

Fertigation strategy has been shown to impact nitrogen distribution in drip irrigation, but it remains unclear whether it would impose a comparable effect on phosphorus migration in phosphorus fertigation. A two-year field experiment was conducted to evaluate the effects of different phosphorus sources (mono-ammonium phosphate (MAP) and ammonium polyphosphate (APP)) and four fertigation strategies with varying sequences and durations of water irrigation and fertilization in the irrigation cycle (i.e., applying the fertilizer for the full irrigation cycle, 1/4 W-1/2 F-1/4 W (first applying water (W) for one-fourth of the total irrigation time, then applying fertilizer solution (F) for one-half of the total irrigation time, followed by applying water (W) for the remaining irrigation time, 1/2 W-1/2 F, and 1/2 F-1/2 W) on soil nutrient distribution, maize yield, and nutrient use efficiency. The results indicated that advancing the fertilization period within an irrigation cycle favored nitrogen and phosphorus migration, especially in the 10–40 cm soil layer. APP enhanced soil phosphorus mobility and availability compared to MAP under a given fertigation strategy, particularly during the maize filling stage. The combined performance of fertigation strategies and phosphorus sources varied in terms of soil nutrient distribution and nutrient uptake. MAP is more suitable for fertigation strategies with more post-fertilization irrigation water. For simultaneous fertigation with nitrogen and phosphate fertilizers, it is recommended to apply nitrogen and weakly adsorbed phosphate fertilizers during the middle of the irrigation cycle, while strongly adsorbed phosphate fertilizers occur earlier, along with appropriately extending the duration of post-fertilization water application.

Impact of Crude Oil Contamination on Soil Physicochemical Properties around the Sildubi Oil Spill, Borhola, Assam

Crude oil contamination can affect the soil physicochemical properties and it is a serious constraint on the rice ecosystem near the oil drilling sites. The objective of this study was to identify the effects of crude oil contamination through oil exploration on soil health and the horizontal distribution of soil nutrients in rice field soils in the Sildubi area, Jorhat district, Assam. Soil samples were collected at a depth of 0–15 cm from the drilling site and from the four directions (East, West, South and North) in a circular mode with a radius of 500 and 1000m away from the oil spill. Each sample was mounded with four replications. Samples were analyzed for physicochemical properties by using standard methods that reflect soil nutrient status.
 The percentage of organic carbon, organic matter and soil pH are found to be higher at the drilling site compared to the results obtained in the rice field soils, apart by 500 and 1000m from the central zone. Similarly, bulk density, moisture percentage and electrical conductivity were found to be lowest in the soils of the drilling site. In our study, considerable variation in the horizontal distribution of soil nutrients was also observed. The highest P, Ca and nitrogen contents were recorded in the oil-contaminated soils compared to soils collected from 500 and 1000m radius. The total soil Fe was significantly higher in the samples collected at 1000m. Spilled crude oil is certainly responsible for alterations in soil physicochemical properties and the horizontal distribution of some plant-specific nutrients. High concentrations of Fe and P observed due to crude oil contamination have been developing Fe stress situations reducing crop production in nearby agricultural lands.

Biochar alleviates the crop failure of rice production induced by low-nitrogen cultivation mode by regulating the soil microbes taxa composition.

To improve the nitrogen utilization efficiency and a series of environmental problems caused by excessive application of nitrogen fertilizer, actual agricultural production often reduced the usage ratio of nitrogen fertilizer. However, the reduction in nitrogen fertilizer not only affects the soil microenvironment but also leads to adverse effects on rice yield. Due to its unique properties, biochar can regulate soil nutrient distribution and significantly affect soil microbial community structure/functions. To further understand the effects of different levels of biochar on soil nutrient indicators, soil microorganisms and crop growth under the nitrogen-reduction condition, our experiment with four groups was set up as followed: 0%, 2.5% and 5% biochar application rates with 99kg/hm2 nitrogen fertilizer and one control group (the actual fertilizer standard used in the field:110kg/hm2) without no exogenous biochar supplement. The rice yield and soil nutrient indexes were observed, and the differences between groups were analyzed based on multiple comparisons. 16S ribosomal RNA and ITS sequencing were used to analyze the community structure of soil bacteria and fungi. Redundancy analysis was performed to obtain the correlation relationships between microbial community marker species, soil nutrient indexes, and rice yield. Path analysis was used to determine the mechanism by which soil nutrient indexes affect rice yield. The results showed that a higher application rate of biochar led to a significant increased trend in the soil pH, organic matter and total nitrogen content. In addition, a high concentration of biochar under nitrogen-reduction condition decreased the soil bacterial diversity but elevated the fungal diversity. Different concentrations of biochar resulted in these changes in the relative abundance of soil bacteria/fungi but did not alter the dominant species taxa. Taken together, appropriate usage for biochar under the nitrogen-reduction background could induce alteration in soil nutrient indicators, microbial communities and crop yields. These results provide a theoretical basis for exploring scientific, green and efficient fertilization strategies in the rice cultivation industry. Notably, the interaction relationship between rhizosphere microorganisms in rice and soil microbial taxa are not yet clear, so further research on its detailed effects on rice production is needed. In addition, the Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis for the physiological functions of the soil microbes could only predict the potential metabolic pathways. Therefore, the next-generation metagenome techonology might be performed to explore detailed metabolic differences and accurate taxa alteration at the "species" level.

Soil Moisture, Nutrients, Root Distribution, and Crop Combination Benefits at Different Water and Fertilizer Levels during the Crop Replacement Period in an Apple Intercropping System

Uneven soil moisture and nutrient distribution before and after intercropping limits apple cropping system productivity in the western Shanxi–Loess Plateau area. To address this issue, a field trial was conducted between 2020 and 2021 to study the effects of different water and fertilizer management practices on soil moisture, nutrients, and root distribution, as well as the overall effectiveness of the apple–maize and apple–soybean intercropping systems during crop replacement. The experiment involved two irrigation methods: drip (D) and flood (M) irrigation. Three irrigation levels included rain-fed without irrigation (W0), and 50% (W1) and 80% (W2) of field capacity (Fc). Three fertilizer treatments included no additional fertilizer application (F0), 375 kg∙hm−2 (F1), and 750 kg∙hm−2 (F2), in addition to a control (CK) without irrigation or fertilization. The soil water content (SWC) decreased after the crop replacement. Additionally, nitrate nitrogen (NN), ammonium nitrogen (AN), and organic matter (OM) content levels in all treatments increased, whereas total phosphorus (TP) content decreased. The soil layer with crop roots moved downward after crop replacement, and partial fertilizer productivity (PFP), irrigation water use efficiency (IWUE), and water use efficiency (WUE) were decreased under both irrigation treatments. Principal component analysis showed that the W2F2 treatment had the highest benefit from crop combination across both irrigation treatments during the crop replacement period. According to our results, to optimize the benefits of apple-crop intercropping, drip irrigation with complete water supply and flood irrigation with incomplete water supply are recommended during crop replacement. In addition, an upper irrigation limit of 80% Fc with 750 kg∙hm−2 fertilization is recommended for optimal water and fertilizer regulation.

Biochar improves soil properties and corn productivity under drought conditions in South Korea

Biochar has been shown to improve soil properties and plant productivity in soils with inherently low fertility. However, little has been reported for upland corns under dry and wet precipitation regimes. This study investigates the effect of biochar addition on a range of soil physicochemical, biological, and hydrological properties, and corn growth and productivity under agrometeorological drought and wet conditions. Here, experiments were laid out in a randomized complete block design with three replications at two sites during 2017 and 2018 in South Korea. Treatments included (i) CN: control (ii) IF: inorganic fertilizer (N–P–K) at 145–30–60 kg ha−1; (iii) BS: barley straw at 5 t ha−1; (iv) CWBC: corn waste biochar at 5 t ha−1; (v) CWBC + IF: corn waste biochar + inorganic fertilizer; (vi) CWBC + BS: corn waste biochar + barley straw. The year 2017 was relatively dry, whereas the year 2018 was wet. Despite drought conditions in the year 2017, biochar facilitated soil water conservation. However, higher precipitation in 2018 increased the quantity and distribution of soil water and nutrients in the top 15 cm. Biochar reduced soil bulk density, and increased porosity, cation exchange capacity and total organic carbon in both years but increased total bacterial counts during the dry year only. Bacterial population was generally higher under wet conditions. Similarly, more soil CO2 was emitted in the wet year than in the dry year. Results further indicated that biochar can enhance corn biomass and grain yield regardless of precipitation conditions. The grain index was, however, affected by rainfall and was significantly different across treatments in the year 2018 only. All biomass, grain yield, and grain index were highest in CWBC + IF treatment and lowest under CN treatment. Indeed, biochar addition appeared to improve soil quality and soil conditioning effects in the drought and wet years, ameliorating soil and plant properties. Overall, biochar can improve water and nutrients storage, availability, and uptake, and therefore corn productivity during hydrological extremes.Graphical abstract

County-Scale Spatial Distribution of Soil Nutrients and Driving Factors in Semiarid Loess Plateau Farmland, China

Characterized by a topography of thousands of ravines, the Loess Plateau has highly complex spatial variability in terms of soil nutrients. Therefore, it is of considerable importance to study the soil nutrient spatial distribution, driving factors of precise fertilizer management, and the strategic use of soil nutrient resources. In 2017, 242 soil samples were taken from the semiarid Anding district farming region in northern China. The spatial variability and factors influencing soil nutrients were studied using statistical and geostatistical methods. The results showed that the mean soil organic matter (SOM), total nitrogen (TN), available phosphorus (AP), available potassium (AK), and pH values were averaged at 12.64 g·kg−1, 0.84 g·kg−1, 23.20 mg·kg−1, 188.87 mg·kg−1, and 8.60, respectively. The nugget-to-sill ratios for the semi-variograms of SOM, TN, AP, and AK varied from 25.84 to 49.93%, while the coefficients of variation varied from 24.53 to 69.44%, revealing that all four indicators exhibited considerable variability, and that the samples’ geographical variability was produced by a combination of random and structural factors. Overall increasing trends were exhibited from the middle to the northeast and southwest in the distributions of SOM, TN, and AP. The spatial distribution of AK displayed the opposite trend, increasing from the southwest to north and southeast. The texture of the tillage layer was the main factor directly affecting SOM, and explained 8% of its variation. The distribution of TN was mainly influenced by the irrigation method and water source type. AP and AK contents differed significantly between the two parent materials, three textures, and three topography types at the level of p < 0.01. In conclusion, the regional soil fertility was poor, spatial heterogeneity was moderate, and influencing factors were complex, highlighting the need to adopt precise fertilization management and adopting land management measures according to the actual influencing factors of each nutrient, thereby contributing to the enhancement of regional fertility.

Restoring soil nutrient stocks using local inputs, tillage and sorghum-green gram intercropping strategies for drylands in Eastern Kenya

Soil macronutrient and micronutrient availability is particularly critical in semi-arid agro-ecological zones that are characterized by poor soil fertility and low rainfall regimes. An experiment was initiated in Siakago, Embu County to investigate the effects of tied-ridges, conventional tillage and input applications on soil nutrient fertility using a randomized complete block design with a split-split plot arrangement for 4 seasons (2018–2021). The treatments comprised of two main plot tillage systems, three cropping systems allocated to the sub-plots and four soil input management treatments assigned to sub-sub plots. ANOVA was used to test the effects of different treatments including tillage, crop system and soil fertility management using Genstat software. The data was also subjected to Principal Component Analysis procedures using R ("FactoMineR" and "factoextra") to examine the inter-relationship patterns between different soil fertility parameters and to reduce the data into independent soil fertility components. There were significant main effects due to crop system (Soil Mn), tillage and crop system interaction (SOC and TSN) and soil fertility management (TOC, TSN, Ca, Zn). Soil inputs significantly influenced soil carbon concentrations (p = 0.002), with the lowest values observed in the control (0.2 %), followed by sole fertilizer (0.35 %), manure + fertilizer (0.41 %) and the fully decomposed manure treatment (0.61 %). The soil-extracted manganese values recorded significant effects due to crop system, while soil-extracted Zn values were significant due to soil fertility management. Multivariate analysis results revealed the structure of soil nutrient distribution. Tied ridging can improve soil micronutrient availability through reduced soil erosion, conservation of soil organic matter, which can improve soil micronutrient availability. Soil conservation practices such as tied-ridging integrated with organic input applications can enhance multiple nutrient availability for improved crop performance and human nutrition in dryland farming systems where farmers lack soil moisture, technologies and resources to enhance crop nutrient availability.

Effect of land use on carbon-, nitrogen- and silica soil stocks in the South African bushveld

Anthropogenic land use alters soil properties and influences biological transformations in the root zone, thereby affecting the distribution and supply of soil nutrients. It is generally acknowledged that human land-use activities such as intensive cattle farming and cultivation of citrus products lead to a homogenization of soil nutrients. This research aims at investigating the heterogeneity in soil nutrient stocks and BSi stocks (a beneficial plant element) within the Savannah biome of South Africa. In this study, C-N-Si stocks and their ratios were quantified in the soil of five different land use types, common in South Africa. The five different land use types are i) bush savannahs, ii) mopane-dominated woodlands, iii) annually burned land, iv) communal grazing land and v) citrus orchards. Empirical research however could not fully validate this hypothesis. In particular fire management and game farming (natural land use type) led to more variability in nutrient pools, with occasional occurrences of C-N-Si hotspots. Our results suggest that when ecosystem analysis of soil nutrient and carbon stocks is handled as a homogeneous unit potentially large mistakes are made, even in anthropogenic landscapes previously hypothesized with uniform nutrient distributions.

Effects of Soil Properties and Nutrients on the Fruit Economic Parameters and Oil Nutrient Contents of Camellia oleifera

The Camellia oleifera industry is hindered by the substandard quality of its fruits and the low yield of camellia seed oil. Although soil factors have been shown to affect the productivity of this plant, the relationship between C. oleifera characteristics and soil properties and nutrients remains unclear. Therefore, we investigated soil factors within the central distribution area of this species. Our findings revealed that this plant thrives in acidic soils with a medium cation exchange capacity. There were moderate differences in the main and medium element contents in the soils, while the variation of microelements was significant. Overall, C. oleifera cultivated soils were poor, with an uneven distribution of soil nutrients. Most of the shape characteristics of camellia fruits showed moderate variability, whereas dry kernel rate and oil content exhibited minor variability. The fatty acid profiles remained stable across different planting sites, but there were higher variations in the content of active compounds. Fruit shape characteristics were primarily influenced by soil properties, while soil nutrients mainly affected the seeds and kernels of the fruit. Minor fatty acid content could be influenced by soil properties and nutrients, except for total nitrogen (TN), which specifically affected the content of palmitic acid and oleic acid. There was no significant correlation between soil factors and sterols, polyphenols, and tocopherols, while squalene was affected by soil properties. Our study highlights the importance of considering soil properties and nutrients in the cultivation of C. oleifera and emphasizes the need for rational fertilizer application.

Spatial heterogeneity of soil organic carbon and soil nutrients and their controlling factors in a small watershed in Northeast China

AbstractUnderstanding the spatial distribution of soil organic carbon (SOC) and soil nutrients is crucial for optimizing land management in watersheds. This study explored the spatial distribution of SOC, total nitrogen (TN) and total phosphorus (TP) in topsoil (0–20 cm) at a hilly small watershed site in Northeast China, and identified the controlling factors. The Gaussian mixture model optimally described SOC and TN with the ratio of nugget to sill variance (C0/[C + C0]) indicating moderate spatial dependence for SOC (63.7%) and TN (59.3%). TP was best modelled by the spherical model and demonstrated weak spatial autocorrelation and strong human influence, with a nugget to sill variance of 0.841. Land use significantly affected SOC, TN and TP contents, with the highest values recorded in woodland, followed by farmland and shrubland. Soil properties including bulk density (BD), gravel content (GC), moisture content (MC), soil porosity (SP) and the mean weight diameter (MWD) of water‐stable aggregates significantly correlated with SOC and TN content, but not with TP. Redundancy analysis revealed that soil properties (BD, GC and SP), topography (slope and aspect) and gully erosion contributed 55.7%, 24.7% and 4.3% of the spatial variation in SOC, TN and TP, respectively. Hence, these are the dominant factors shaping the spatial variation of SOC and soil nutrients at the site. These results can aid the further development of optimized land management strategies.

Field Baseflow Eluting SOM-Rich Sandy Soil to Exacerbate Non-Point Source Pollution of Lake Erhai, Southwest China

Excessive nutrient loss from farmland located on the west bank of Erhai Lake has resulted in significant non-point source pollution within the Lake Erhai basin. However, mitigating this issue proves challenging due to the intricate nature of soil properties and environmental factors. Here, during the rainy season in the Lake Erhai basin, we collected and analyzed soil profile samples, 35 topsoil (0–20 cm) samples, and more than 300 field baseflow samples. Our objective was to explore the influences of soil properties, field baseflow, and agricultural management measures on the spatiotemporal migration of nutrients. The results indicated that the concentration of soil organic matter (SOM) has a significant impact on the spatial patterns of nutrient distribution in sandy soil. Consequently, this leads to a substantial reduction in the potential for nutrient loss in the Lake Erhai basin. The vegetable-field baseflow exhibited the highest concentrations of nitrogen and phosphorus when subjected to high fertilization and flood irrigation. The concentrations of TN and TP in baseflow increase by a factor of 2 and 7.7, respectively, during rainfall compared to periods of no rainfall. Optimizing agricultural measures, such as replacing chemical fertilizers with organic fertilizers and modifying irrigation methods to enhance the organic content of sandy soil and minimize baseflow elution, has a beneficial impact on mitigating agricultural non-point source pollution in the Erhai Lake basin. The research results can enable us to have a more systematic understanding of the problem of non-point source pollution in the Erhai River Basin, and provide a theoretical basis for developing targeted agricultural non-point source pollution mitigation plans. Simultaneously, optimizing agricultural management models to strike a balance between agricultural economic development and ecological protection issues holds significant practical significance for managers.