Extractable Nutrient Levels Research Articles

Soil Fertility Changes With Climate and Island Age in Galápagos: New Baseline Data for Sustainable Agricultural Management

While the extended absence of human influence has led to matchless natural conditions on the Galápagos archipelago, agricultural activities on the inhabited islands are increasingly affecting soil health and functioning. However, a systematic assessment of the agricultural soils on the Galápagos Islands is still absent. Plate tectonics and hotspot volcanism cause an eastward drift of the archipelago and result in a west-to-east soil age gradient from approx. 1 to 1,000 ka. In addition, precipitation regimes change from arid to humid with elevation on the higher-standing islands. The objective of this study was to investigate differences in soil fertility parameters and Mehlich (III)-extractable nutrient levels along these gradients in order to provide baseline information for sustainable agricultural management. Topsoil samples (0–20 cm) from 125 farms of the islands Isabela, Santa Cruz and San Cristóbal were analyzed. Gravel and sand content, pH, electrical conductivity, cation exchange capacity, base saturation, soil organic C and total N content tended to decrease with increasing island age, while clay content, soil macroaggregate stability, plant-available water and bulk density increased. Mehlich (III)-extractable base cations Ca, K, Mg and Na as well as P, Fe and Zn showed a decreasing tendency from the youngest to the oldest island, while Mn increased with island age. Mehlich (III)-extractable Cu and Na reached their highest levels on the most intensively farmed, intermediate-aged island Santa Cruz, likely related to anthropogenic inputs and irrigation with brackish water, respectively. Changes along the altitudinal climate gradient within the studied islands were most significant for soil pH, base saturation, and Mehlich (III)-extractable Ca and Mn. Our results highlight the importance of site-specific agricultural management to account for the strong heterogeneity in soil parameters among and within the Galápagos archipelago. The data provided herein shall serve as a baseline for targeted future management strategies to avoid soil degradation, restore and maintain soil functioning and, hence, sustain the soils’ provision of ecosystem services in this unique archipelago.

Soil Contamination Assessments from Drilling Fluids and Produced Water Using Combined Field and Laboratory Investigations: A Case Study of Arkansas, USA.

Rotary drilling for oil and natural gas uses drilling fluid for lubrication of the bit, to seal off unstable shale layers, and floating out rock cuttings. Drilling fluid is a water–clay chemical mixture. Produced water is a water–sand chemical mixture. Land farming is a common disposal technique of drilling fluid and produced water. In the land farming process, amendments of fluid are repeatedly applied to the soil surface. Plant growth and soil chemical properties may be altered by additions of drilling fluid, because of alkalinity, salinity, trace elements, and petroleum residue contained in waste. The objective of this study was to determine the change in soil pH, electrical conductivity (EC), total nitrogen and carbon, and extractable nutrient levels following the land application of drilling fluid and produced water. The study was a comparison of three plots with similar soil properties and conditions. The three study plots had various levels of drilling fluid and produced water applications. The data show a major difference from field-to-field for EC, Na, and Cl levels. The EC and salt levels increased with additional applications of drilling fluid and produced water. The percent total nitrogen values and plant available P levels were very low in all fields. High EC and salt values, coupled with low N and P levels, would be detrimental to plant growth and development. To successfully vegetate this land-farm site, application of N and P fertilizer would be required. This study help to give a better understanding of practical ways to land-farm drilling fluid and produced water in a fashion that both minimizes environmental issues and is economically feasible in Arkansas. Thus, this research will provide important information for soil contamination management and contributes on understanding of the responses of soil properties to drilling fluid and produced water in the future.

Calibration of Mehlich-3 with Bray P1 and Ammonium Acetate in the Tri-State Region of Ohio, Indiana and Michigan

ABSTRACT Field crop fertilizer recommendations for Ohio, Indiana and Michigan are currently based on the Bray P1 extractant for phosphorus (P) and the ammonium acetate extractant (AA) for base cations. The fertilizer recommendations in this Tri-State region are currently being revised and will use the Mehlich-3 soil test extractant as the new basis for P and potassium (K) fertilizer recommendations. The goal of this study was to document the relationships between Mehlich-3, Bray P1, and AA soil test extractants and to provide a comprehensive review of these relationships published in the literature. Soil samples (n = 2,659) were collected across Ohio and Indiana from a diverse range of fields and analyzed for Mehlich-3, Bray P1 and AA extractable nutrients for P, K, calcium (Ca), and magnesium (Mg). Mehlich-3 P values were highly related to, but 35% greater than Bray P1 values. Mehlich-3 values were highly related to AA values, but 14% greater than AA-K, 13% greater than AA-Ca and 20% greater than AA-Mg. Our results are largely consistent with a comprehensively compiled literature review that indicates Mehlich-3 is an efficient and suitable soil test extractant for assessing extractable nutrient levels in the Tri-State region of Ohio, Indiana and Michigan.

Path Analyses of Grain P, Zn, Cu, Fe, and Ni in a Biosolids-Amended Dryland Wheat Agroecosystem.

Land application of biosolids is an effective means of recycling plant nutrients and is the primary method of biosolids reuse endorsed by the USEPA. One issue concerning biosolids application is the extent of the contribution of biosolids-borne plant nutrients to the overall crop concentration and uptake or removal of these nutrients. We studied the effects of biosolids application on wheat ( L.) grain P, Zn, Cu, Fe, and Ni concentrations and uptake (removal) at two dryland agroecosystem sites from 1993 to 2014. We hypothesized that biosolids would have the greatest impact on wheat grain and uptake compared with ammonium bicarbonate-diethylenetriaminepentaacetic acid (AB-DTPA)-extractable nutrient levels, soil pH, or soil organic C concentrations. We used path analyses in combination with multiple linear regression to differentiate the direct, indirect, and total effects of cumulative biosolids applications, soil AB-DTPA, soil pH, and organic C. Biosolids rates, applied biennially from 1993 to 2014 at the beginning of a wheat-fallow rotation, were 0, 2.24, 4.48, 6.72, 8.96, and 11.2 Mg ha. None of the parameters had significant direct, indirect, or total effects on grain concentrations. Biosolids applications had the greatest positive direct impact compared with AB-DTPA levels, soil pH, or soil organic C on P, Zn, Fe, and Ni uptake (removal), whereas AB-DTPA had the greatest positive direct impact on Cu uptake. Soil AB-DTPA, pH, and organic C directly affected some grain concentrations and cumulative uptake, but no consistent trends were noted. This pathway approach allowed differentiation between causation and simple correlation for the effects of cumulative biosolids applications on wheat P, Zn, Cu, Fe, and Ni cumulative uptake but did not provide these same results for grain concentrations.

Soil properties related to the spatial pattern of microbial biomass and respiration in agroecosystems

Soil microorganisms exhibit a high degree of spatial variation, even in homogenously managed agroecosystems. The spatial pattern of microbial biomass and activity may be related to soil properties like hydrology, texture, organic matter and pH. This study took place in a 0.4-ha field with research plots under wheat and maize production. Soil microbial biomass, respiration and extractable nutrient levels were not generally affected by fertilizer treatments (inorganic NP fertilizer, poultry manure), relative to the unfertilized plots. This was probably due to soil heterogeneity; for instance, soil pH (1:2, soil:water) ranged from 5.8 to 7.2 across the field. Exploratory path analysis revealed that soil pH, dissolved organic carbon and total organic carbon concentrations were directly related to the spatial pattern in soil microbial biomass and respiration. This work demonstrates that path analysis could be used to identify independent soil variables and describe relationships between soil properties and microbial indicators in spatially heterogeneous agroecosystems. Key words: Field variability, microbial biomass, mineral fertilizer, organic amendment, soil respiration, spatial dependence

Sweetpotato Yield and Quality as Influenced by Cropping Systems

Producing safe and nutritious food for consumers and ensuring profitability and sustainability of farming enterprises through environmentally friendly agronomic practices are some of the major challenges facing agriculture today. Field studies were conducted in 2001 and 2002 to evaluate the effect of conventional (chemical-intensive) monocropping, transitional (reduced-synthetic input), and an organic (non-synthetic input) multiple cropping systems on sweet potato (Ipomoea batatas (L.) Lam) yield and quality, as well as soil properties. The studies were conducted on a Dexter silt loam soil in northern Mississippi. In both years No. I sweetpotato yield was greatest for the transitional and organic cropping systems and lowest for the conventional cropping system. In 2001, cropping system did not affect plant survival. In 2002, plant survival was greatest for the conventional cropping system and lowest for the organic cropping system. Soil extractable nutrient levels prior to planting (preplant soil fertility) were very high for Mg, high for P and Ca, medium for S, and low for K. Final post-harvest soil levels after the 2nd year: the content of Mg was very high for the three cropping systems, and high for P, K and Ca. Sulfur was high for the organic cropping system, and medium for the conventional and transitional cropping systems. In 2001, sweetpotato P content was greatest for the conventional cropping system and lowest for the transitional cropping system. Both Ca and Mg were greatest for the conventional cropping system but were not different from the transitional cropping system. Potassium was greatest for the organic cropping system and lowest for the transitional cropping system. Both N and S were not affected by cropping systems. In 2002, N content in roots was greatest for the conventional and organic cropping systems and lowest for the transitional cropping system. The other nutrients were not affected by cropping system. Sweetpotato roots under the conventional cropping system had the greatest protein, fat and ash contents, whereas crude fiber was the greatest for roots under the transitional cropping system. Root dry matter was greatest for the organic cropping system and lowest for the conventional cropping system. Data suggest that Beauregard sweetpotato cultivar can be successfully grown on a Delta silt loam soil in northern Mississippi. Where the production of No. 1 marketable sweetpotato roots are desired, both the transitional and organic cropping systems are recommended over the conventional cropping system. While the conventional cropping system will enhance root protein, fat and ash contents more than the transitional and organic cropping systems, both cropping systems will, respectively, enhance crude fiber and dry matter more than the conventional cropping system.

Comparison of various soil drying techniques on extractable nutrients

Abstract Changes that take place in soil samples as they are dried and stored may pose serious problems in predicting plant responses compared to moist soils under field conditions. The effects of drying and storage techniques (air, microwave, oven‐drying, and frozen) on the levels of Mehlich‐I‐extractable nutrients were evaluated in six diverse soils. The use of microwave‐drying as a rapid soil drying method prior to chemical analysis was also evaluated. Drying and freezing caused large changes in the levels of extractable nutrients in all soils. The effects of drying were dependent on drying intensity and the initial physical and chemical properties of the soil. Many of the changes in the levels of extractable nutrients resulting from drying the soil appear to be associated with the oxidation of organic matter (OM) and changes in hydration state and redox status of different soil components. Results from this study also indicate that microwave drying of soils has potential for rapid drying of soil sampl...

Effect of trickle fertigation with three forms of nitrogen on soil pH, levels of extractable nutrients below the emitter and plant growth

The effects of application of nitrogen as calcium nitrate, urea or ammonium sulphate at two rates through the trickle irrigation system on pH and nutrient status of the wetted volume of soil below the emitters and on growth and nutrition of courgette (zucchini) plants (Cucurbita pepo L.) was investigated.

Relative nitrogen mineralization and nitrification in soils of two contrasting hardwood forests: Effects of site microclimate and initial soil chemistry

This study determined the relative rates of soil nitrogen mineralization and nitrification in neighbouring mixed oak and mixed mesophytic forest stands on sandstone-derived soils in Neotoma Valley, south central Ohio, U.S.A. The soils of the northeast-facing mesophytic stand had higher pH, moisture, and extractable nutrient levels while those of the southwest-facing oak stand were deeper and had a higher C: N ratio. To evaluate the relative importance of initial soil chemical status and microclimate in controlling nitrogen transformation rates, the polyethylene buried-bag method was modified to include reciprocal transplants of bags between sites. Nitrogen mineralization was greater at the mesophytic site most of the year, though the rates were not different between sites during a very dry September. Total annual N mineralization per gram of soil and per m 2 of forest floor were 208 μg N g −1 dry soil and 5604 mg N m −2, respectively. The comparable rates for the mixed oak site were 125 μg N g −1 and 2209 mg N m −2. Approximately 67% of monthly mineralized N was nitrified at the mesophytic site while less than 10% was nitrified at the mixed oak site. Differences in both mineralization and net nitrification rates between sites correlated positively with ammonium pool size and moisture, and negatively with nitrate pool size, while percent nitrification was positively correlated with pH and negatively with C: N ratio. In contrast, seasonal patterns of N transformation within a site were strongly correlated with soil temperature and moisture, and relatively unaffected by soil chemical factors. The rate of N mineralization and relative nitrification in transplanted bags did not differ from those of bags incubated at their native site. Thus, within this watershed, spatial variations in nitrogen dynamics were more closely related to differences in soil chemistry than to microclimate, while seasonal patterns showed just the reverse.

Effects of soil acidification and subsequent leaching on levels of extractable nutrients in a soil

The effects of soil acidification (pH values from 6.5 to 3.8), and subsequent leaching, on levels of extractable nutrients in a soil were studied in a laboratory experiment. Below pH 5.5, acidification resulted in large increases in the amounts of exchangeable Al in the soil. Simultaneously, exchangeable cations were displayed from exchange sites and Ca, Mg, K and Na in soil solution increased markedly. With increasing soil acidification, increasing amounts of cations were leached; the magnitude of leaching loss was in the same order as the cations were present in the soil: Ca2+>Mg2+>K+>Na+.

Influences of frost-heaving on vegetation and nutrient regime of polygon-patterned ground

Actively frost-heaved polygon ground in an alpine area of nutrient-poor shrub heaths, had a large number of basophilous vascular plant species and cryptogams. The soils of the polygons had much higher concentrations of extractable plant nutrients and higher pH values than the surrounding stable ground, probably due to mixing of soils, intense weathering of the raw soil and lack of podzolization under conditions of high frost activity. Plant distribution was correlated to the intensity of frost-heaving; basophyte dominance was consistent with high pH and high extractable nutrient levels on the most actively upheaved polygon centres, whereas heath vegetation became increasingly dominant towards polygon borders with weaker activity, and on polygons with weak recent activity. Empetrum-heath species, usually distributed at sites with thin snow cover during winter, seemed better adapted to weak frost-heaving than species characteristic of communities normally developed in places with medium snow cover.

A Descriptive Model of Soil Test Nutrient Levels Following Fertilization

AbstractFor efficient utilization of fertilizer, a practical means of expressing the residual effect of certain plant nutrients is needed. A descriptive model was developed to show the change in extractable nutrient levels with time assuming a rapid increase after fertilization followed by a slower exponential decrease. The information needed or parameters for the model include (i) the equilibrium soil test level, (ii) the magnitude of the initial sorption reaction, and (iii) a loss constant. These were determined for seven long‐term fertilizer studies with phosphorus (P). There was a large difference in P‐sorption capacity of the soils; all parameters reflected this difference. The initial sorption reaction was linearly related to rate of fertilization in some soils and quadratically in others. The model was applied to conditions in which fertilizer was applied at various time intervals. Good agreement between observed and predicted values was obtained. The main value of this model is to be able to calculate the amount of fertilizer needed to establish and maintain a given soil test level.

NUTRIENT AND HEAVY METAL TRANSPORT CAPABILITIES OF SEDIMENT IN THE SOUTHWESTERN UNITED STATES1

ABSTRACT: Most studies of nutrient loss from small study watersheds ignore a potentially important loss transported by the suspended sediment load. We proposed that the geology and vegetation of a watershed are predictors of the nutrient and heavy metal transporting capacity of its suspended sediment. Analyses of acid‐digestable and extractable nutrients showed differences for sediments derived from ponderosa pine forests in the Southwest on different geologies. These differences were similar for soil, stream bank, and stream channel material for a given site. Suspended sediment collections had nutrient concentrations similar to those of stream channel collections. Different vegetation on a given geology affected primarily the organic matter content, cation exchange capacity, total P, and levels of extractable nutrients in sediment.