Communications in Soil Science and Plant Analysis

Wilson, M. A.; Burt, R.; Lynn, W. C.; Klameth, L. C.

doi: 10.1080/00103629709369800pmid: N/A

Abstract The standard digestion method for total elemental analysis of soil material by the Soil Survey Laboratory (USDA Natural Resources Conservation Service) uses a 2‐mL clay suspension with hydrofluoric acid (HF) in a closed Teflon digestion vessel (method HF‐SUS). The accuracy and efficiency of elemental recovery by method HF‐SUS was compared to: (a) modification of HF‐SUS by use of a dried sample (method HF‐DRI); (b) modification of HF‐SUS by use of a dried sample and HF+aqua regia (method HF+AR); (c) sample digestion by Li metaborate fusion (method FUS); and (d) microwave digestion of samples with HF+aqua regia in Teflon bombs (method MICRO). Three replications of three standard reference materials (SRMs), fine‐earth (<2 mm) from 12 soils, and the clay (<2 urn) from 10 of those soils were analyzed. Method HF+AR shows the most consistent statistical agreement with the certified SRM values. Analysis of variance (ANOVA) indicates significant effects (α=0.05) for method of digestion, nonsignificant effects for method times SRM and method times clay, but significant effects for method times fine‐earth. Composition and/or variability of material are significant factors in the method of digestion. Method HF+AR yields significantly higher experimental means of A12O3, Fe2O3, and K2O contents and oxide recovery (summation of experimental means for oxides of all reported elements) than all other methods.

Saviozzi, A.; Riffaldi, R.; Levi‐Minzi, R.; Panichi, A.

doi: 10.1080/00103629709369801pmid: N/A

Abstract Changes in chemical and mineralogical characteristics associated with different particle size fractions in soil after 40 years of continuous production of corn by the conventional tillage method (CC) as compared with those of an adjacent native grassland site (NG) are investigated. Results indicate that corn cropping in a soil previously supporting native vegetation produces a decline in total and humified organic matter, phenolic compounds, enzymatic activities, cation exchange capacity (CEC), and hydrosoluble ions, both in the whole soil and in its particle‐size separates. The’ largest losses in organic carbon (C) and nitrogen (N) contents of the cultivated soil were observed in the sandy fractions, the lowest in the silt+clay separates. The humification index (HI) indicates a higher degree of humification of the organic matter in NG than in CC samples. For both NG and CC sites the finest fraction (silt+clay) resulted to be enriched in organic C, total N, humus, phenolic compounds, enzyme activity, CEC, and hydrosoluble ions with the only exception of mineral N forms and sulphates (SO4). Slight differences were observed in the mineralogical composition of NG and CC soils. The sandy fractions of NG showed greater amounts of phyllosilicates while a lower content was found in the silt+clay fraction of CC as a consequence of a crumbling of parent rock into small pieces induced by repeated tillage practices.

Rashid, A.; Rafique, E.; Bughio, N.

doi: 10.1080/00103629709369802pmid: N/A

Abstract Boron (B) deficiency in crops is a major micronutrient disorder particularly in alkaline‐calcareous soils. A nutrient indexing of rainfed sorghum [Sorghum bicolor (L.) Merr; cv. Potohar 4–8] in the Potohar plateau of Pakistan revealed B deficiency in 50% of the 140 sampled fields in Jehlum district and 115 fields in Chakwal district. Hot water extractable (HWE) B in the associated soils, however, indicated more widespread B deficiency. The 255 sampled fields represented 21 soil series: 100 belonging to Alfisols, 63 to Entisols, 50 to Inceptisols, and 42 to Aridisols. Boron fertility varied in various soil types; the minimum HWE B (0.25 mg/kg) was noted in Calci Ustochrepts and the maximum (0.69 mg/kg) in Fleventic Ustochrepts. Boron fertilization of an alkaline calcareous Typic Ustorthents (HWE B, 0.11 mg/kg) increased grain yield up to 32% in improved sorghum (cv. PARC‐SS‐1) and 29% in local sorghum (cv. Potohar 4–8) over the respective control yields. Fertilizer requirements for near‐maximum (95%) grain yield was 1.2 mg B/kg for the improved and 0.6 mg B/kg for local cultivar; higher fertilizer requirement of improved sorghum may be attributed to its greater biomass production. Critical plant tissue B concentration in improved sorghum was 17 mg/kg in whole shoots and 25 mg/kg in most recently matured leaves. Contrary to its lesser fertilizer requirement, internal B requirement of local sorghum was greater, i.e., 18 mg/kg in whole shoots and 31 mg/kg in leaves. The three soil tests for B, hot water, hydrochloric acid (HC1), and mannitol were almost equally effective in evaluating soil B fertility. Soil test critical B levels (mg/ kg) for improved sorghum were: hot water, 0.48; HC1, 0.43; and mannitol, 0.37. Contrary to its internal B requirements, soil test critical B levels (mg/ kg) were slightly lower for local sorghum, i.e., hot water, 0.45; HC1, 0.40; and mannitol, 0.36. Thus, local sorghum appeared more efficient in utilizing soil B. As soil test critical levels as well as fertilizer requirement were greater for improved sorghum, a much widespread B deficiency is expected in this cultivar if grown on alkaline calcareous soils of the Potohar plateau.

Rashid, A.; Rafique, E.; Bughio, N.; Yasin, M.

doi: 10.1080/00103629709369803pmid: N/A

Abstract Zinc (Zn) deficiency in crops is a major micronutrient disorder particularly in alkaline‐calcareous soils like those of the rainfed Potohar plateau in Pakistan. A nutrient indexing of sorghum (cv. Potohar 4–8) by sampling <30 cm tall whole shoots and associated soils from 255 random field locations revealed that the crop was deficient in Zn in 54% fields in Jehlum district and 64% in Chakwal. In a greenhouse experiment using a Zn‐deficient calcareous Typic Ustorthents, maximum increase in grain yield with Zn fertilizer was 177% over control in improved sorghum variety (cv. PARC‐SS‐1) and only 10% in local sorghum (cv. Potohar 4–8). Although biomass production of cv. PARC‐SS‐1 was much greater compared with cv. Potohar 4–8, fertilizer Zn requirement for the two cultivars was not much different, 8.3 mg Zn/kg soil for improved sorghum variety and 7.3 mg Zn/kg for local sorghum variety. Contrary to its higher sensitivity to Zn deficiency, the improved sorghum variety was more efficient in utilizing fertilizer Zn. Despite low Zn availability in the Potohar fields, local sorghum is not expected to respond to fertilizer Zn. However, adequate Zn fertility must be assured for cultivating improved sorghum in these soils. Zinc content in mature grains of sorghum proved a good index of soil Zn fertility status. Internal Zn requirement in foliar plant parts of cv. PARC‐SS‐1 (whole shoots, 33 mg/kg; leaves, 22 mg/kg) was greater than in cv. Potohar 4–8 (whole shoots, 27 mg/kg; leaves, 20 mg/kg). In contrast, critical Zn content in grains of the improved sorghum variety (10 mg/kg) was lower than of local variety (14 mg/kg). Three soil tests were equally effective in determining soil Zn fertility. Critical soil Zn levels for cv. PARC‐SS‐1 were: DTPA, 3.4 mg/kg; AB‐DTPA, 3.7 mg/kg; and Mehlich 3, 8.0 mg/dm3. Similar to internal Zn requirement in foliar plant parts, soil test critical Zn levels were lower for cv. Potohar 4–8, i.e., DTPA, 3.1 mg/kg; AB‐DTPA, 3.5 mg/kg; and Mehlich 3, 7.2 mg/dm3. Because of their better efficiency, ‘universal’ soil tests appear superior to the DTPA test for routine Zn analysis.

Sims, J. L.; Wells, K. L.; Ditsch, D. C.; Clark, J. D.

doi: 10.1080/00103629709369804pmid: N/A

Abstract Field experiments were conducted during 4 years at two locations in Kentucky to study the response of burley tobacco to phosphorus (P) and potassium (K) fertilizer rate and placement, and to in‐row subsoiling. In one experiment on Pope soil (mesic Fluventic Dystrochrepts), dry matter and P and K uptake 40 days after transplanting, and cured leaf yield and value/ha were increased as application of a 5–13–36 (%N‐P2O5‐K2O) grade fertilizer increased from 310 to 930 kg/ha. Generally, fertilizer placed in 40‐cm wide bands directly under and parallel to the row was more effective than broadcasting and in‐row subsoiling was more effective than not subsoiling. Significant 2‐way and 3‐way interactions suggested that plant responses to band applications over broadcasting were greater in the presence than absence of subsoiling. In another experiment conducted on two silt loam soils, Pope and Maury (typic Paleudalfs), fertilizer applied in a 40‐cm band with in‐row subsoiling was more effective than broadcasting without subsoiling or placement in 10‐cm wide bands applied 0.6‐m apart and perpendicular to the row without subsoiling. Growth and yields increased up to the 620 kg/ha rate and 40 days after transplanting, soil pH decreased and soil electrical conductivity and plant manganese (Mn) increased with increased rate of fertilizer.

Fernandes, M. L.; Coutinho, J.

doi: 10.1080/00103629709369805pmid: N/A

Abstract Ion exchange resin methods were applied to 78 different soils to assess their phosphorus (P) status for predicting their response to P fertilization. The techniques used were anion exchange resin membranes eluted with hydrochloric acid (HCl) (AEM) and cation‐anion exchange resin membranes eluted with HCl (CAEM‐HC1), sodium chloride (NaCl) (CAEM‐NaCl) or water with directly color development (CAEM‐H2O). Greenhouse studies were conducted with the same soils in order to validate laboratory data. Ryegrass was grown with two levels of P: nil and 150 mg P kg‐1 of soil. Results indicate that soil P levels are significantly correlated (p<0.001) if extracted with AEM or CAEM, both eluted with HCl, although the CAEM technique had extracted larger amounts of P. Concerning the type of elution, results did not show significant differences (p<0.05) between CAEM‐HC1 and CAEM‐NaCl, but both were significantly correlated (p<0.001) with the results obtained with CAEM‐H2O. All the techniques used to measure extractable P correlated significantly with relative yield and P uptake by ryegrass, showing their ability to predict soil P availability. Nevertheless, CAEM extraction had higher values of r2. Among the three techniques for elution, the levels of correlation with the biological parameters were equivalent. From these results, it was concluded that: (i) exchange resins, specially CAEM, is an accurate method to assess the P fertility status of soils, and (ii) the traditional step of elution can be avoided, allowing the process to be less time consuming, thus more suitable for routine use.

Starrett, Steven K.; Starrett, Shelli K.; Adams, G. L.

doi: 10.1080/00103629709369806pmid: N/A

Abstract The objective of this study was to develop an Artificial Neural Network (ANN) model that accurately predicts the percentage of applied nitrogen (N) that leaches through the upper 50 cm of soil under a variety of conditions. The statistical regression models were used for comparison with the ANN model. The Sum of the Squared Error (SSE) between the anticipated values (from research data) and the predicted values (produced by the model) was calculated to be 0.3 for the ANN model and 0.1 for the third order regression. In this particular project, the first and second order regression equations are not useful; however, the third order equation could be used by turf managers along side the ANN model to accurately predict leachate under given field conditions. These models enable the turfgrass manager to determine the effects of management practices on N leaching.

Vlyssides, A. G.; Bouranis, D. L.; Loizidou, M.

doi: 10.1080/00103629709369807pmid: N/A

Abstract A new mathematical approach is presented for evaluating the inherent capacity of an organic soil conditioner to supply nutrients to plants in suitable proportions or to bind to prevent toxicities. This approach is based on the concept that the rate of elution of any nutrient follows a first‐order mathematical model. By using experimental data collected from an elution apparatus, the method enables the evaluation of two parameters, the specific nutrient elution rate and the maximum extractable amount of the nutrient. The elution rate coefficient can be used for the evaluation of the slow release ability that is imparted by a soil conditioner for an ion or a substrate. The maximum extractable amount can then be used for the evaluation of the soil conditioner's ability to hold the compounds, thereby inactivating them by immobilization. An example of this mathematical approach is given.

Zurayk, Rami; Nimah, Musa; Geha, Yolla; Rizk, Charbel

doi: 10.1080/00103629709369808pmid: N/A

Abstract Constructed wetlands may be described as soil/plant systems for wastewater treatment in which pollutant removal is based on general principles of nutrient transformation in soils. Currently perceived as “black boxes”; by engineers, the design and operation of these systems may be greatly improved based on the knowledge gained from several decades of studying nutrient cycling in soil‐plant systems. This paper reports on an attempt to operate this linkage. Three pilot scale systems planted with reed, cattail, and water hyacinth were used to study the role of the soil matrix in phosphorus (P) removal over a period of five months. Phosphorus removal was superior in the soil‐based systems with a mean P reduction from the influent concentration (24 mg‐mL‐1) of 80% compared with 54% in the soilless bed. Recycling the effluent into the system in order to increase the detention time did not contribute to improving removal, except in the soilless bed. This indicates that P removal in the soil‐based systems is rapid, and that an equilibrium value may be reached beyond which no further removal is possible. The effect of a lime amendment on the improvement of P removal was studied in batch tests in a decarbonated sand amended with 1.4%, 12.2%, 21%, 38%, and 49% calcium carbonate (CaCO3). Phosphorus removal from solution can be significantly improved by the addition of small amounts of lime (2–4%). Fixation is also faster and sustainable in lime‐amended sands. These results suggest that P removal from wastewater can be greatly enhanced by the addition of small amounts of lime to the soil substrate.

Antep, S.

doi: 10.1080/00103629709369809pmid: N/A

Abstract The large increases in nitrogen (N) fertilizer usage in recent years have led to a recognition of the need for reliable and quick methods of measuring the N‐supplying capacities of soil. Despite this need, there is no well accepted method for testing soils for N availability that has been generally considered to be satisfactory. This study was conducted to determine the N status of the soils of the Bafra Plain and to evaluate some of the more promising methods of determining the index of soil N availability by using a 15N technique as a standard. Twelve representative soil samples were collected having a broad range of chemical and physical characteristics. In determining the available N contents of these soils, one aerobic incubation method and 12 different chemical methods were compared. In order to evaluate the availability of indigenous soil N to plants and also to investigate the N status of these soils, a greenhouse experiment was conducted with corn as the test plant. Nitrogen was applied as urea at the rate of 0, 50, 100, and 200 ppm with 15N enriched (2% a.e) urea used at the 50 ppm rate. After eight weeks of growth, plants were harvested. The increased amounts of N were not affected linearly by the dry matter, N content, and N uptake by the corn plants for most of the soils. The most suitable N rate was found to be 50 ppm N under the experimental conditions. In order to select the most suitable chemical methods, the AN‐value (soil N availability to plant as the applied fertilizer N) was taken as the standard method. Highly significant correlation coefficients were obtained between the AN‐value and each of the following methods: alkaline hydrolysis (r=0.900 and r=0.938, P<0.001), alkaline permanganate (r= 0.873, r=0.864 and r=0.826, P<0.001), and total N (r=0.850, P<0.001), respectively. These methods appeared worthy of consideration as a routine test for assessing the N availability for these soils.