Monitoring the combined action of controlled‐release fertilizers and a soil conditioner in soil

Abstract

The combined action of a soil conditioner and a controlled‐release fertilizer was followed by conducting soil column leaching and tomato growth experiments. The change in soil water‐holding capacitiy and the release of potassium sulfate (K₂SO₄) from conventional and controlled‐release forms was evaluated using leaching experiments in soil columns. Tomato growth was followed by the comparison of biomass yields on a dry matter basis with experiments where different combinations of controlled‐release or conventional fertilizer rates and soil conditioner applications. It was demonstrated that the combined usage of controlled‐release fertilizers and soil conditioners increased tomato yield and enhanced the nutritional status of the tomato plants in comparison to conventional fertilizer materials.     

Potassium release from selected slow‐release fertilizers

Abstract

Potassium (K) release rate from Osmocote 14–6.3–11.6 (N‐P‐k), MagAmp 7–18–5, Choice 10–4.3–8.3, Scotts 21–3–5.8 and Unimix 10–8.7–4.2 was determined. During the 63‐day experiment Osmocote and Scotts had relatively linear release rates while the release rate from the other fertilizers was initially rapid and decreased over time.     

Forecasting by laboratory tests of nitrogen leached and absorbed in soil‐plant system with urea‐based controlled‐release fertilizers coated with lignin

Abstract

In order to predict release of nitrogen (N) from controlled‐release fertilizers (CRF) from laboratory experiments, new types of lignin‐coated fertilizers were studied. Laboratory methods were 1) release of urea into water and 2) an extraction procedure using an electroultrafiltration technique (EUF). The results of these two methods were compared to the amount of N released in a vegetation experiment in the greenhouse. The results showed a good relationship between the two laboratory methods. The correlation coefficient between the rate constant K determined in the water extract and each of the N‐fractions was highly significant. The total amount of N released in the vegetation experiment was correlated to parameters of the laboratory methods. The N uptake by the plant was significantly correlated with the first order constant and with the fertilizer's EUF‐NII index. The N leached was also correlated with the EUF‐NI and EUF‐N (I+II) indices.     

Response of four woody ornamental species to superphosphate and controlled‐release fertilizers

Abstract

Shoot dry weights of Ilex vomitoria Ait. ‘Schellings Dwarf’, Pittosporum tobira Thunb., and Juniperus chinensis L. ‘Blue Vase’ fertilized with Sref 20N‐2P‐8K and Step (micronutrient formulation) or Osmocote 18N‐3P‐10K and Micromax (micronutrient formulation) were not different when grown in a 1 sedge peat: 1 cypress sawdust: 1 cypress shavings (v/v/v) medium with or without superphosphate. Photinia X fraseri Dress shoot and root dry weights decreased if supersphosphate was added to the growing medium and fertilized with Sref and Step, but were not different when fertilized with Osmocote and Micromax. Shoot tissue P levels of P. X fraseri and P. tobira increased with the addition of superphosphate regardless if Osmocote and Micromax or Sref and Step were used, but there was no corresponding increase in shoot dry weight. Water soluble P levels of the superphosphate amended medium with Sref and Step decreased about 70 ppm during the 6‐month experimental period.     

Leaching of nitrogen forms from controlled‐release nitrogen fertilizers

Abstract

Application of soluble forms of nitrogen (N) fertilizers to sandy soils may cause leaching of nitrate N (NO₃‐N) resulting in contamination of groundwater. The leaching loss of N may be reduced to a certain extent by the use of controlled‐release N formulations. A leaching column study was conducted to evaluate the leaching of urea, ammonium N (NH₄‐N), and NO₃‐N forms from selected urea‐based controlled‐release formulations (Meister, Osmocote, and Poly‐S) and uncoated urea under eight cycles of intermittent leaching and dry conditions. Following leaching of 1,760 mL of water (equivalent to 40 cm rainfall) through the soil columns, the recovery of total N (sum of all forms) in the leachate accounted for 28, 12, 6, or 5% of the total N applied as urea, Poly‐S, Meister, and Osmocote, respectively. Loss of urea‐N from all fertilizer sources was pronounced during the initial leaching events (with the exception of Meister). Cumulative leaching of urea‐N was 10% for uncoated urea while <1.7% for the controlled‐release formulations. Cumulative leaching of NH₄‐N was 6.2% for uncoated urea while <0.5% for the controlled‐release formulations. Cumulative leaching loss of NO₃‐N was 3.78% for Osmocote, 4.6% for Meister, 10.4% for urea, and 10.5% for Poly‐S. This study demonstrates a significant reduction in leaching of N forms from controlled‐release formulations as compared to that from the soluble form.     

Manganese‐iron interactions in the plant‐soil system

Dicotyledonous plants had significantly higher Mn and Fe intake rates on a near neutral soil, had a significantly higher Mn intake rate on a slightly calcareous soil, but had lower Mn and Fe intake rates on a calcareous soil, than monocotyledonous plants. This dependency on soil reaction suggests that dicots utilize primarily a chemical reduction mechanism, whereas monocots utilize some less pH‐dependent mechanism (possibly Mn(III)‐, Fe(III)‐organic complexation) to mobilize soil Mn and Fe. Soluble soil Mn and Fe fractions in the rhizosphere were consistently positively correlated with each other, as were Mn and Fe intake rates. These results suggest that for soil‐grown plants, Mn and Fe uptake was positively interrelated because both Mn and Fe were mobilized by similar root processes.     

Response of alfalfa to a phillipsite‐based slow‐release fertilizer

Abstract

A greenhouse experiment was conducted with alfalfa (Medicago sativa L. cv. Aragon wide leaf) to test the performance of a zeolite (phillipsite) phosphorus‐potassium (P‐K) fertilizer versus soluble potassium dihydrogen phosphate (KH₂PO₄) applied to a coarse‐textured substratum consisting of a mixture 1: 4 (in volume) soihbasaltic ash. Plants were sown at four fertilization rates and five harvests were collected after nine months. The nutrient content in plant tissue was higher in the plants treated with zeolitic fertilizer, although the response was primarily due to P. No differences due to the fertilizer source were observed for dry matter yield. When considering nutrient uptake, differences between the two fertilizers were enhanced, although the results for P are more pronounced. The soil nutrient content found after the experiment shows that available P was significantly higher in those pots that received the zeolite fertilizer, but no differences were found for K.     

Assessment of soil and plant analysis laboratories in the West Asia‐North Africa Region

Abstract

Although limited amount of water is the primary constraint to agricultural productivity in the rainfed area of West Asia and North Africa (WANA), yields are also low because of the poor mineral nutrient status of soils. Yields can, therefore, be considerably increased by judicious fertilizer use. Laboratories for soil and plant analysis are essential for identifying nutrient constraints and providing a basis for efficient fertilizer use, through correlation studies to establish suitable soil testing extractants and calibration studies with crop responses. The Soils Laboratory at the International Center for Agricultural Research in the Dry Areas (ICARDA) has initiated a quality control program among the national agricultural research systems (NARS) in the countries of the WANA region. The efforts include linkages with the Wageningen International Soil Analytical Exchange Program, in‐country training courses, and a laboratory analysis manual. Continued improvement in laboratory performance is dependent upon knowledge of the capabilities of such laboratories and identification of their constraints. This presentation reports a fact‐finding survey of laboratories from 16 countries of the WANA region—mainly public, from universities and ministries of agriculture, and some private or commercial ones—based on a questionnaire about analyses, facilities, methodologies, quality assurance, personnel training, and management. Future efforts to improve the quantity and quality output from of these laboratories will address such deficiencies.     

Pattern of iron distribution in the soil‐plant system and its possible relation to iron‐chlorosis

Abstract

The frequent concentration‐ranges of various nutrient elements in soils and in plants are compared. Iron is different from almost all other nutrient elements in the fact that its optimal concentration range in plants is much lower than its frequent concentration range in soils. It is suggested that this observation is related to a chemical‐physiological mechanism of control on the uptake of iron by plants which in turn may explain the situations in which iron deficiency conditions in plants arise.     

Effect of High‐Molybdenum Compost on Soils and the Growth of Lettuce and Barley

A pot experiment evaluated the growth of lettuce (Lactuca sativa L.) and barley (Hordeum vulgar) and accumulation of molybdenum (Mo) in plants and soils following amendments of Mo compost (1.0 g kg^?1) to a Truro sandy loam. The treatments consisted of 0 (control), 12.5, 25, and 50% Mo compost by volume. The Mo compost did not affect dry‐matter yield (DMY) up to 25% compost, but DMY decreased at the 50% compost treatment. The 50% compost treatments increased the soil pH an average of 0.5 units and increased the nitric acid (HNO₃)–extractable Mo to 150 mg kg^?1 and diethylenetriaminepentaacetic acid (DTPA)–extractable Mo to 100 mg kg^?1 in the growth medium; the same treatment increased tissue Mo concentration to 569 and 478 mg kg^?1 in the lettuce and barley, respectively. Plants grown in the 25% compost produced about 55 mg kg^?1 of total Mo in the growth medium; this resulted in tissue Mo concentration of 348 mg kg^?1 in lettuce and 274 mg kg^?1 in barley without any phytotoxicity. Our results suggested that 55 mg Mo kg^?1 soil would be an appropriate limit for Mo loading of soil developed from compost additions, a value which is presently greater than the Canadian Council for Ministers of the Environment (CCME) Guidelines for the use of type B compost in Canada.     

Shoot growth,plant tissue elemental composition,and soil salinity following irrigation of alfalfa and tall fescue with high‐sulfate waters 1

Groundwater contaminated with sulfate (SO₄ ^2‐) at concentrations higher than allowable for drinking water might still be usable for irrigation. Objectives were to determine the growth response and mineral uptake of two forage crops irrigated with waters containing SO₄ ^2‐ at concentrations ranging from 175 to 1743 mg/L, and with electrical conductivities (EC) ranging from 1.2 to 3.6 dS/m. Plants were grown for 12 weeks in 8‐L pots containing a calcareous sandy loam and were harvested at 4, 8, or 12 weeks for plant growth measurements and tissue analysis. Digested leaves, stems, and reproductive tissues were analyzed by inductively coupled plasma (ICP) spectroscopy at each harvest, as were saturated soil paste extracts. Shoot growth of tall fescue (Festuca arundinacea Schreb.) was not affected by irrigation water treatment, whereas shoot growth of alfalfa (Medicago sativa L.) was increased by a moderate level of soil solution SO₄ ^2‐ Sulfur (S), boron (B), magnesium (Mg), sodium (Na), and zinc (Zn) concentrations in shoot tissues of both species showed a tendency to increase with increasing SO₄ ^2‐ content of irrigation water. Shoot tissue concentration of molybdenum (Mo) increased with maturation in both species, while the concentrations of B, potassium (K), manganese (Mn), Na, and Zn decreased. Soil saturated paste extract concentrations of Mg and Na increased with irrigation water Mg and Na concentrations, while Ca and S concentrations in the soil solution became saturated at the higher irrigation water concentrations of these elements.     

Urea release from Osmocote® fertilizers in water and simulated wetland rice soil

Abstract

Average urea release (UR) from two Osmocote fertilizers (40–0–0 and 41–0–0) in water at 38°C and in a simulated wetland system using Crowley soil under greenhouse conditions has been studied. UR from the Osmocote granules in water seemed to be a diffusion process controlled by urea concentration gradients. It was faster when the swelling of granules was restricted than when swelling of granules was not restricted. The UR‐time curves for both Osmocote fertilizers placed at different depths (0–1, 5–10, and 10–15 cm) in simulated wetland soil were different from those placed in water. UR in the soil was rather slow; therefore, these fertilizers may not be suitable for short‐ to medium‐duration wetland rice varieties.     

Amelioration of saline‐sodic soils with organic matter and their use for wheat growth

Abstract

Few reports highlight the effect of organic matter in improving the properties of saline soils. A laboratory study was conducted to determine the effect of adding farm yard manure (manure), Egyptian clover hay (clover hay), and wheat straw, at 1 and 3% of soil weight on water stability of soil aggregates (WSA), water‐holding capacity (WHC), pH, and electrical conductivity of soil extract (ECe) of a normal, saline, and saline sodic soil. After 90 and 180 days, WSA and WHC increased, while pH and ECe decreased. Soil properties improved most by adding 3% manure to all the soils. Wheat grown in these soils indicated significant differences for various growth and yield variables, especially the root growth, number and area of green leaves, and grain yield. Organic matter added to these soils increased WSA and WHC and decreased pH and Ece. The WHC had no correlation with pH, but was negatively correlated with Ece. Increased WSA caused the leaching of excess ions and reduced their toxicity, while enhanced WHC increased the availability of water to the roots and promoted growth. It is concluded that manure ameliorated salt affected soils and promoted wheat growth better than clover hay and wheat straw.     

Some characteristics of a new organic soil conditioner from the co‐composting of olive oil processing wastewater and solid residue

Abstract

The effectiveness of a new organic soil conditioner from the co‐composting of olive oil processing wastewater and solid residue was examined through the evaluation of some of its physical and chemical characteristics. The concentration of 25% w/w of this material into the conditioner‐soil mixtures appears to be the maximum level for the cultivation of tomato plants. The plants grown on this conditioner‐soil mixture were 1.52±8.5% times larger than those grown on a sandy loam soil. The pure conditioner cannot be used as a substrate for the growth of tomato plants. The water‐holding capacity of the conditioner was almost two times higher than that of the pure soil and remained almost stable for temperatures between 8–40°C. The apparent density of the conditioner was 0.5 times smaller than that of the pure soil. With increased application rate of the conditioner to the soil, there was a decrease in the pH, an increase in the specific conductivity, and an increase in the ammonium‐nitrogen (NH₄‐N) and phosphorus (P) concentration of the mixture.     

Residual effects of sewage‐sludge application on plant and soil‐profile chemical composition

Abstract

Long‐term effects on plant and soil‐profile chemical composition imposed by a residential sewage sludge were studied on an Oxisol from Hawaii. Sludge was applied at 0, 45, 90, and 180 Mg/ha in 1983. An NPK‐fertilized treatment was included for comparison. Sudangrass (Sorghum bicolorL. Moench) was grown as a test crop in the 1983–84 and 1986–87 seasons. Soil samples for chemical analysis were taken in 1987 at three depths: 0–23 cm, 23–46 cm, and 46–69 cm.

Beneficial effects of sludge, measured 3 years after application (beginning of the 1986's planting), were evident by large yield increases on sludge‐amended soils relative to the unamended and the NPK‐fertilized soils. The first cutting produced approximately 5 Mg/ha of dry matter from the sludge treatments, regardless of rate, as compared with 3 and 1.5 Mg/ha from the NPK and the 0 treatments. Regrowths showed similar effect, though less dramatic; average yields were 2.6 Mg/ha with sludge and 1.6 Mg/ha without.

Heavy‐metal concentrations in plants were generally unaffected by sludge applications; probably because (i) heavy‐metal contents of the sludge were low, and (ii) soil pH was increased by sludge.

Remarkable increases in pH, exchangeable Ca and extractable P, and resultant decreases in exchangeable Al, in all three soil layers of sludge‐amended soils suggest that surface application of a low heavy‐metal sludge could serve to correct subsoil acidity and enhance subsoil P availability.     

Longevities and nitrogen,phosphorus, and potassium release patterns of polymer‐coated controlled‐release fertilizers at 30°C and 40°C

Abstract

The weekly nitrogen (N), phosphorus (P), and potassium (K) release from 17 polymer‐coated controlled‐release fertilizer (CRF) formulations of Nutricote, Apex Gold, Osmocote, and a 9‐month Macrocote were measured at 30.6±0.8°C and 40.0±1.5°C. Five grams of each CRF were placed at a depth of 50 mm in 280x50 mm acid washed then rinsed silica sand columns which were leached with deionized water three times each week until nutrient recovery ceased. The volume of leachate was recorded each week and subsampled for ammonium‐N, nitrate‐N, phosphate‐P, and K analyses. Each CRF treatment was replicated three times at each temperature. Nutrient release profiles were determined. Longevities, measured as weeks to 90% nutrient recovery, were considerably shorter than the nominated release periods for all formulations. Within each CRF product group, the longevity of 9 and 12 month formulations were similar with Apex Gold 12–14 month high nitrate having the longest (38 weeks for N at 30°C) and Osmocote 8–9 month the shortest (23 weeks for N at 30°C). There were consistent trends in the nutrient release periods across all CRFs with P>K>N and with differences of around 10% in duration between nutrients. The P:N release ratio exceeded 0.10 for most CRFs during the early release period indicating an adequate P supply for most plant species. The mean reduction in longevity for Nutricote, Apex Gold, and Osmocote formulations for an increase in incubation temperature from 30°C to 40°C was 19–21 % for N, 13–14% for P, and 14–15% for K. All CRFs released nutrients unevenly with the highest rate occurring during the early part of the release period. This pattern was accentuated at 40°C and by the shorter term release formulations. The nutrient release rates of all CRFs declined steadily after their maxima.     

Localized root growth in soil induced by controlled‐release urea granule and barley nitrogen uptake

Controlled‐release urea is a fertilizer which meters out urea over a long period of time. It can provide a favorable nitrogen (N) concentration for root growth, especially at the early stage of plant development. The objective of this study was to determine the interactions of urea or controlled‐release urea granules with barley roots and the resultant N uptake by plants. Two experiments (Experiment I and Experiment II) with treatments of Nil, non‐coated urea, Coated I and Coated II (Coated I and Coated II are controlled‐release urea products) were conducted in a greenhouse at 23±5°C. In both experiments, one barley (Hordeum vulgare L. cv. Duke) seed and one granule of urea or controlled‐release urea were placed in a pot (5.2‐cm height and 8‐cm diameter) containing soil low in mineral N. In Experiment I, shoot and soil samples were taken at 14, 28, and 46 days after seeding. Roots and fertilizer interaction were visually examined and photographed. In Experiment II, root samples both around the fertilizer granule and away from the granule were taken only at 28 days after seeding. In both experiments, dry matter mass and total N content of shoot and root, and mineral N in soil were determined. In Experiment I, at the 28‐day sampling roots proliferated around the controlled‐release urea granule but not around the urea granule. Shoot N uptake since the 28 days was higher with controlled‐release urea than with urea because of the root proliferation. In Experiment II, root dry mass and N content around the granule was higher with controlled‐release urea than with urea. In the controlled‐release urea treatments, root mass and N content away from the granule were also increased in comparison to the Nil. This shows a stimulus relationship between the two portions of the roots in the same plant, i.e., the roots being accessed to the N source increased growth of the other roots with no access to the source. Because only a small portion of roots was involved in N uptake in the controlled‐release urea treatments, the intensity of N uptake per unit of root mass was much higher with controlled‐release urea as compared to urea. In conclusion, root growth was enhanced around controlled‐release urea granule, and that portion of roots around the fertilizer granule played a major role in absorbing N. In addition, a stimulus relationship existed between roots grown around the granule and those grown away from the granule.     

The effect of gamma‐radiation on the release of carbon dioxide from fresh soil

Abstract

The release of CO₂ from fresh soil at medium moisture was examined for 14 days after the application of gamma‐radiation over the range 0.025 ‐ 10 Mrad. All doses stimulated the release of CO₂ compared with non‐irradiated soil, but there was no extra yield of gas between 4 and 10 Mrad. Rapid evolution occurred during irradiation and over the next 24 hours, but towards the end of incubation both irradiated and untreated soil produced CO₂ at similar rates.

Studies to elucidate the origin of CO₂ indicated that the contribution from enzymes was predominant up to 2 Mrad, but at 10 Mrad, 45% of the gas could be formed by radiolytic decarboxylation of soil organic matter. Consequently, heavy irradiation of soil cannot stop production of CO₂, and if high concentrations do interfere with the application of radiation to specific soil research investigations, the gas should be displaced or allowed to diffuse from the sample.     

Trace element analyses of fertilizers and soil amendments by axial‐view inductively‐coupled plasma atomic emission spectrophotometry

Abstract

The application of fertilizers and other amendments, including urban and industrial wastes, to agricultural lands is of some concern due to the possibility of soil pollution by heavy metals and, ultimately, deterioration of the environment. Easy, rapid, and safe analytical procedures are therefore required to assess the potential hazard of applying these materials to soils. The objective of this study was to evaluate the potential of axial‐view inductively‐coupled plasma atomic emission (ICP‐AES) for the determination of 17 elements of environmental significance in HNO₃ and HF digests of selected fertilizers and soil amendments. Reliable results were obtained for silver (Ag), barium (Ba), beryllium (Be), cadmium (Cd), and nickel (Ni). The arsenic (As), manganese (Mn) and vanadium (V) analyses were virtually problem free in samples containing low to moderate amounts of chromium (Cr), Ni, and titanium (Ti). Bismuth (Bi), selenium (Se), and thallium (Tl) could not be determined due to spectral interferences and cobalt (Co), Cr, copper (Cu), lead (Pb), antimony (Sb), and zinc (Zn) results were of intermediate quality. Correction of spectral interferences using the multi‐component spectral fitting (MSF) technique was only partially useful for Co and Pb and not necessary or beneficial for other analytes. Axial‐view ICP‐AES is a suitable tool for the routine analyses of trace elements in fertilizers and soil amendments, and its scope could be extended to more analytes provided that more detailed interference studies are carried out. The use of the interelement correction technique (IEC), which was not tested in this study, might be helpful in correcting spectral interferences. The analyte detection limits ranged from <0.7 to 17 μg L^‐1.     

Reducing nitrogen leaching‐losses from containerized plants: The effectiveness of controlled‐release fertilizers

Abstract

To evaluate the effectiveness of controlled‐release fertilizer (CRF) for reducing nitrogen (N) leaching‐losses from containerized greenhouse crops, three experiments were conducted where CRFs were applied in different ways and compared to water‐soluble fertilizer (WSF). In each experiment, ‘First Lady’ marigold (Tagetes erecta L.) plants in 0.5‐liter pots of a soilless growth medium were fertilized with the same amount of ? from 20N‐4.3P‐16.6K WSF, Osmocote 14N‐6.2P‐11.6K CRF, or Nutricote 14N‐6.2P‐11.6K CRF fertilizers. The volume of irrigation water applied to all treatments was the same in each experiment. Nitrogen content, as NH₄‐N and NO₃‐N in container leachates, and plant growth were measured and used to compare WSF with CRFs incorporated in the growth medium, or as applied to the surface, in either one large application or two small doses. A single large application of CRF at planting resulted in as much or more ? leaching than the regular application of WSF. Effectiveness of CRFs in limiting ? leaching was greatly increased by making two smaller applications, the first at planting and the second 15 to 35 days later. More ? was recovered in the leachate when CRFs were incorporated in the growth medium compared to surface application. Regardless of fertilizer type, application method, timing of application, or for each individual experiment, NO₃‐N was the predominant ? form found in the leachate and more than one‐half of the total amount of ? leached during each experiment was recovered within 30 days of planting.