The influence of brine contamination and phospho‐gypsum amendments on soil chemical properties and plant response

Abstract

Phosphogypsum (PG), the by‐product of wet acid production of phosphoric acid from rock phosphate, was found to be effective as a soil conditioner for sodic, solonets, and solonetzic soils. Unlike mine gypsum, PG contains impurities whose release into soil and ground water need to be monitored. PG was incorporated with soils contaminated with oilfield brine to determinate the influence of PG amendments and brine contamination on soil chemical properties and plant response in a growth chamber. Application rates of PG were 0, 25, 50, 100, 200, and 400 Mg ha^‐1 and the testing crop was Barley (Hardeum vulgare L.). Phosphogypsum provides a means of remediating brine spills and can result in benefits expressed as increased plant growth. Soil salinity of brine contaminated soils was ameliorated as evidenced by reduced the electrical conductivity, SAR and exchangeable Na levels in 0–15 cm depth of the columns. There is no evidence that application of PG increased the level of trace elements in plants. Contamination of soil with brine spill is the major factor dominating plant growth and soil‐plant element content. From plant growth point of view, two elements could be excessive, namely Boron (B), and Cadmium (Cd). The high level of B in the plant arose from brine spill and the cause for the excessive Cd level in barley grain is unknown and currently under investigation. The distribution of trace elements in soil profiles demonstrated that there was little, if any, potential for movement of trace elements into greater depths.     

Effect of vegetation changes on soil erosion on the loess plateau

Vegetation is one of the key factors affecting soil erosion on the Loess Plateau. The effects of vegetation destruction and vegetation restoration on soil erosion were quantified using data from long-term field runoff plots established on the eastern slope of the Ziwuling secondary forest region, China and a field survey. The results showed that before the secondary vegetation restoration period （before about 1866-1872）, soil erosion in the Ziwuling region of the Loess Plateau was similar to the current erosion conditions in neighboring regions, where the soil erosion rate now is 8 000 to 10 000 t km^-2 year^-1. After the secondary vegetation restoration, soil erosion was very low; influences of rainfall and slope gradient on soil erosion were small; the vegetation effect on soil erosion was predominant; shallow gully and gully erosion ceased; and sediment deposition occurred in shallow gully and gully channels. In modern times when human activities destroyed secondary forests, soil erosion increased markedly, and erosion rates in the deforested lands reached 10 000 to 24000 t km^-2 year^-1, which was 797 to 1682 times greater than those in the forested land prior to deforestation. Rainfall intensity and landform greatly affected the soil erosion process after deforestation. These results showed that accelerated erosion caused by vegetation destruction played a key role in soil degradation and eco-environmental deterioration in deforested regions.     

Effect of no‐tillage vs. conventional tillage on soil organic matter and nitrogen contents

Abstract

Four treatments (no‐tillage plus subsoiling, no‐tillage, conventional tillage plus subsoiling, and conventional tillage) were continuously in place for 6 yr and a second set of no‐tillage plus subsoiling and conventional plus subsoiling treatments were continuously in place for 3 yr to study the long‐term effects of conventional and no‐tillage corn on soil organic matter (OM) and N contents. Soil samples were taken at random between the rows and in the rows to a depth of 60 cm, in 5‐cm increments to a depth of 30 cm, and then in 15‐cm increments from the 30 to 60‐cm depth for OM and N determination. No‐tillage resulted in A3 and 20% more Kjeldahl N than conventional tillage in the 0 to 5‐cm soil depth after 6 and 3 yr, respectively. after 6 yr, the 0 to 5‐cm depth had 36% more OM in no‐tillage treatments than in conventional tillage treatments, and soil from no‐tillage treatments averaged 27% more OM than the conventional tillage plus subsoiling treatment at the 0 to 15‐cm soil depth.     

Soil‐grinder type effects on grams of soil scooped

Abstract

Soil preparation can affect soil test results. This study was conducted to compare soil‐grinder effects on grams of soil scooped. Soil samples (n=15,000) were ground by two types of soil grinders, a roller and hammer mill, and then the soil was sieved (10‐mesh), and scooped with a one‐gram scoop (0.85 cm³). The contents of the soil scoop were weighed. Grams of soil scooped ranged from 0.4 to 1.8 g for both soil grinders. The bell‐shaped distribution was centered around 0.8 and 1.0 g for the roller‐ and hammer mill‐type grinder, respectively. When the soil was ground by the roller‐type grinder, 85% of the ground soil was retained on a 50‐mesh sieve. In contrast, with the hammer mill grinder, 45% of the soil was retained on a 50‐mesh, 13% retained on a 100‐mesh, and 42% passed a 100‐mesh sieves. The “heavier” soil scoops with the hammer mill grinder could be explained by the fact that the finer soil particles could pack into the voids that the coarse soil particles created. Bray extractable P and ammonium actetate extractable K, Mg, and Ca were increased 11 to 15% by the “heavier” scooping weight. Grams of soil scooped and soil test levels were affected by the type of soil grinder and soil type.     

Effect of dicyandiamide on the form and recovery of 15N‐labeled urea in the delayed flood soil system

Abstract

Dicyandiamide (DCD) is a nitrification inhibitor that has been proposed for use in drill‐seeded rice. Immobilization of fertilizer NH₄ ⁺‐N by soil microorganisms under aerobic conditions has been found to be significantly enhanced in the presence of a nitrification inhibitor. The objective of this laboratory study was to determine if DCD significantly delayed nitrification of urea‐derived N, and if this enhanced immobilization of the fertilizer N in the delayed‐flood soil system inherent to dry‐seeded rice culture. Nitrogen‐15‐labeled urea solution, with and without DCD (1: 9 w/w N basis), was applied to a Crowley silt loam (Typic Albaqualf) and the soil was incubated for 10 weeks in the laboratory. The soil was maintained under nonflooded conditions for the first four weeks and then a flood was applied and maintained for the remaining six weeks of incubation. The use of DCD significantly slowed the nitrification of the fertilizer N during the four weeks of nonflooded incubation to cause the (urea + DCD)‐amended soil to have a 2.5 times higher fertilizer‐derived exchangeable NH₄+‐N concentration by the end of the fourth week. However, the higher exchangeable NH₄+‐N concentration had no significant effect on the amount of fertilizer N immobilized during this period. Immobilization of the fertilizer N appeared to level off during the nonflood period about the second week after application. After flooding, immobilization of fertilizer N resumed and was much greater in the (urea + DCD)‐amended soil that had the much higher fertilizer‐derived exchangeable NH₄ ⁺‐N concentration. Immobilization of fertilizer N appeared to obtain a maximum in the urea‐amended soil (18%) about two weeks after flooding and for the (urea + DCD)‐amended soil (28%) about four weeks after flooding.     

Effect of extractable zinc,phosphorus, and soil ph on zinc concentrations in leaves of field‐grown corn

Abstract

The variability in corn yield responses to applications of Zn fertilizer appears to be associated with several complex soil and climatic factors that affect the availability of endogenous soil Zn to the crop under specific conditions. Among the soil chemical properties that influence availability of endogenous Zn are soil pH, organic matter content, and extractable P. Over a period of several years, soil and plant analysis data were collected from 54 field experiments, field trials, and diagnostic visits to producer's fields. These data were subjected to multiple regression analysis, resulting in an equation: Zn_leaf = 37.14 + 1.513 Zn_st ‐4.04 pH_st ‐ 1.791 ln(P_st/100) where Zn_st, pH_st, and P_st were 0.1N HC1 extractable soil Zn (kg/ha), 1:1 soil‐water pH, and Bray's 1 extractable soil P (kg/ha), respectively. These factors accounted for 67% of variation in leaf Zn, which was a large portion of the variability in Zn_leaf considering that climatic conditions, management levels, and varietal differences were uncontrolled in most instances. Using the previously published critical level in the leaf opposite and below the ear as 17 μg Zn/g, these data can be used to set required soil test levels of Zn at different levels of extractable P and soil pH. Inadequate levels of extractable Zn would range from 2.5 (at pH 6.0, P = 70 kg/ha) to, 9.5 kg/ha (at pH 7.5, P = 420 kg/ha).     

Effect of peat moss‐shrimp wastes compost on the growth of barley (Hordeum vulgare L.) on a loamy sand soil

Abstract

A greenhouse experiment was conducted to determine the effect of peat moss‐shrimp wastes compost on barley (Hordeum vulgare L.) grown on a limed loamy sand soil. A control, four rates of compost applied alone and in combination with three rates of nitrogen, phosphorus, and potassium (NPK) chemical fertilizer were evaluated. Applications of compost to limed soil substantially enhanced the growth of barley over the control. When considering all treatments, the main effect of compost rates on straw yield, numbers of tillers, plant height, and number of ears was more important than that of fertilizer. A significant interaction on barley growth parameter values was obtained with compost and fertilizer rates. A combination of moderate application of compost and fertilizer gave in some instances, more yield than compost or fertilizer applied alone. Nutrient content of barley increased with rate of compost applied to soil over the control. A significant relationship was found between soil organic carbon (C) and straw yield, number of tillers, plant height and number of ears whereas grain yield was correlated with soil total N. Results from this study indicate that peat moss‐shrimp wastes compost could represent a potential means of renovating low fertility sand soils.     

Acid‐soil‐stress influence on mineral‐ion contents of sorghum leaves and juvenile panicles

Sorghum [Sorghum bicolor (L.) Moench cv RTX430, SC214, SC574, SC599, TAM428, and SC326xSC103] were grown on soils of pH 4.2 or 6.2–6.5. Leaf and nonexserted juvenile panicle tissues were collected at 75 days after planting. Fresh and dry weights were measured and element contents [sulfur (S), phosphorus (P), magnesium (Mg), calcium (Ca), potassium (K), zinc (Zn), iron (Fe), and copper (Cu)] were measured by atomic absorption. Significant cultivar differences in ion concentration (μmol/g dry weight) were found. Juvenile panicles had higher ion concentration (μmol/g dry weight) [S, P, Mg, Ca, K, Zn, and Cu) than leaves. Within leaf tissue, ion concentration (μmol/g dry weight) was correlated with tissue water content (g water/g dry weight).     

Effect of Selenium on Magnesium,Iron, Manganese,Copper, and Zinc Accumulation in Corn Treated by Indole‐3‐acetic Acid

In this work, the relationship among accumulation of selenium, auxin, and some nutrient elements [magnesium (Mg²⁺), iron (Fe³⁺), manganese (Mn²⁺), copper (Cu²⁺), zinc (Zn²⁺)] in tissues of roots, mesocotyls, and leaves of Zea mays L. plants was studied. Seeds of maize were cultivated for 4 days in the darkness at 27 °C on moist filter paper, then the individual seedlings were transferred into an aerated solution containing the macro‐ and microelements and were cultivated in a greenhouse for 12 h in the light and 12 h (12‐h photoperiod) in the dark at 25 °C. The seedlings were exposed to the solution containing sodium hydrogen selenite (NaHSeO₃), indole‐3 acetic acid (IAA), or IAA+NaHSeO₃ for approximately 96 h before chemical analysis. The concentration of IAA in the external medium was 10^?4 mol dm^?3, concentration of selenite (NaHSeO₃) was 10^?6 mol dm^?3, and the pH of the medium was 6.5.

The accumulation of the probed elements in seedlings of maize was measured by inductively coupled plasma optical emission spectroscopy (ICP‐OES). It was determined that the selenite and IAA, present in the external medium of growing plants, changed the uptake and accumulation of some cations in tissues of leaves, mesocotyls, and roots. The change of transport conditions of these nutrient elements is probably one of the first observed symptoms of selenium effects on plants.     

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.     

Effect of rock phosphate and superphosphate on crop yield and soil phosphorus test in long‐term fertility plots

Abstract

A long‐term (1968–1987) field study using corn‐soybean in rotation was conducted to compare the effect of rock phosphate (RP) and superphosphate (SP) at two lime levels on crop yield, soil available phosphorus (P) as Bray P‐1 (0.025M HCl + 0.03M NH₄F) and Bray P‐2 (0.1M HCl + 0.03M NH₄F) tests, and on the relationship between crop yield and available P tests. Treatments included a control, application of RP and SP ranging from 12 to 96 kg P₂O₅ ha^‐1 yr^‐1, and combinations of RP with SP or sulphur at various rates. The RP was applied once in 1968 at 8 times the annual rate while SP was applied annually until 1985. Corn and soybean yields increased with P application, more with SP than with RP. Bray P‐l and Bray P‐2 increased linearly with the amount of P applied as SP or RP. A significant correlation (r > 0.64) was found between corn yield and Bray P‐2 at low lime level with both P sources. In contrast, a poor correlation (r < 0.50) was found between soybean yield and soil P tests. Both RP and SP were effective sources of P fertilizers for corn on soils treated with a small amount of lime compared with a large amount of lime. Under low lime the Bray P‐2 accounted for 41% and 66% variability in com yield with applied RP and SP, respectively. On the other hand, Bray P‐1 was only of value when SP was the source of P.     

Use of loss‐on‐ignition to assess soil organic carbon in forest soils

Abstract

Forest floor and mineral soils were collected from 169 conifer and hardwood forested plots across Minnesota, Wisconsin, and Michigan. Regression equations were developed between LOI and organic C for 20% of the samples (n=337), and LOI was then used to predict organic C on all of the samples. Results indicated that LOI is a good estimator of organic C in these soils, but that separate equations were needed for different soil strata. Percent organic C in forest floors was greater in conifer stands compared to hardwood (means of 35.1 and 30.1%, respectively)     

Effect of nitrogen on the growth and photo‐synthetic activity of salt‐stressed barley

Pot experiments were conducted in the greenhouse to study the effect of nitrogen (N) nutrition on photosynthesis and water relations of barley plants under salinity conditions. Nitrogen decreased the sodium (Na) content and increased the potassium (K) content in shoots. The net photosynthetic rate of leaves increased significantly with added N increasing from 0 to 100 mg N/kg soil. The activity of ribulose 1,5 bisphosphate carboxylase (RuBPC_ase) in leaves of high‐salt plants was lower, and in leaves of the low‐salt plants higher than that in control plants. The photosynthetic rate was reduced by sodium chloride (NaCl) and was significantly correlated with total soluble protein per unit leaf area. At each N level, stomatal conductance in leaves was reduced considerably by salt. Proline content of leaves increased with increasing N level. It was higher in leaves of salt‐treated plants than in those of control plants. The osmotic potential of leaves decreased with increasing N applied, and the turgor pressure of high N plants remained higher under salt treatment condition.     

Loss‐on‐ignition as an estimator of soil organic carbon in a‐horizon forestry soils

Abstract

The determination of soil organic matter by wet digestion techniques is a slow and laborious analysis. Loss‐on‐ignition (LOI) provides a simple alternative technique for the estimation of soil organic carbon in non‐calcareous A horizon soils of the Natal midlands and Zululand forestry regions. Using multiple regressional techniques, the relationships between loss‐on‐ignition, Walkley organic carbon and soil texture for 55 soils were determined over a range of ignition temperatures. The relationships hold best for soil samples with relatively low organic carbon contents (< 5%). The optimum temperature for ignition was found to occur at 450°C and resulted in the relationship: Soil organic carbon = 0.284*LOI percent. No advantage is gained through ignition at higher temperatures due to the loss of clay mineral structural water, even if the soil texture is accurately known.     

Effect of different nitrogen‐forms and iron‐chelates on the development of stinging nettle

The development of stinging nettle (Urtica dioica L.) grown on culture solution containing with either ammonium or nitrate ions, or urea, was investigated under iron deficiency conditions, and with added FeEDTA or FeCto. Both seed‐cultured and vegetatively‐cultured stinging nettle plants produced normally developed green shoots when nitrate and 4 μM FeEDTA or FeCto were supplied. Stinging nettle plants were able to utilize Fe‐citrate, Fe‐ascorbate, and Fe‐malate effectively at the same concentration as well. When K3Fe(CN)6 was supplied, which is impermeable to the plasmalemma, and therefore is used to measure the reductive capacity of the roots, stinging nettle plants became chlorotic because the complex was stable at the pH of the culture solution. Urea did not induce chlorosis but inhibited growth. The plants died when ammonium was supplied as a sole N source. Applying bicarbonate and ammonium together prevented the plants from dying, but the plants became chlorotic. Total exclusion of iron from the culture solution resulted in iron‐deficiency stress reactions as has been described for other dicotyledonous plants (Strategy II).     

Effects of coalbed methane‐produced water on sorghum‐sudangrass growth and soil chemical properties

Abstract

Production of methane gas from coal seams generates well water that is slightly to moderately saline. Since land application is a potential method of disposal for this water, a greenhouse study was conducted to evaluate plant response and changes in soil chemical properties resulting from irrigation with coalbed methane‐produced water. The soil was a Montevallo (Typic Dystrochrepts)‐Nauvoo (Typic Hapludults) association located in northern Alabama. Two irrigation methods used in the initial greenhouse test were 1) continuous, irrigation 24 h d^‐1 and 2) intermittent, irrigation for 12 h and off for 24 h. In a second greenhouse test, three irrigation methods were used: 1) continuous, irrigation for 24 h d^‐1, 2) intermittent, irrigation for 12 h and off for 48 h, and 3) irrigation to maintain field capacity, by daily additions of the respective irrigation water. The flow rate for continuous and intermittent irrigation treatments was 3.75 mm h^‐1. In each greenhouse test, 5 levels of salinity were generated by mixing well‐produced water with deionized water to give solutions containing 0, 10, 20, 40, and 100% well‐produced water (specific conductance (second greenhouse test) of 0.2, 1.4, 2.2, 4.4, and 9.3 dS m^‐1, respectively). Corresponding sodium adsorption ratios were 0.1, 27, 36, 55, and 81, respectively. Sorghum‐sudangrass [Sorghum bicolor (L.) Monech] was harvested for forage yields and chemical analysis at 14–30 days after initiation of irrigation treatments. Results from these preliminary short term, greenhouse studies show that coalbed methane produced water that is typical for Alabama (total dissolved solids ≤2000 mg L^‐1) can be applied to highly weathered soils. The results indicate that plant growth of summer annual grasses will be optimized if an irrigation system is used to apply produced water at a rate to maintain soil moisture at or near field capacity.     

Effect of autumn‐olive on the mineral composition of black walnut leaves

Abstract

Nitrogen concentrations were significantly higher in walnut leaves from trees planted with autumn‐olive than in leaves from walnut planted alone, while the reverse was true for potassium. The amount of nitrogen, phosphorus, potassium, calcium, and magnesium based on leaf weight was higher in leaves from walnut trees mixed with autumn‐olive than in leaves from walnut planted alone. The differences in nutrient content between the mixture and walnut alone increased over the sampling period as leaf weights increased proportionately more in the mixture. The increased mobilization of minerals into the leaf is attributed to the increased availability of nitrogen fixed by autumn‐olive and the subsequent uptake by walnut in the mixture. The better nutrition of trees in the mixture compared to walnut planted alone has resulted in better growth and a longer growth period.     

Effects of soil compaction and water‐filled pore space on soil microbial activity and N losses

Abstract

Soil compaction is a significant production problem for agriculture because of its negative impact on plant growth, which in many cases has been attributed to changes in soil N transformations. A laboratory experiment was conducted to study the effect of soil compaction and water‐filled pore space on soil microbial activity and N losses. A hydraulic soil compaction device was used to evenly compress a Norfolk loamy sand (fine‐loamy, siliceous, thermic Typic Kandiudults) soil into 50 mm diameter by 127 mm long cores. A factorial arrangement of three bulk density levels (1.4, 1.6, and 1.8 Mg/m³) and four water‐filled pore space levels (60, 65, 70, 75%) was used. Fertilizer application of 168 kg N/ha was made as 1.0 atom % ¹⁵N as NH₄NO₃. Soil cores were incubated at 25°C for 21 d. Microbial activity decreased with both increasing water‐filled pore space and soil bulk density as measured by CO₂‐C entrapment. Nitrogen loss increased with increasing bulk density from 92.8 to 334.4 g N/m³ soil at 60% water‐filled pore space, for 1.4 and 1.8 Mg/m³, respectively. These data indicate that N loss and soil microbial activity depends not only on the pore space occupied by water, but also on structure and size of soil pores which are altered by compaction.     

Effect of moist‐incubation and microbial inhibition on changes in DTPA‐extractable Mn

Abstract

Effect of incubation and microbial inhibition at field capacity level on changes in DTPA‐extractable Mn in acidic, neutral, and alkaline soils was examined. Incubation decreased and microbial inhibition increased the level of Mn in soils with high pH (>5.7) and high microbial activity. The change was apparently partially associated with microbes since the level of Mn did not change in soils with low microbial activity and/or low pH.