Adequate Plant Growth Research Articles

Chemical Relaxation and Double Layer Model Analysis of Boron Adsorption on Alumina

AbstractBoron is a plant nutrient essential for adequate plant growth, yet the range between B deficiency and toxicity levels is rather narrow. Boron adsorption reactions with soil components, particularly sesquioxides, most often regulate the amount of B in the soil solution. The reaction mechanisms of B adsorption on oxides have not been fully characterized, however. Pressure‐jump relaxation experiments were conducted to measure the rates and determine the reaction mechanism for B adsorption on an alumina (γ‐Al2O3) surface from B(OH)3‐B (OH)−4 solutions. Relaxation times (τ) were measured from pH 7.0 to 9.7 in alumina suspensions with 0.012 mol L−1 total B. A plot of τ−1 vs. B(OH)−4 plus surface site concentration obtained from the triple layer model (TLM) assuming inner sphere B(OH)−4 adsorption yielded an adsorption rate constant (kintf) of 3.3 × 105 L mol−1 s−1 and a desorption rate constant (kintr) of 1.8 × 10−3 L mol−1 s−1. The ratio kintf/kintr yielded an equilibrium constant (log KintKIN) of 8.26, in agreement with the intrinsic equilibrium constant for B(OH)−4 adsorption (log KintBIS = 7.69) obtained from adsorption isotherms. Four additional surface complexation models were tested for their ability to model both the equilibrium and kinetic data simultaneously: the constant capacitance model, the diffuse layer model, a Stern model variant, and the TLM assuming outer sphere B(OH)−4 adsorption. Only the TLM, assuming both B(OH)3 and B(OH)−4 were adsorbed via ligand exchange on neutral surface sites, was successful. The TLM indicated that B(OH)−4 is the predominant adsorbed species throughout the pH range 7.0 to 10.8.

THE NATURE OF URBAN SOILS: THEIR PROBLEMS AND FUTURE

Summary Urban soils are those that exist in or that are designed for the urban environment and that exhibit anthropeic characteristics. In many instances these characteristics present unfavorable conditions for plant growth. These conditions include: the loss of structure leading to compaction and its attendant decreased aeration, drainage, water- holding capacity and infiltration, and resistance to root penetration; interrupted organic matter cycling; and spatial and vertical variability which decreases their predictable nature. Our imperfect knowledge and expertise are challenged to modify or design them to meet the requirements of at least adequate plant (mainly tree) growth. Future effort requires more detailed soil specifications, greater sensitivity to environmental impact or sustainability by the use of soil substitutes, and more research on tree water utilization and rooting requirements.

Rapid assessment of the rate of nitrogen immobilisation in organic components of potting media: II. Nitrogen drawdown index and plant growth

Abstract In several experiments, cabbage seedlings were grown in soilless potting media produced using a range of aged and composted pinebarks, peat and sawdusts. Their growth was compared with the Nitrogen Drawdown Indexes (NDI) of the media, measured by a standard method previously reported. Growth was highly correlated with NDI when N was applied via pre‐plant additions and/or liquid drenches. Aged pinebarks and composted hardwood sawdusts, with high N immobilisation potential, have NDI values near zero and consume N at about 300 mg/L each week. Adequate plant growth is difficult to obtain in these media. Media with NDI values of around 0.5 consume about 40 mg/L N each week. Pre‐plant amendment with N equivalent to that in 0.5–1.0 g/L NH4NO3 is desirable and weekly feeding with a solution containing 200–400 mg/L N will give maximum growth rate. Weekly feeding with solutions containing 100–150 mg/L N provides sufficient N for excellent plant growth in peat‐based media, whose NDI values are 0.95–1.0.

Heavy metal uptake by blue grama growing in a degraded semiarid soil amended with sewage sludge

Sewage sludge application to semiarid grassland may represent a beneficial means of utilizing this waste product for restoration of degraded sites. Consequently, dried municipal sewage sludge was applied at three rates (22.5, 45, and 90 Mg ha−1) to a degraded semiarid grassland soil in order to determine the effects of sludge amendments on forage productivity, soil heavy metal content, and metal uptake by blue grama (Bouteloua gracilis).Soil and plant properties in control and amended plots were measured after 1, 2, and 5 growing seasons.Soil nutrients increased linearly with increased sludge application in the first two growing seasons. Consequently, forage quality and total production of blue grama improved significantly over the unamended control as the tissue levels of N, P, K, and crude protein increased. Cadmium and Pb in the sludge-treated plots did not increase significantly over the control after 1 and 2 growing seasons. Levels of DTPA-extractable soil micronutrients (Cu, Fe, Mn, Zn) increased linearly with increased sludge application rate to soil concentrations recommended for adequate plant growth. Soil N, P, and K concentrations remained higher in the sludge-amended soils after 5 growing seasons, while Cu and Cd increased to slightly above desireable limits as the soil pH decreased to 7.4 and 7.0 in the 45 and 90 Mg ha−1 treatments, respectively. However, with the exception of Mn which remained within desirable limits, metal concentrations (including Cu and Cd) in blue grama tissue were not significantly different from the control treatment after five growing seasons. Based on soil and plant tissue metal concentrations, it appears that sludge applied at rates between 22.5 and 45 Mg ha−1 will maintain the most favorable nutrient levels coupled with significant improvements in forage production in this semiarid grassland environment.

Sewage Sludge Effects on Soil and Plant Quality in a Degraded, Semiarid Grassland

AbstractA major problem affecting grassland productivity in the semiarid southwestern USA is the low quantity of soil organic matter and plant‐available N. In this study, dried, anaerobically digested sewage sludge was applied at three rates (22.5, 45, and 90 Mg ha−1) to a degraded semiarid grassland site to determine the effects of sludge on soil chemical and heavy metal properties, and vegetative yields and quality over two growing seasons. Most nutrients, including soil N, P, and K, increased linearly as a result of sludge amendment. Soil pH decreased linearly from 7.8 to 7.4 with the application of sludge after the second growing season, but did not significantly increase the solubility of soil heavy metals (Pb and Cd). On the other hand, the levels of DTPA‐extractable soil micronutrients (i.e., Cu, Mn, Zn) increased linearly with sludge rates to levels recommended for adequate plant growth. Total herbaceous plant yields increased significantly with sludge amendment, particularly at the 45 Mg ha−1 sludge rate, as compared with the control treatment. Blue grama [Bouteloua gracilis (H.B.K.) Lag. ex Steud.] yields increased two‐ to threefold in amended plots over the unamended control after two growing seasons. The forage quality of blue grama, galleta [Hilaria jamesii (Torr.) Benth.], and bottlebrush squirreltail [Sitanion hystrix (Nutt.) J.G. Sm.], improved significantly as the levels of tissue N, P, and K, and crude protein increased linearly with sludge application. As expected, levels of Cd and Pb in all plant tissues did not increased significantly as a result of sludge amendment. All micronutrients increased to acceptable levels in deficient plant tissues. Sewage sludge applied at the rate of 45 Mg ha−1 gave the most favorable soil and vegetation results.

Revegetation in an iron ore mine - Nutrient requirements for plant growth and the potential role of vesicular arbuscular (VA) mycorrhizal fungi

Revegetation after iron-ore mining in the Pilbara region of Australia is difficult because of the harsh climate and because the material to be revegetated is likely to have poor fertility and low microbial activity. In this work we defined the infectivity of VA mycorrhizal fungi in local soils and mine materials, and then the nutrient requirements for adequate plant growth in low-grade ore. Finally, we tested the hypothesis that addition of phosphorus to low-grade ore, and inoculation with VA mycorrhizal fungi, increases the growth of Acacia pyrijolia. The VA mycorrhizas were formed only in soil collected from sites dominated by Triodia pungens. A. pyrifolia nodulated only in soil from sites dominated by A. aneura. In low-grade ore, phosphorus deficiency was the major limitation to plant growth. Inoculation with a Glomus sp. resulted in up to 70% increases in dry matter production at low rates of phosphorus. The response to phosphorus or inoculation with VA mycorrhizal fungi was limited by nitrogen deficiency.

Effects of ammonium sulfate aerosols on vegetation—I. Chamber design for long duration exposures

A plant growth chamber has been constructed to expose a large number of plants to a uniformly distributed concentration of submicrometer aerosols of known particle size distribution and chemistry for periods up to 3 weeks. The chamber design with features controlled externally provides regulation of wind velocity, temperature, relative humidity, air exchange, lighting, irrigation and aerosol injection. This facility provides adequate plant growth in the presence and absence of submicrometer ammonium sulfate aerosols of known particle size distribution in order to determine deposition rates, mode of entry and effects of submicrometer aerosols on vegetation.

Response of okra plants to root and foliar applied boron.

Abstract The response of okra plants (Hibiscus esculentus) to root‐and foliar‐applied B at 0, 2 and 4 ppm was investigated in solution culture. Root‐B application higher than 2 ppm resulted in severe root burn and toxicity in the plants, whereas foliar‐B application up to 4 ppm produced adequate plant growth. Chlorophyll and carotene content of the leaves, flower number, stem diameter, plant height and dry matter production were drastically reduced at high root‐applied B when compared to the foliar treatments. Significant negative correlation between root‐applied B and plant height, stem diameter, leaf and flower number was established. Except for a significant negative correlation with leaf number, all other growth components were positively correlated with foliar application of B. At 2 ppm B, leaf‐B, ‐P, ‐K and ‐Ca were higher at the root‐B than at the foliar‐B treatments. Foliar application of B was superior to root‐application as was observed in the healthy growth of the okra plant.

SOME EFFECTS OF FERTILIZATION ON THE YIELD, BOTANICAL AND CHEMICAL COMPOSITION OF IRRIGATED GRASS AND GRASS-CLOVER PASTURE SWARDS

In an irrigated pasture experiment on Vancouver Island, on a soil deficient in available nitrogen and potassium but apparently containing sufficient available phosphorus, calcium and magnesium for adequate plant growth, an irrigated Ladino clover-grass mixture greatly outproduced a grass mixture on a forage, protein and mineral nutrient yield basis. In order to attain even a moderate yield with a grass mixture, heavy fertilization with nitrogen and potassium was necessary. Nitrogen fertilization was not essential to high yields with the Ladino clover-grass mixture. Nitrogen fertilization tended to decrease the per cent Ladino clover and the protein and calcium content in the clover-grass forage and increased the protein content of the grass herbage. The calcium content of the grass herbage was decreased by nitrogen fertilization. The phosphorus and magnesium contents of the clover-grass and grass herbage were not appreciably altered by nitrogen fertilization. Decreasing the time interval between nitrogen applications resulted in a more even production of dry matter over the growing season but did not increase the total seasonal yield. Potassium fertilization increased the yield of both mixtures and increased the per cent clover in the grass-clover sward. Multi-annual potassium applications were required for the elimination of plant potassium deficiency symptoms and the applied potassium was quickly absorbed by the plants. Grass herbage contained more potassium, slightly more phosphorus and less calcium, magnesium and nitrogen than grass-clover herbage.