Showing papers by "Keith C. Cameron published in 1998"

Nitrate leaching from dairy shed effluent and ammonium fertiliser applied to a free‐draining pasture soil under spray or flood irrigation

Abstract: The potential for contamination of groundwater by dairy shed effluent (DSE) and ammonium N fertiliser (NH4CI) was assessed by measuring nitrate leaching from 16 large soil lysimeters (80 cm diam. × 120 cm depth). Each lysimeter contained an undisturbed monolith of Templeton fine sandy loam (Udic Ustochrept) located in Canterbury, New Zealand, with established perennial ryegrass (Lolium perenne) and white clover (Trifolium repens) pasture plants. DSE and NH4CI were applied at 400 kg N ha−1 yr−1, in two split applications of 200 kg N ha−1. During the summer, each lysimeter received either spray (50 mm mo−1) or flood (100 mm mo−1) irrigation. During the winter, the natural rainfall received was supplemented with simulated rainfall in order to reach the 75th percentile of local rainfall records for the winter period. The concentration of nitrate in the leachate reached 5 mg N l−1 under both flood and spray irrigation following the first N fertiliser application (Dec 1995), but did not increase above ...

Effects of spent mushroom substrate on soil chemical conditions and plant growth in an intensive horticultural system: a comparison with inorganic fertiliser

Abstract: Between November 1991 and 1993, 4 consecutive vegetable crops (sweetcorn, cabbage, potato, and cabbage) were grown in Lincoln, New Zealand. The treatments included spent mushroom substrate (SMS, a by-product of the mushroom industry) applications before each crop at rates of 0, 20, 40, or 80 t/ha (moist), both with and without 1 rate of inorganic fertiliser for each crop (120-338, 40-100, 53-100, and 60-114 kg/ha, respectively, of nitrogen, phosphorus, potassium, and sulfur). SMS applications caused a rapid increase in soil inorganic N concentration, but after this it had a variable effect. There was some evidence of N immobilisation following initial SMS applications of 20 t/ha. SMS applications increased both soil pH and CEC, whereas inorganic fertiliser decreased both. Sweetcorn and cabbage yields were increased by SMS when inorganic fertiliser was not used, and potato yield was increased irrespective of fertiliser use (i.e. yield increases of 38%, 82-96%, and 26-46%, respectively, for sweetcorn cob, cabbage head, and potato tuber fresh yields). Inorganic fertiliser increased crop yields by a greater amount than SMS. A lack of soil inorganic N was the major limitation to crop growth following SMS applications, so crops may require additional N with SMS.

The fate of potassium, calcium, and magnesium in simulated urine patches on irrigated dairy pasture soil

Abstract: A lysimeter study was carried out at Lincoln University, Canterbury, New Zealand from July 1990 to July 1991 to determine the fate of potassium (K), calcium (Ca), and magnesium (Mg) in urine patches on an irrigated dairy pasture soil (Templeton silt loam). Five undisturbed monolith lysimeters (800 mm diam. × 1200 mm depth) were extracted from an established ryegrass/white clover pasture. The lysimeters were installed in an underground lysimeter facility, where a 2 litre solution of synthetic urine, containing the equivalent of 55 g m−2 of K, was applied evenly to the surface of each lysimeter (c. 0.5 m2) to simulate a dairy cow urination event. No Ca or Mg was applied in the urine. During the following year, leachate composition and pasture yields from each lysimeter were determined. Twenty percent (10.76 g m−2) of the urine‐applied K was retained within the exchangeable fraction in the top 0–5 cm depth of soil. Total leaching losses of K during the experiment were negligible (0.99 g m−2 yr−1), a...

Inorganic-N release from spent mushroom compost under laboratory and field conditions

Abstract: Inorganic-N release from soil amended with spent mushroom compost (SMC), a by-product of mushroom production, was measured in three open laboratory incubations (25–30°C) and in field lysimeters. Rates of SMC application to the soil were up to 80 t ha −1 equivalent (0.84% dry weight in the laboratory). SMC contained 1.8% N of which 94% was organic, and had a C-to-N ratio of 17. Small amounts of inorganic-N were leached from SMC in the first incubation (3–18% of that applied). Trends in the data suggested that N in the SMC was initially immobilized in the 20 and 40 t ha −1 treatments, as shown by modelling using a negative first order exponential term; it was then slowly mineralized according to zero order kinetics. The laboratory optimized model of inorganic-N loss, when modified to account for field soil temperatures, estimated a similar amount of inorganic-N loss as was observed in the field. The century model overestimated inorganic-N leaching from SMC in the laboratory and underestimated inorganic-N leaching in the field. Fertilizer, containing N, P, K and S, reduced the net amount of inorganic-N recovered from SMC–soil mixtures. The rate of inorganic-N leaching from mushroom compost was considerably slower than from glycine or chicken litter applied at the same N rate. The sterilants applied to mushroom compost during mushroom production and compost sterilization had little effect on the rate of inorganic-N leached from the compost; however, hypochlorite and formaldehyde caused a small increase and decrease respectively in the cumulative amount of inorganic-N leached from mushroom-compost-amended soil. The slow rate of release of inorganic-N from SMC-amended soil is predominantly the result of the slow mineralization of recalcitrant organic-N in SMC.

Nitrogen mineralisation rates from soil amended with dairy pond waste

Abstract: An open incubation and leaching study was conducted under controlled temperature (25°C) and moisture conditions to measure the N mineralisation rate in soil amended with dairy pond sludge. The dairy pond sludge was applied at 3 different rates equivalent to 0, 200, and 400 kg N/ha. The incubation was conducted at 3 different soil moisture potentials (0, -3, and -13 kPa). Following each 2-week period of incubation, the soil was leached with 2 pore volumes of deionised water to remove the mineralisation products. Mineralisation products in the leachate and enzyme activities, microbial biomass C and N, pH, and water-soluble C in the soil were determined. The incubation lasted 18 weeks. Rapid release of nitrate occurred during the first 6 weeks of incubation, followed by a slow release over the remainder of the incubation period. Although the total amount of N released in the 200 kg N/ha treatment (169 mg N/kg soil) was less than in the 400 kg N/ha treatment (206 mg N/kg soil), when expressed as a percentage of the organic N applied, the amount of N released at the lower rate (18·4%) was greater than that at the higher rate of sludge treatment (13·0%). Rapid nitrification decreased the soil leachate ammonium concentration and the soil pH. Soil microbial biomass, water-soluble C, and deaminase activity were significantly increased after the addition of dairy pond sludge. The increase in soil microbial biomass observed was probably due to the increased water-soluble C and nutrients that stimulated the soil microbial growth. The rapid N release and nitrification rates observed were attributed to the low C : N ratio (12·7), high ammonium content (145 mg N/kg) of the dairy pond sludge used, and the optimum moisture and temperature conditions. The narrow range of soil water potential conditions did not have any significant effect on N release rate or amount.

Effects of spent mushroom substrate on soil physical conditions and plant growth in an intensive horticultural system

Abstract: A 2-year field trial determined the influence of applying spent mushroom substrate (SMS) on soil physical properties and the growth of 4 consecutive vegetable crops (sweetcorn, cabbage, potato, cabbage) Treatments comprised 0, 20, 40, and 80 t/ha of moist SMS, both with and without inorganic fertiliser, applied to each crop, giving a range of SMS rates up to 320 t/ha SMS improved the environment for plant root growth by decreasing soil bulk density (by 0· 05-0·25 g/cm 3 at 100 mm depth), increasing aggregate stability (by 13-16%), reducing clod and surface crust formation (by 16-31 and 18-94%, respectively), increasing the infiltration rate (by 130-207 mm/h), increasing the water content of the soil (by 0-7% w/w), and reducing diurnal temperature changes Some of these changes were not evident until repeated applications of 80 t/ha SMS had been made Soil physical properties were related to crop yield, and soil physical properties’ principal components were related to crop principal components using regression analysis (r2 of 0·20-0·60 and 0·16-0·54, respectively) The soil physical properties that had the most influence on plant growth were specific to each crop and included bulk density, water content, surface crust cover, infiltration rate, and aggregate size distribution Soil physical properties had a large influence on the potato yield irrespective of fertiliser use and on both cabbage crop yields when fertiliser was not used, but not on the sweetcorn yield (the first crop to be grown) The effect of changing soil physical properties on plant growth was most apparent when fertiliser was not used This was because the improved physical properties increased plant yield (at least in part) because of increased plant nutrient uptake