Partitioning of olive oil antioxidants between oil and water phases.

The partition coefficient (K(p)) of the natural phenolic antioxidant compounds in the olive fruit between aqueous and olive oil phases was determined. The antioxidants of olive oil are either present in the olive fruit or formed during the olive oil extraction process. The antioxidants impart stability to and determine properties of the oil and are valuable from the nutritional point of view. The olive oil antioxidants are amphiphilic in nature and are more soluble in the water than in the oil phase. Consequently, a large amount of the antioxidants is lost with the wastewater during processing. The determination of antioxidants was performed using HPLC, and the K(p) was estimated to be from as low as 0.0006 for oleuropein to a maximum of 1.5 for 3,4-DHPEA-EA (di-hydroxy-phenyl-ethanol-elenolic acid, oleuropein aglycon). Henry's law fitted very well to the experimental data. The partition coefficients were also estimated by applying the activity coefficients of the antioxidants in the two phases using a predictive group contribution method, the UNIFAC equation. The K(p) values estimated with UNIFAC method were of the same order of magnitude but varied from the experimental values. Nevertheless, this method may be a rough predictive tool for process optimization or design. Because the K(p) values were very low, some changes in the process are recommended in order to achieve a higher concentration of antioxidants in the oil. A temperature increase may lead to increasing the partition coefficient. Also, limiting the quantity of water during oil extraction could be a basis for designing alternative processes for increasing the antioxidant concentration in the olive oil.     

Earthworm burrowing in laboratory microcosms as influenced by soil temperature and moisture

Earthworm burrows contribute to soil macroporosity and support diverse microbial communities. It is not well known how fluctuations in soil temperature and moisture affect the burrowing activities of earthworms. The objective of this experiment was to evaluate the maximum depth and length of burrows created by the endogeic earthworm Aporrectodea caliginosa (Savigny) and the anecic earthworm Lumbricus terrestris L. for a range of temperatures (5–20 °C) and soil water potentials (−5 and −11 kPa). The laboratory microcosm was a plexiglass chamber (45 cm high, 45 cm wide) containing 0.14 m² of pre-moistened soil and litter, designed to house a single earthworm for 7 days. Earthworm mass, surface casting and burrowing activities were affected significantly by soil temperature, moisture and the temperature×moisture interaction. Burrow length and maximum burrow depth increased with increasing temperature, but there was less burrowing in wetter soil (−5 kPa) than drier soil (−11 kPa). Weight gain and surface casting, however, were greater in soil at −5 kPa than −11 kPa. Our results suggest more intensive feeding and limited burrowing in wetter soil than drier soil. Earthworms inhabiting the non-compacted, drier soil may have pushed aside particles without ingesting them to create burrows. The result was that earthworms explored a larger volume of soil, deeper in the chamber, when the soil was drier. How these burrowing activities may affect the community structure and activity of soil microorganisms and microfauna in the drilosphere remains to be determined.     

吸附反应时间对潮土中除草剂阿特拉津吸附行为的影响

A batch experiment was performed to investigate nonequilibrium adsorption behavior of atrazine （2-chloro-4-ethylamino-6-isopropylamlno-1,3,5-triazlne） on a fluvo-aquic soil. The amount of atrazine sorbed increased with increasing adsorption contact periods. For a range of initial atrazlne concentrations, the percentage of atrazine sorbed within 24 h ranged from 24% to 77% of the observed total amount sorbed for the longest contact period; when adsorption contact periods were more than 72 h, the deviations in curves fitted using a nonlinear Freundllch equation gradually became less. The opposite trend was observed for the atrazine concentrations in solution. The effect of adsorption contact periods on atrazine adsorption behavior was evaluated by interpreting the temporal variations in linear and nonlinear Freundlich equation parameters obtained from the phase-distribution relationships. As the adsorption contact period increased, the nonlinear Freundlich capacity coefficient kf showed a significant linear increase （r^2 = 0.9063, P 〈 0.001）. However, a significant negative linear correlation was observed for the nonlinear coefficient n, a dimensionless parameter （r^2 = 0.5666, P 〈 0.05）. Furthermore, the linear distribution coefficient kd ranged from 0.38 to 1.44 and exhibited a significant linear correlation to the adsorption contact period （r^2 = 0.72, P 〈 0.01）. The parameters kf and n obtained from a time-dependent isotherm rather than the distribution coefficient kd estimated using the linear Freundlich equation were more appropriate to predict the herbicide residue in the field and thus more meaningful for environmental assessment.     

Senescence in sweet corn as influenced by phosphorous nutrition 1

Nutrient availability can affect the onset of senescence. Phosphate‐phosphorus (P) was added at the recommended and five times the recommended level to a Bernow fine‐loamy, siliceous, thermic Glossic Paleudalf soil at Lane, OK. Senescence in stalk and shank internodes and cobs was rated in shrunken‐2 sweet corn (Zea mays L.) cultivars at various developmental stages. Plant dry weight was determined at fresh market harvest. Stalk internode senescence rating increased through harvest. The internode subtending the ear node was almost completely senescent at anthesis. There were statistical, but likely not biologically important, differences in stalk internode senescence between cultivars. Increased P occasionally increased stalk internode senescence rating and reduced plant dry weight. Increased P either decreased, or had no effect on, shank internode or cob senescence.     

Rice Straw-Derived Biochar Properties and Functions as Cu(Ⅱ) and Cyromazine Sorbents as Influenced by Pyrolysis Temperature

In this study, biochars from rice straw(Oryza sativa L.) were prepared at 200–600?C by oxygen-limited pyrolysis to investigate the changes in properties of rice straw biochars produced at different temperatures, and to examine the adsorption capacities of the biochars for a heavy metal, copper(Ⅱ)(Cu(Ⅱ)), and an organic insecticide of cyromazine, as well as to further reveal the adsorption mechanisms.The results obtained with batch experiments showed that the amount of Cu(Ⅱ) adsorbed varied with the pyrolysis temperatures of rice straw biochar. The biochar produced at 400?C had the largest adsorption capacity for Cu(Ⅱ)(0.37 mol kg-1) among the biochars,with the non-electrostatic adsorption as the main adsorption mechanism. The highest adsorption capacity for cyromazine(156.42 g kg-1) was found in the rice straw biochar produced at 600?C, and cyromazine adsorption was exclusively predominated by surface adsorption. An obvious competitive adsorption was found between 5 mmol L-1Cu(II) and 2 g L-1cyromazine when they were in the binary solute system. Biochar may be used to remediate heavy metal- and organic insecticide-contaminated water, while the pyrolysis temperature of feedstocks for producing biochar should be considered for the restoration of multi-contamination.     

Relationships between soil aggregation and mycorrhizae as influenced by soil biota and nitrogen nutrition

 The effect of the form of N nutrition on soil stability is an important consideration for the management of sustainable agricultural systems. We grew soybean [Glycine max (L.) Merr.] plants in pot cultures in unsterilized soil, and treated them by (1) inoculating them with Bradyrhizobium japonicum, fertilizing with (2) nitrate or (3) ammonia, or (4) by providing only minimum N amendment for the controls. The soils were sampled at 3-week intervals to determine changes in water-stable soil aggregates (WSA), soil pH, the development of roots, arbuscular mycorrhizal (AM) soil and root colonization, and selected functional groups of soil bacteria. The soil fauna was assayed at the end of the experiment (9 weeks). WSA was correlated positively with root and AM soil mycelium development, but negatively with total bacterial counts. Soil arthropod (Collembola) numbers were negatively correlated with AM hyphal length. Soils of nodulated and ammonia-fertilized plants had the highest levels of WSA and the lowest pH at week 9. Sparse root development in the soils of the N-deficient, control plants indicated that WSA formation was primarily influenced by AM hyphae. The ratio of bacterial counts in the water-stable versus water-unstable soil fractions increased for the first 6 weeks and then declined, while counts of anaerobic bacteria increased with increasing WSA. The numbers of soil invertebrates (nematodes) and protozoans did not correlate with bacterial counts or AM soil-hyphal lengths. Soil pH did not affect mycorrhiza development, but actinomycete counts declined with decreasing soil pH. AM fungi and roots interacted as the factors that affect soil aggregation, regardless of N nutrition. Received: 20 December 1997     

Hydrogen oxidation activities in soil as influenced by pH,temperature, moisture,and season

Summary Hydrogen oxidation in soil was measured at low (1 ppmv) and high (300 ppmv) H₂ concentrations to distinguish between the activities of abiontic soil hydrogenases and Knallgas bacteria, respectively. The two activities also showed distinctly different pH optima, temperature optima, and apparent activation energies. The pH optima for the soil hydrogenase activities were similar to the soil pH in situ, i.e., pH 8 in an slightly alkaline garden soil (pH 7.3) and pH 5 in an acidic cambisol (pH 4.6–5.4). Most probable number determinations in the alkaline acidic soils showed that Knallgas bacterial populations grew preferentially in neutral or acidic media, respectively. However, H₂ oxidation activity by Knallgas bacteria in the acidic soil showed two distinct pH optima, one at pH 4 and a second at pH 6.4–7.0. The soil hydrogenase activities exhibited temperature optima at 35–40°C, whereas the Knallgas bacteria had optima at 50–60°C. The apparent activation energies of the soil hydrogenases were lower (11–23kJ mol^-1) than those of the Knallgas bacteria (51–145 kJ mol^-1). Most of the soil hydrogenase activity was located in the upper 10 cm of the acidic cambisol and changed with season. The seasonal activity changes were correlated with changes in soil moisture and soil pH.     

Tomato fruit quality as influenced by the interactions between agricultural techniques and harvesting period

Tomato (Solanum lycopersicum Mill) is an important crop in terms of its economic and nutritional value. Many factors, including cultivar, climate, geography, geochemistry, and agricultural practice, can affect its nutrient concentrations. An HJ‐biplot study was performed to examine the effects of cultivar (Dorothy, Boludo, Dominique, Thomas, and Dunkan), agricultural practices, climatic factors, and their interactions. Significant differences were analyzed using a one‐way ANOVA. All samples were collected and assayed at the same degree of ripeness. In the conventional and organic tomato samples, those harvested from December to April had the highest concentrations of fructose, glucose, citric acid, malic acid, ascorbic acid, protein, Na, and Mg, while those harvested in October had the highest concentrations of lycopene and hydroxycinnamic acid. There were high concentrations of Ca, P, Zn, and Cu in the no‐soil tomatoes. Conventional and organic cultivation practices showed similar results with respect to the collection period, both presenting high organic compound concentrations, while high mineral concentrations seemed to correspond to the no‐soil practice. No clear pattern was observed among the different cultivars, perhaps due to all the samples having been collected at the same degree of ripeness.     

Dynamics of methanogenesis and methanotrophy in tropical paddy soils as influenced by elevated CO2 and temperature interaction

Response of methanogenesis and methanotrophy to elevated carbon dioxide (CO₂) could be affected by changes in soil moisture content and temperature. In soil microcosms contained in glass bottles and incubated under laboratory conditions, we assessed the impact of elevated CO₂ and temperature interactions on methanogenesis and methanotrophy in alluvial and laterite paddy soils of tropical origin. Soil samples were incubated at ambient (370 μmol mol⁻¹) and elevated (600 μmol mol⁻¹) CO₂ concentrations at 25, 35 and 45 °C under non-flooded and flooded conditions for 60 d. Under flooded condition, elevated CO₂ significantly increased methane (CH₄) production while under non-flooded condition, only marginal increase in CH₄ production was observed in both the soils studied and the increase was significantly enhanced by further rise in temperature. Increased methanogenesis as a result of elevated CO₂ and temperature interaction was mostly attributed to decreased soil redox potential, increased readily mineralizable carbon, and also noticeable stimulation of methanogenic bacterial population. In contrast to CH₄ production, CH₄ oxidation was consistently low under elevated CO₂ concentration and the decrease was significant with rise in temperature. The low affinity and high affinity CH₄ oxidation were faster under non-flooded condition as compared to flooded condition. Admittedly, decreased low and high affinity CH₄ oxidation as a result of elevated CO₂ and temperature interaction was related to unfavorable lower redox status of soil and the inhibition of CH₄-oxidizing bacterial population.     

Relationship between lead uptake by lettuce and water-soluble low-molecular-weight organic acids in rhizosphere as influenced by transpiration

The relationship between Pb uptake by leaf lettuce ( Lactuca sativa L.) and water-soluble low-molecular-weight organic acids (LMWOAs) in rhizosphere, as influenced by transpiration (high and low), has been studied. Studies were carried out by culturing lettuce plants grown for 2 weeks in pots filled with quartz sand mixed with anion-exchange resin and then for 30 days in a greenhouse. The potted lettuce plants were subjected to stress by the addition of Pb(NO 3) 2 solutions (100, 200, and 300 mg of Pb L (-1)) and by high and low transpiration treatments for another 10-day period. Blank experiments (without addition of Pb(NO 3) 2 solutions to the pots) were also run. There were no significant differences in the growth of the plants with the addition of Pb(NO 3) 2 solutions in either of the transpirations studies. Uptake of Pb by the shoots and roots of the plants was found to be proportional to the concentration of Pb solutions added, and more accumulation was observed in the roots than in the shoots at the end of days 3 and 10. High transpiration caused more Pb uptake than did low transpiration. One volatile acid (propionic acid) and nine nonvolatile acids (lactic, glycolic, oxalic, succinic, fumaric, oxalacetic, d-tartaric, trans-aconitic, and citric acids) in rhizosphere quartz sand or anion-exchange resin were identified and quantified by gas chromatography analysis with a flame ionization detector. The amount of LMWOAs in rhizosphere quartz sand or anion-exchange resin increased with higher amounts of Pb in quartz sand solution and also with longer duration of the study. The total quantities of the LMWOAs in the rhizosphere quartz sand or anion-exchange resin were significantly higher under high and low transpiration with a 300 mg of Pb L (-1) solution addition at the end of day 10. Compared with our previous related studies (published work), the present study shows that the presence of LMWOAs in rhizosphere does not significantly affect Pb uptake by lettuce plants under high and low transpiration. A physiological mechanism of the roots of lettuce plants governing the relationship between Pb contamination level and quantity of water-soluble LMWOAs in rhizosphere quartz sand and resin, as influenced by transpiration, was proposed.     

Tomato growth and nutrient uptake patterns as influenced by nitrogen form and light intensity 1

Tomato plants were grown in sand culture with NH₄ or NO₃ forms of N and at two levels of light. Plants were harvested at 0, 5, 9, or 12 days after starting treatments. NH₄‐N nutrition reduced growth, suppressed K, Ca, and Mg accumulation in shoot, increased P and N content and markedly reduced K, Ca, and Mg uptake per unit of root surface. Reduced light level decreased the toxic effects of NH₄ and markedly decreased NH₄ accumulation in shoots.     

Antioxidant capacity in cranberry is influenced by cultivar and storage temperature

Ten cranberry (Vaccinium macrocarpon Aiton) cultivars were evaluated for oxygen radical absorbance capacity (ORAC), anthocyanins, and total phenolics contents after three months of storage at 0, 5, 10, 15, and 20 degrees C. The antioxidant capacity of cranberry was affected by cultivars and storage temperatures. Among the 10 cranberry cultivars used in this study, Early Black, Crowley, and Franklin had higher antioxidant capacities than the other cultivars. ORAC values, anthocyanins, and total phenolics contents increased during storage. The highest increases in antioxidant activity, anthocyanin, and phenolics contents occurred at 15 degrees C storage. Fruit stored at 20 degrees C had lower ORAC values than those stored at 15 degrees C. A positive relationship existed between ORAC values and anthocyanin or phenolic content in all 10 cranberry cultivars at different storage temperatures.     

Solubility of soil phosphorus as influenced by urea

The objective of this study was to investigate possible ways of mobilizing residual fertilizer P as a result of local pH elevation caused by urea hydrolysis. The response of water-soluble P (P_w) and dissolved organic C (DOC) to urea hydrolysis was monitored in three cultivated soils and at two P levels for up to 127–135 d and compared with corresponding changes in soils limed with Ca(OH)₂. Hydrolysis of urea was complete in 8–15d during which soil pH increased by 1–1.5 units at the maximum. Subsequently, the pH decreased to or below the original level owing to nitrification. Mobilization of soil P was enhanced substantially in parallel with the increase in pH, the peak P_w occurring simultaneously with the highest pH value. In all urea-treated soils, P_w remained at an elevated level for at least 60d. As compared to urea, elevation of soil pH with Ca(OH)₂ had only a minor and inconsistent influence on P_w. In mobilization of soil P, the urea-induced increase in pH and a simultaneous production of NH₄⁺ ions proved to be superior to liming with Ca(OH)₂. It was hypothesized that when an acid soil is amended with urea, phosphate is first displaced by OH^? ions, resulting in elevated solution P concentrations. A simultaneous dissolution of organic matter contributes to the persistence of high P concentration by competition for sorption sites on Fe and Al oxides, and thus retards the resorption of P.     

Tillering,nutrient accumulation,and yield of winter wheat as influenced by nitrogen form 1

When grown with mixtures of nitrate‐nitrogen (NO₃‐N) and ammonium‐nitrogen (NH₄‐N) (mixed N) spring wheat (Triticum aestivum L.) plants develop higher order tillers and produce more grain than when grown with only NO₃. Because similar work is lacking for winter wheat, the objective of this study was to examine the effect of N form on tillering, nutrient acquisition, partitioning, and yield of winter wheat. Plants of three cultivars were grown to maturity hydroponically with nutrient solutions containing N as either all NO₃, all NH₄, or an equal mixture of both forms. At maturity, plants were harvested; separated into shoots, roots, and grain; and each part analyzed for dry matter and chemical composition. While the three cultivars varied in all parameters, mixed N plants always produced more tillers (by a range of 16 to 35%), accumulated more N (28 to 61%), phosphorus (P) (22 to 80%), and potassium (K) (11 to 89%) and produced more grain (33 to 60%) than those grown with either form alone. Although mixed N‐induced yield increases were mainly the result of an increase in grain bearing tillers, there was cultivar specific variation in individual yield components (i.e., tiller number, kernels per tiller, and kernel weight) which responded to N form. The presence of NH₄ (either alone or in the mixed N treatment), increased the concentration of reduced N in the shoots, roots, and grain of all cultivars. The effect of NH₄ in either treatment on the concentrations of P and K was variable and depended on the cultivar and plant part. In most cases, partitioning of dry matter, P, and K to the root decreased when NH₄ was present, while partitioning of N was relatively unaffected. Changes in partitioning between the shoot and grain were affected by N treatment, but varied according to cultivar. Based on these data, the changes in partitioning induced by NH₄ and the additional macronutrient accumulation with mixed N are at least partially responsible for mixed‐N‐induced increases in tillering and yield of winter wheat.     

Sorghum seedling root growth as influenced by H+, CA++, and MN++ concentrations 1

Root response mechanisms for acid soil tolerance adaptability are generally unknown. Sorghum [Sorghum bicolor (L.) Moench] cultivars (Funk G522DR, GP140, SC599, TAM428, SC283, and SC574) were grown in white quartz flintshot sand and watered with 0.01M sodium acetate buffer at pH 4.0, 4.5, 5.0, 5.5, or 6.0 and Ca⁺⁺ (0, 10, 100 mgl^‐1 as CaCl₂) or Mn⁺⁺ (0, 1.4, or 140.0 mgl^‐1 as HnCl₂). At the acid soil tolerance impact response phase (< 10 days old), Ca⁺⁺ did not influence initial root growth. Increased H⁺ concentration inhibited juvenile root growth equivalently in all six cultivars. This inhibition was reversed by exogenous GA₃ in Funks G522DR but not in SC283 or SC574. Excess Mn⁺⁺ (140 mgl^‐1) further decreased root growth. Induction of an auxinase inhibitor by GA₃ would support a hypothesis of H⁺ concentration influence on IAA transport and/or availability. Root growth matched IAA water partitioning and exogenous IAA (10^‐10 and 10^‐9 M) reversed the H⁺ concentration influence on root growth of SC283. We suggest that low pH (<4.8) soil influence on root growth is explicable as an influence on IAA synthesis and/or transport and that excess Mn⁺⁺, which is known to induce IAA oxidation, further exacerbates the deleterious growing conditions.     

Soil nitrogen fractions as influenced by sample preparation and extraction

Abstract

In order to evaluate the influence of extraction procedure on extractable nitrogen (N) fractions, fresh as well as dried soil samples were extracted with CaCl₂ at various temperatures (20,40,60, 80°C) for 30–120 minutes. Data obtained were compared with those from the electro‐ultra‐filtration (EUF) method. Increasing the drying temperature as well as the extraction temperature led to an increase in N_org content. The EUF and CaCl₂‐method produced comparable results for all N‐fractions (NO₃ ^‐, NH₄ ⁺, N_org) when an extraction temperature of 80°C was applied for two hours. Data presented suggested that the N_org fraction represented mainly the microbial biomass and may thus be considered as being easily available to plants.     

Properties of soil aggregates as influenced by tillage practices

Abstract. Changes in aggregate stability, density, and porosity as well as the water retention and nutrient contents of different aggregate size fractions due to intensive tillage were investigated. Three soils from Vicarello, Fagna and Gambassi in North Central Italy which had been under permanent vegetation, minimum or conventional tillage for more than seven years were studied. The aggregates on conventionally tilled plots were slightly denser and less porous than those on the untilled or minimum-tilled plots. The aggregates were less stable under conventional tillage on all soils. Conventional tillage reduced the proportion or macro-aggregates by 22% at Vicarello and 35% at Gambassi. There were no differences in macro-aggregate proportions between minimum- and conventionally tilled plots at Fagna. The potential of the dry aggregates to distintegrate upon contact with water was greatest in the conventionally tilled and least in the untilled treatments. The proportions of dry macro-aggregates (> 0.25 mm) in the untilled and tilled plots were 90 and 71%, respectively. The soil of the tilled plots contained less carbon and nitrogen than that of the untilled plots in all aggregate size fractions. The silt-plus-clay contents of the aggregates accounted for between 65 and 93% of variability in the water they retained at small potentials while organic carbon contents accounted for between 71 and 90% of variability in the stability of the aggregates irrespective of the tillage treatments.     

作物残茬翻埋对土壤性质的影响

Chemical transformation, nutrient release and changes in the energy content of decomposing rape, sunflower and soybean residues confined in buried fiberglass bags were assessed in a laboratory study during a 340-day incubation period. The organic C decreased by about 70% while total N, after initial decay, remained almost constant for each type of residue. The NH₄⁺-N was progressively oxidized and, consequently, the NO₃^--N increased. The C/N ratio narrowed with loss of C. Hemicellulose, cellulose and lignin decreased with different trends for each crop residue. The energy content, was reduced to about 25% in rape, 30% in sunflower and 20% in soybean residues. Total P, K, Ca and Mg contents decreased for each type of residue. The results suggest that the three residues could improve the nutrient pool of the soil.     

Soil porosity and water infiltration as influenced by tillage methods

The relations between soil pore structure induced by tillage and infiltration play an important role in flow characteristics of water and solutes in soil. In this study, we assessed the effect of long-term use of various tillage systems on pore size distribution, areal porosity, stained (flow-active) porosity and infiltration of silt loam Eutric Fluvisol. Tillage treatments were: (1) ploughing to the depth of 20 cm (conventional tillage (CT)); (2) ploughing to 20 cm every 6 years and to 5 cm in the remaining years (S/CT); (3) harrowing to 5 cm each year (S); (4) sowing to the uncultivated soil (no tillage (NT)), all in a micro-plot experiment. Equivalent pore size distribution was derived from the water retention curve, areal porosity – from resin-impregnated blocks (8 cm × 9 cm × 4 cm) and stained porosity – from horizontal sections (every 2 cm) of column samples (diameter: 21.5 cm, height: 20 cm) taken after infiltration of methylene blue solution. The pore size distribution curves indicated that the textural peaks of the pore throat radius of approximately 1 μm were mostly defined under NT, whereas those in the structural domain of radii of 110 μm radius—under CT. The differences among the tillage treatments were more pronounced at depth 0–10 cm than 10–20 cm. At both depths, the differences in pore size distribution between the tillage treatments were relatively greater in structural than those in the matrix domain. CT soil had the greatest areal porosity and stained porosity. The stained porosity as a function of depth could be well described by logarithmic equations in all treatments. Cumulative infiltration (steady state) as measured by the double ring infiltrometer method was the highest under CT (94.5 cm) and it was reduced by 62, 36 and 61% in S/CT, S and NT soil, respectively. Irrespective of tillage method, cumulative infiltration rates throughout 3 h most closely correlated with stained porosity in top layers (0–6 cm). Overall, the results indicate that soil pore system under CT with higher contribution of large flow-active pores compared to reduced and no tillage treatments enhanced infiltration and water storage capacity.     

Nitrate leaching as influenced by soil tillage and catch crop

Because of public and political concern for the quality of surface and ground water, leaching of nitrate is of special concern in many countries. To evaluate the effects of tillage and growth of a catch crop on nitrate leaching, two field trials were conducted in spring barley (Hordeum vulgare L.) under temperate coastal climate conditions. On a coarse sand (1987–1992), ploughing in autumn or in spring in combination with perennial ryegrass (Lolium perenne L.) as a catch crop was evaluated. Furthermore, rotovating and direct drilling were included. The experiment was conducted on a 19-year-old field trial with continuous production of spring barley. On a sandy loam (1988–1992), ploughing in autumn or in spring in combination with stubble cultivation and perennial ryegrass, in addition to minimum tillage, was evaluated in a newly established field trial. For calculation of nitrate leaching, soil water isolates from depths of 0.8 or 1.0 m were taken using ceramic cups. No significant effect of tillage was found on the coarse sand; however, a significant effect of tillage was found on the sandy loam, where leaching from autumn ploughed plots without stubble cultivation was 16 kg N ha⁻¹ year⁻¹ higher than leaching from spring ploughed plots. Leaching was significantly less when stubble cultivation in autumn was omitted. Leaching on both soil types was significantly reduced by the growth of a catch crop which was ploughed under in autumn or in spring. It was concluded that soil cultivation increased leaching on the sandy loam but not on the coarse sand, and that the growth of perennial ryegrass as a catch crop reduced leaching on both soil types, particularly when ryegrass was ploughed under in spring.