bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation of a simple model to describe carbon accumulation in a Brown Chernozem under varying fallow frequency
Authors: Campbell C A , Zentner R P , Selles F. , Liang B C , Blomert B.
Published: April 2011

Soil organic C (SOC) is readily influenced by crop management practices, such as summerfallowing. On the Canadian prairies, the area summerfallowed has decreased significantly in recent years. Our objectives were to determine the influence of fallow frequency on the rate of change in SOC in an Orthic Brown Chernozem, and to test the effectiveness of an empirical equation developed in an earlier study for estimating SOC changes in these rotations over 33-yr period. The rotations, which were initiated in 1967, all received adequate N and P fertilizers. They were (i) fallow-spring wheat (Triticum aestivum L.) (F-W), F-W-W, F-W-W-W-W-W and W-lentil (Lens culinaris L.) (W-Lent). Soil organic C was measured in the 0- to 15-cm and 15- to 30-cm depths in 1976, 1981, 1984, 1990, 1993, 1996 and 1999. No measurements of SOC were made in 1967; we estimated SOC starting values to be 30.5 Mg ha–1 in the 0- to 15-cm depth. In the period 1967 to 1990, when growing season precipitation was near normal for this semiarid region, SOC in the four rotations approached a steady state. However, a decade of much more favourable growing season precipitation in the 1990s increased C inputs, which resulted in a marked increase in SOC in the treatments. The empirical equation suggests, and the F-W and W-Lent rotations appear to confirm, that these rotations are approaching a new steady state at a higher level of SOC, reflecting the decade of favourable precipitation. Measured SOC levels were quite variable, emphasizing the difficulty of relying on measurements made over short time frames (e.g., 5-6 yr) when quantifying SOC changes. The equation effectively simulated the trends in SOC changes in all rotations, but consistently underestimated SOC levels in the W-Lent rotation by about 2 Mg ha–1. Estimates of difference in SOC between treatments were generally similar whether expressed on a mass/fixed depth or a mass/equivalent depth basis. Based on the estimates derived by the empirical equation, we estimated rates of SOC sequestration during the 1967-1990 period to be 0.03 Mg ha–1 yr–1 for F-W, 0.10 Mg ha–1 yr–1 for F-W-W, and 0.15 Mg ha–1 yr–1 for W-Lent. If we include the decade of more favourable precipitation (1967-1999), the rates were between 0.05 Mg ha–1 yr–1 for F-W and 0.20 Mg ha–1 yr–1 for W-Lent. These values are much higher than those estimated by others using the CENTURY model. We concluded that (i) simple models, such as that used in this study, are very useful for estimating management effects on SOC changes, and (ii) we must be cautious in extrapolating C sequestration estimates based on data from short-term experiments because future weather conditions are not easily predicted and weather can have an important impact on C sequestration. Key words: C sequestration, cropping frequency, crop rotations, wheat, lentil, flax, oats
A comparison of soil fertility and leaf nutrient status of sugar maples (Acer saccharum) in relation to microrelief in two maple forests in Québec
Authors: Roy G. , Sauvesty A. , Pagé F. , van Hulst R. , Ansseau C.
Published: April 2011

This study was conducted to provide a better understanding of the relationship between foliar nutrient status, maple dieback and soil quality. Fieldwork was conducted in four maple stands, two of which were located in the Appalachians at Tingwick and two in the Laurentians at Duchesnay. All stands were characterised by a mound and depression microrelief. In one of the Tingwick maple stands (T1) the predominant soil type was found on mounds, and was well to moderately well-drained (Leeds and Woodbridge series). At the other site (T2), the predominant soil type was in depressions, and imperfectly to poorly drained (Sainte-Marie and Brompton series). At the first Duchesnay site (D1) the predominant soil type was found on mounds and was well to rapidly drained (Ste Agathe series). At the second Duchesnay site (D2), the predominant soil type was also found on mounds, but was well to moderately well-drained (Sergent series). On all sites, the soils were acidic and nutrient poor. The lowest pH values and nutrient concentrations (in the H-Ah horizons) were found in maple stands with well-drained soils (T1 and D1) (P < 0.05). On these sites, maple dieback was less than 10%. It was on the poorly to imperfectly drained soils at Tingwick (T2), as well as on the moderately drained soils at Duchesnay (D2), that we observed the lowest biological activity. Although these soils were the most nutrient rich, we observed foliar nutrient deficiencies, and maple dieback in excess of 25%. Our results suggest that maple dieback is the result of a poor physiological adaptation of sugar maple to poor drainage conditions in the areas studied. Key Words: Dieback, Acer saccharum, forest soils, biological activity index
Boron fractionation in some Saskatchewan soils
Authors: Raza M. , Mermut A R , Schoenau J J , Malhi S S
Published: April 2011

Knowledge of B fractions is essential for understanding its chemistry and potential contribution to plant uptake. Four different extraction methodologies to determine readily available B were compared, using a four-step sequential B fractionation procedure, to reveal the nature of soil B in nine selected soils from the Brown and Gray Luvisol zones with different textures and management histories. The four soil extraction techniques were: hot water (HW), 0.01M CaCl2, 1 M NH4-acetate and anion exchange membranes (AEM). The other four fractions, specifically adsorbed, oxide bound, organically bound, and residual B were determined sequentially on the same soil samples. On average, HW extracted more B than 0.01M CaCl2, 1 M NH4-acetate, and AEM. In almost every soil, readily soluble B represented only a small proportion of the total B content, regardless of the extraction method used. Most soil B existed in the residual or occluded form, which accounted for between 92 and 99%, with an average of 97%, of the total soil B. The concentration of organically bound B was higher than that of oxide bound B and specifically adsorbed B, irrespective of the readily soluble B extracting solution used. Cation exchange capacity (CEC) appeared to be an important characteristic to predict the B pools. No significant correlation was found between soil organic carbon content and the different B pools, except for hot water soluble (HWS) B. Correlation coefficients between the B pools and particle size distribution were poor and correlation between carbonates and B pools were insignificant. The findings suggest that in Saskatchewan soils, readily soluble B is only a small proportion of the total B, and the majority of B exists as residual or occluded form. Hot water soluble B appears to be a good method to estimate available B. We found this method rather simple, efficient, and consistent. Key words: Boron fractionation, exchangeable B, extractable B, organically bound B, soluble B
Bacteria in agricultural soils: Diversity, role and future perspectives
Authors: Topp E.
Published: April 2011

Bacteria in soil are very diverse, very numerous, and functionally important, and have historically been an important object of research by Canadian microbiologists. Only a small fraction of bacteria in soils are amenable to culturing in the laboratory, limiting the ability to study these organisms. Canadian scientists have contributed to the development and implementation of both nucleic acidbased and chemical biomarker-based methods now widely used for assessing soil microbial biodiversity without the need for isolation and cultivation. Pesticide degradation, and the cycling of nitrogen in soils are used here to illustrate the significance of bacterial biodiversity to soil functions relevant to human and environmental health, and crop production . There remains much to be discovered about the genetic and functional biodiversity of soil bacteria, and much to be gained from this knowledge. A number of recommendations are made for future research in soil bacteriology. Key words: Soil quality, bacteria, microbial biodiversity, pesticide biodegradation, nitrogen cycling.
Mycorrhizal fungi biodiversity in Canadian soils
Authors: Dalpé Y.
Published: April 2011

The term "mycorrhiza" refers to the mutualistic symbiosis between fungi and the roots of a vast majority of vascular plants, distributed over almost any ecosystem. The fungal symbionts, primarily recognized for their beneficial impact on plant growth and plant protection, are integral components of soil ecosystems and as such, play an active role in improving plant productivity and diversity, soil microflora and microfauna diversity, and soil quality. Classified among major groups of true fungi, the study of their biodiversity and distribution has been explored for only a few decades. Major emphasis was first put on the mycorrhizal status of plants, on the evaluation of their benefits to plant growth, on their geographic distribution and soil inventories, and more recently on their relationship to plant diversity and productivity. In the 1950s, Canadian scientists were among world pioneers in the field of mycorrhizae research and they continue to be recognized by the international scientific community. Studies dealing with soil biodiversity of mycorrhizal fungi, including arbuscular, ecto-, ectendo-, ericoid- and orchid mycorrhizae, performed by Canadian researchers are presented here together with strategies and perspectives for a better exploitation of mycorrhizal fungal diversity in ecosystems. Key words: Symbiosis, mycorrhizae, arbuscular mycorrhizal fungi, ectomycorrhizal fungi, biodiversity, plant protection
Dissipation of part per trillion concentrations of estrogenic hormones from agricultural soils
Authors: Colucci Michael S , Topp Edward
Published: April 2011

Estrogenic hormones can affect fish at extremely low aquatic concentrations. A study was therefore undertaken to determine if agricultural soils, which can receive steroidal estrogenic hormones via livestock, poultry or municipal biosolids, could dissipate ng kg-1 soil concentrations of 17ß -estradiol or 17α-ethynylestradiol. Incubations with [4-14C]-17ß-estradiol, [6,7-3H(N)]-17ß-estradiol and [6,7-3H(N)]-17α-ethynylestradiol revealed that the major pathway of hormone dissipation was formation of soil-bound, non-extractable residues. The dissipation kinetics and pathways of both these compounds at these very low concentrations were entirely consistent with those previously observed at 1000-fold higher concentrations. We conclude that, in the absence of preferential or surface flow, very low concentrations of hormones can be expected to be dissipated, and the risk of contamination of water adjacent to agricultural soils treated with estrogen-containing biosolids during a temperate growing season is likely to be low. Key words: Endocrine disrupting chemical, soil, 17β-estradiol, 17α-ethynylestradiol, biodegradation
Impact of climate change scenarios on the agroclimate of the Canadian prairies
Authors: McGinn S. M. , Shepherd A.
Published: April 2011

Regional climate change scenarios for the Canadian prairies were generated using historic weather data and daily data from two Canadian Climate Centre general circulation models (GCM). Model CGCM1-A was a recent version release while its predecessor was model GCMII. The GCM data were combined with historic values to generate two additional scenarios. All scenarios were used to drive the modified Versatile Soil Moisture Budget model that assessed soil moisture, aridity and other agroclimatic indices. The modelled results for all scenarios were compared to those using the historic climate data. The model predicted earlier seeding dates for spring wheat between 18 and 26 d. Early seeding and harvest was shown to be an appropriate adaptive strategy that avoided more arid conditions in the late summer. The soil water deficit was lower under GCMII than historic values by 46 mm. For CGCM1-A, the soil water deficit was decreased by 8 mm across the Prairie Provinces compared to historic values. GCM scenarios predicted unchanged or increased soil water in the top 120 cm soil across the Canadian prairies compared to the historic scenario. There were some regions such as south eastern Saskatchewan and southern Manitoba where reductions in summer rainfall (for CGCM1-A) were large. These regions experienced the greatest benefit of earlier seeding dates. Key words: Climate change, agriculture, aridity, growing degree-days, soil moisture, seeding date, harvest date
Prediction of phosphorus concentration in tile-drainage water from the Montreal Lowlands soils
Authors: Beauchemin S. , Simard R. R. , Bolinder M. A. , Nolin M. C. , Cluis D.
Published: April 2011

Subsurface drainage systems can be a significant pathway for P transfer from some soils to surface waters. The objective of the study was to determine P concentration in tile-drainage water and its relationship to P status in surface soils (A horizons) from an intensively cultivated area in the Montreal Lowlands. The profiles of 43 soil units were characterized for their P contents and pedogenic properties. Tile-drainage water P concentrations were monitored over a 3-y r period on a weekly basis on 10 soil units, and four times during each growing season for the other 33 units. The soil units were grouped into lower and higher P sorbing soils using multiple discriminant equations developed in an earlier related study. The A horizons of the lower P sorbing soils had an elevated P saturation degree [mean Mehlich(III) P/Al = 17%] associated with total P concentrations in tile-drainage water consistently greater than the surface water quality standard of 0.03 mg total P L-1. Conversely, low P concentrations in tile-drainage waters (< 0.03 mg L-1) and a moderate mean Mehlich(III) P/Al ratio of 8% were observed in the higher P sorbing soil group. Total P concentrations in drainage systems were significantly related to soil P status in surface soils. Grouping soils according to their P sorption capacities increased the power of prediction based on only one soil variable. However, accurate predictions in terms of drain P concentration can hardly be obtained unless large dataset and other factors related to field management practices and hydrology of the sites are also considered. Therefore, a better alternative to predict the risk of P leaching is to work in terms of risk classes and rely on a multiple factor index. Key words: Tile-drainage water, phosphorus, P transfer, P loss, degree of soil P saturation, phosphorus index
13C CP/MAS-NMR spectra of organic matter as influenced by vegetation, climate, and soil characteristics in soils from Murcia, Spain
Authors: Faz Cano A. , Mermut A R , Ortiz R. , Benke M B , Chatson B.
Published: April 2011

Soils in southern Spain are low in organic matter (OM) and nutrients. Understanding the nature and dynamics of OM has potential to improve soil management technologies for sustainable crop production. The objective of this work was to establish the distribution of functional groups in organic-C from these soils using 13C CP/MAS-NMR spectroscopy and to investigate the influence of vegetation, climatic conditions, soil parameters, parent material, and soil order on these functional groups. No statistically significant variability in the distribution of organic-C groups was found as a result of the influence of either soil order or parent material. The content of O-alkyl-C in the soils under the Rhamno-Quercetum plant community was higher (95% probability) than in the soils under the Paronychio-Sideritidetum plant community. Soils located in the mesomediterranean climatic zone displayed a higher content of O-alkyl-C and a lower content of aromatic-C compared to the soils located in the thermomediterranean zone. These differences were statistically significant at 95% of probability. Vegetation and climatic conditions appear to play a major role in the OM decomposition processes in this region. Statistically significant and positive correlations were found between alkyl-C and both cation exchange capacity (CEC) and clay content indicating the recalcitrant nature of these organic compounds. Key words: Organic matter composition, Spanish soils, 13C CP/MAS-NMR spectra, Mediterranean soils, Alfisols, Mollisols, Aridisols
Surface application of mulches and biosolids affect orchard soil properties after 7 years
Authors: Neilsen G. H. , Hogue E. J. , Forge T. , Neilsen D.
Published: April 2011

Changes in selected soil chemical and physical properties of a coarse-textured orchard soil were measured 7 yr after establishing different orchard soil management strategies which were deemed to be environmentally sound in a high-density apple orchard. Several locally available mulches and organic wastes applied to the soil surface were maintained and assessed as to their effect on tree performance and soil properties relative to a standard commercial practice involving maintenance of a weed-free herbicide strip (known as the “check” practice). The soil chemical status of these sandy soils was readily altered when large amounts of nutrients were contained in applied mulches and biosolids. Thus, elevated soil C [and cation exchange capacity (CEC)], N, P, Zn, Fe, Mn and Cu occurred after cumulative application of 90 t ha-1 of biosolids; soil pH and Ca content increased beneath a high-Ca shredded paper mulch, and soil was enriched in P and K beneath a high-PK alfalfa mulch. Small but statistically significant decreases in soil bulk density, and increases in wet aggregate stability and infiltration rate were measured for some non-check soil management treatments. Of most practical importance among the physical property changes was increased surface soil moisture retention capacity associated with shredded paper mulches applied over biosolids. Cumulative yield and long-term vigour exceeded control trees for all soil management treatments and were best for treatments that included application of a shredded paper mulch. Few measured soil properties were correlated with long-term tree performance except for several soil pH-related parameters. However, surface application of mulches and biosolids generally improved soil nutrient status and physical properties while maintaining or improving crop yield. Key words: Biosolids, Malus domestica Borkh., mulches, soil fertility, water retention capacity
Sulphur fertilizer and tillage effects on early season sulphur availability and N:S ratio in canola in western Canada
Authors: Grant C. A. , Johnston A. M. , Clayton G. W.
Published: April 2011

Field studies in Manitoba, Saskatchewan and Alberta over 3 yr evaluated immediate and residual effects of source, timing and placement of S fertilizers on sulphate-S supply to canola (Brassica napus L.). The treatments were compared under conventional tillage (CT) and in the establishment years of a reduced (RT) system. Sulphate-S in the soil was measured for two weeks after seeding, using PRSTM-probes. Sulphur concentration and N:S ratio were measured in canola tissue at flowering. Tillage system had little effect on available sulphate, tissue S concentration, N:S ratio or response to S fertilization.

Ammonium sulphate (AS) generally increased tissue S concentration and reduced N:S ratio with all placements, and the effects of surface-applied ammonium thiosulphate (ATS) were similar to the effects of AS. Tiger 90, a bentonite-elemental S formulation, generally produced lower S concentrations in canola tissue at flowering than did AS, and levels were similar with elemental S and Tiger 90. Both tissue S concentration and N:S ratio were good indicators of S sufficiency for canola. Sulphate carryover from AS increased tissue S concentration and decreased N:S ratio in the year following application. In contrast, increases in tissue S concentration and decreases in N:S ratio were lower with Tiger 90 than AS. The oxidation of the residual elemental S in Tiger 90 could not be relied upon to increase tissue S concentration above deficiency levels in the year following application where soil sulphate levels were low. Key words: Elemental S, bentonite S, zero tillage, N:S ratio, PRS-probes
Impact of cattle grazing on prostigmatid mite densities in grassland soils of southern interior British Columbia
Authors: Battigelli J. P. , McIntyre G. S. , Broersma K. , Krzic M.
Published: April 2011

Soil mesofauna are an important part of soil ecosystems, but little is known about them in grassland ecosystems of southern interior British Columbia. In this s tudy, 12 300 organisms were examined and prostigmatid mites were most abundant, representing 95% of the total collection. Cattle grazing, sample depth and season of sampling influenced prostigmatid mite densities. However, grazing was the most significant factor, explaining 29% of the variation in prostigmatid mite density. Key words: Soil fauna, mesofauna, Prostigmata, Acari, range management
Soil inorganic nitrogen content in commercial potato fields in New Brunswick
Authors: Zebarth B. J. , Leclerc Y. , Moreau G. , Gareau R. , Milburn P. H.
Published: April 2011

Information on inorganic N content in commercial potato fields in Atlantic Canada is limited. Soil inorganic N measurements were collected from 228 commercial potato fields from 1999 to 2001. Soil NO3 content to 30 cm depth at planting ranged from 2 to 124 kg N ha-1, and was generally higher for preceding potato, red clover, or hay crops compared to preceding cereal or other crops. Soil NH4 content to 30 cm depth measured at planting ranged from 3 to 64 kg N ha-1, indicating that both soil NO3 and NH4 need to be measured to assess plant-available soil N content in spring. Soil NO3 content to 30-cm depth at tuber harvest ranged from 3 to 250 kg N ha-1, generally increased with increasing fertilizer N application rate, and differed among different potato cultivars. Soil NO3 content measured to 30-cm depth in spring ranged from 3 to 100% of soil NO3 at harvest in the preceding fall, indicating that highly variable losses of soil NO3 from the root zone occur between growing seasons. Key words: Nitrate, ammonium, Solanum tuberosum L.
Yield benefit of phosphorus fertilizer for wheat, barley and canola in Alberta
Authors: McKenzie R. H. , Bremer E. , Kryzanowski L. , Middleton A. B. , Solberg E. D. , Heaney D. , Coy G. , Harapiak J.
Published: April 2011

Crop responsiveness to P fertilizers on the Canadian Prairies has likely declined during the past three to four decades due to regular application of P fertilizer and reduced tillage. Its relationship to extractable soil P as determined by various soil tests may also have changed. The objective of this study was to evaluate five soil test P methods for three major crops across a wide range of soil types and environmental conditions. Small-plot P fertilizer trials were conducted at 154 locations across Alberta from 1991 through 1993. At each location, fertilizer responses were determined for one, two, or three crops: barley (Hordeum vulgare L.), spring wheat (Triticum aestivum L.) or canola (Brassica napus L.). Fertilizer treatments consisted of seed-placed monoammonium phosphate at rates of 0, 6.5, 13.1 and 19.6 kg P ha-1. The average increase in seed yield due to application of P fertilizer was 10%, with little difference among crop types. Relative yield increases were significantly greater in Gray soils (Dark Gray Chernozemics, Dark Gray-Gray Luvisols) than in Black (Black Chernozemics) or Brown soi ls (Brown and Dark Brown Chernozemics). The maximum variation in P fertilizer response accounted for by any soil test P was 27% for barley, 15% for wheat and 7% for canola. The Kelowna method and its derivatives generally provided the best fit with P fertilizer response. Only a modest increase in the proportion of variation that could be accounted for by soil test was achieved by multiple regressions with soil pH, clay or organic matter or by separate analyses of different soil types or years. The probability of a profitable yield response due to P fertilizer application did decline with increasing soil test P. However, profitable yield responses were frequent at all levels of soil test P for the first increment of 6.5 kg P ha-1 and low at all levels of soil test P for the third increment of 6.5 kg P ha-1 (19.6 kg P ha-1). The poor relationship of soil test P to fertilizer response was attributed to frequent but variable starter effects of P fertilizer and the infrequent occurrence of highly responsive sites. Key words: Soil testing, Olsen, Bray, Kelowna, fertilizer response functions, Hordeum vulgare, Triticum aestivum, Brassica napus
Effects of selected amendments on soil properties and emergence of wheat seedlings
Authors: Seker C.
Published: April 2011

Crusting can have a prominent effect on seedling emergence. Crust formation at the soil surface is a common feature of many soils including the silty loam soil (Aquic Haplocalsids) from the Konya plain examined in this investigation. The effects of different soil amendments on modulus of rupture and aggregate stability in water were measured in a pot experiment in the laboratory. Seedling emergence of wheat (Triticum durum Desf.) and penetration resistance was investigated in a microplot experiment in the greenhouse. Portland cement, barnyard manure (dairy cattle), city waste compost (municipal refuse) and wheat straw were used in the pot experiment, and Portland cement and barnyard manure were investigated in the microplot experiment. Soil amendments were added to the soil samples at rates of 0, 2, 4 and 6% (wt/wt) and the samples including a control were incubated at about field capacity water content for up to 100 d in the laboratory. The moduli of rupture values and water stable aggregates were measured after 25, 50, 75 and 100 d of incubation. All the soil amendments reduced the modulus of rupture compared with the control soil sample. The modulus of rupture of the control and mixes with Portland cement, barnyard manure, city waste compost and wheat straw (6%, wt/wt) after 100 d of incubation were 726, 0, 494, 564 and 113 kPa, respectively. Aggregate stabilities of the control and the soil amended with Portland cement, barnyard manure, city waste compost and wheat straw (6%, wt/wt) after 100 d of incubation were 5.16, 55.02, 10.82, 8.44 and 34.98%, respectively. Seedling emergences of wheat and penetration resistances of the control and the soil amended with Portland cement and barnyard manure (6%, wt/wt) in the microplots were 29, 80 and 36%; 489, 0 and 471 kPa, respectively. Key words: Surface sealing, aggregate stability, seedling emergence, penetration resistance.
Phosphorus removal from aqueous solutions by sorption on two volcanic soils
Authors: Zeng L. , Johnson R. L. , Li X. , Liu J.
Published: April 2011

The use of low-cost materials for P removal is of interest for developing cost-effective techniques for preventing P pollution. This paper reports a study on phosphate removal from aqueous solutions by sorption on two volcanic soils. The raw and HCl-treated soils were characterized with respect to oxalate-extractable and dithionite-extractable Al and Fe contents, surface area, and P sorption capacities. The phosphate sorption isotherms, kinetics, pH effects, and desorbability were evaluated in batch tests. The measured isotherm data were well fitted by the Freundlich and Temkin models. Phosphate sorption on these soils was relatively fast and the kinetics could be satisfactorily described by the simple Elovich and power function equations. The two soils had maximum phosphate sorption capacities of approximately 0.85 and 1.35 mg g-1 gram of soil at pH 6.0–6.5. The pH had different effects on phosphate sorption on these soils, likely due to either calcium phosphate precipitation or surface repulsion of the negatively charged phosphate species at a higher pH. Column flow-through tests using both synthetic phosphate solution and liquid swine manure confirmed the phosphate removal ability of the volcanic soils. It was concluded that volcanic soils could be potential low-cost materials for controlling P pollution from agricultural sources. Key words: Phosphate removal, volcanic soil, sorption, isotherm, kinetics, desorption
An analysis of litter nitrogen dynamics using artificial soils across a gradient of forest soil disturbances
Authors: Kranabetter J. M. , Chapman B. K.
Published: April 2011

The release of nutrients from a standard litter is often assumed to be solely a function of its decomposition rate. We tested whether nitrogen release would also be influenced by soil attributes affected by disturbance, such as interactions with soil microflora. Changes in nitrogen contents of decaying litter (Populus balsamifera) were compared across soil compaction and organic matter removal treatments in central British Columbia, using artificial materials to isolate litter bags from contact with forest floors or mineral soil. After 30 mo, nitrogen content of litter was only slightly higher on artificial soils than actual soils, suggesting that most nitrogen had been lost by leaching. A significant interaction, however, was detected in leaf nitrogen content between organic matter removal and soil compaction treatments that was not found on the artificial soils. This difference in nitrogen release led to a range in C:N ratios of 28 to 32 (from an initial C:N ratio of 52) for leaves at 1.5 g (70% mass loss). The differences in nitrogen release were relatively small and will perhaps be less important than other effects of soil disturbance (such as changes in litter quality) on nitrogen cycling. Key words: Nitrogen, decomposition, litter bag, translocation, compaction, forest floors
Agricultural intensification and the impacts on soil fertility in the Middle Mountains of Nepal
Authors: Westarp Stefanie von , Sandra Brown Hans Schreier, , Shah P. B.
Published: April 2011

Agricultural intensification in the Nepalese Middle Mountains has caused concern that soil inputs are insufficient to meet the higher nutrient demands of increased crop rotations, that increased chemical fertilizer dependency will cause soil acidification, and that soil fertility will decline. To examine changes in soil fertility dynamics over time and between land-use groups soil samples, farm surveys, and nutrient budgets were determined for less intensive irrigated and rainfed sites in 1994 and for intensive irrigated and rainfed sites in 2000 in the Jhikhu Khola watershed. Changes in fertilizer policy and in cropping rotation (introduction of potatoes and tomatoes and a decline in the use of a pre-monsoon fallow) have contributed to unbalanced and inadequate soil nutrition. Farmers in 2000 used significantly more compost and fertilizer (particularly diammonium phosphate) than in 1994. In irrigated sites, a significant increase in available soil P, a significant decline in exchangeable soil K, and a decline in base cation content was observed in sites sampled in 2000 versus 1994. Farmers intensively cultivating irrigated land need to address exchangeable soil K deficits, while reducing excess P inputs and taking measures to reduce the potential for soil acidification. In contrast, intensive rainfed sites have large surpluses in N, P, and K budgets for sites sampled in 2000, with significant increases in soil K, base saturation, and available soil P between 1994 and 2000. Given current crop yields, soil inputs to rainfed sites could be reduced to minimize unnecessary economic expenditures and eutrophication problems without depleting the soil nutrient pool. Key words: Agricultural intensification, soil fertility, phosphorus, potassium
Influence of compost on the physical properties and organic matter fractions of a fine sandy loam throughout the cycle of a potato rotation
Authors: Carter M. R. , Sanderson J. B. , MacLeod J. A.
Published: April 2011

Potato (Solanum tuberosum L.) rotations often require organic amendments to maintain or improve soil organic matter levels and soil physical properties. However, beneficial effects of compost can be modified by time of application and rotating tillage depth and intensity. This study was conducted to evaluate the effect of compost applied once at different phases in a 3-yr potato, barley (Hordeum vulgare L.), and red clover (Trifolium pretense L.) rotation on a range of soil physical properties and organic matter fractions for a Charlottetown fine sandy loam (Orthic Humo-Ferric Podzol) in Prince Edward Island. Soil samples (0–8 cm) were obtained during the second cycle of the rotation (after two compost applications) in the fifth year of the experiment. Soil properties were influenced by compost addition, time of compost addition, and crop phase. Compost-induced benefits in soil physical properties (bulk density, macro-porosity, oxygen diffusion rate, shear vane strength, water-filled pore space) were mainly expressed in the red clover phase of the rotation, where soil density was relatively high compared to the barley and potato phases, due to the absence of tillage. The soil physical parameters, however, were mainly within their established optimum ranges for this soil type. Soil water content at −0.033 MPa was increased by compost in the potato phase, compared to the control. Soil organic matter was influenced by both compost and crop C inputs. Compost increased soil particulate organic matter (POM) in the potato and barley phases. Due to differences in crop residue inputs, compost-related differences in organic matter were minimized in the red clover phase of the rotation. Compost addition increased potato tuber yield above the maximum yield obtained with nitrogen application. This “non-nitrogen” compost yield effect may be related to the slight, but significant, improvement in soil water-holding capacity. Overall , compost application in an intensive 3-yr potato rotation provided benefits for potato productivity and in both soil physical and biological properties. Key words: Soil organic carbon, particulate organic matter, soil physical properties, compost amendment, potato yield, eastern Canada
Phosphorus diffusion from monocalcium phosphate co-applied with salts in a calcareous soil
Authors: Kumaragamage D. , Akinremi O. O. , Cho C. M. , Goh T. B.
Published: April 2011

Mixing non-phosphatic salts with fertilizer P influences the solubility and mobility of P in soils. Little evidence, however, is available regarding the mechanisms causing such effects. The object ives of this study were to investigate the effects of mixing fertilizer P with (NH4)2SO4, MgSO4 or (NH2)2CO on the diffusion of P in a calcareous soil (Gleyed Rego Black Chernozem), and to identify the causes for such effects. To the surface of 50-mm-long soil columns, maintained at field capacity water content, 32P-labelled monocalcium phosphate (MCP) was applied alone or in combination with (NH4)2SO4, MgSO4 or (NH2)2CO. Ratios of applied P:N, P:Mg and P:S were 1:5, 1:4.5 and 1:6, respectively. Extraction and analysis of each 2-mm layer of the columns after incubation for 1, 2, 3, and 4 wk revealed that the addition of (NH4)2SO4 and MgSO4 with MCP significantly increased P diffusion whereas (NH2)2CO had little or no effect. The mechanisms of such effects were identified using a multi-ionic, mechanistic, diffusion model. According to model predictions, the dissolution of MCP was increased by more than twofold when mixed with (NH4)2SO4 and MgSO4, and by 1.2-fold when mixed with urea. The main difference between SO4 salts and urea in affecting P diffusion was the competition between the anion of the salt and P for precipitation with Ca. Sulphate competed strongly with P, reducing the precipitation of Ca phosphates. Application of urea increased soil pH initially, but eventually soil pH decreased with nitrification of NH4. Initial increase in pH to above 8.0 favoured precipitation of Ca phosphate, but the pH was not high enough to favour CaCO3 precipitation. The application of P fertilizers with fertilizers containing SO4 could be beneficial in calcareous soils due to enhancement of P solubility and mobility. Key words: Calcareous soils, phosphorus diffusion, precipitation, sulphate salts, transport model, urea
Gas diffusion and air-filled porosity: Effect of some oversize fragments in growing media
Authors: Caron Jean , Rivière Louis-Marie , Guillemain Gilles
Published: April 2011

Large particles are often added to growing media to improve air-filled porosity, an often-reported growth-limiting factor. Previous studies have shown that large fragments can leave air-filled porosity unchanged and actually decrease the air exchange characteristics in peat:bark and pure peat media, with an adverse effect on plant growth. Thirteen different growing mixes composed of perlite, bark, peat, sand, rockwool, wood and coco fibre, in which the size of the larger fractions was varied, were tested. Air-filled porosity, easily available water, pore effectiveness coefficient, and diffusivity were examined in these mixes. Air-filled porosity was found to be the highest in mixes where the largest fraction was composed of coarser particles. Pore effectiveness coefficient was found to decrease with the increasing coarseness of the largest fractions. Gas diffusivity was found to be highest when intermediate (2–4 mm) fragments were used as the largest fraction of the mixes. These findings applied to impermeable, disk- or spherically shaped, coarse fragments (perlite, coco hulls, bark), but did not apply to threadlike coarse material (wood fibres). Gas diffusivity values (at a water potential of −0.75 kPa) obtained for rockwool, the peat:bark mix containing 2- to 4-mm bark particles, the peat:medium wood fibre mix, the peat:fine perlite (0.8–2 mm) mix and the pure fine coconut medium were not statistically different one from another. Air-filled porosity was negatively correlated to the fractions less than 1 mm, between 0 and 0.2 mm and between 0.2 and 0.8 mm. Easily available water, pore effectiveness coefficient and gas diffusivity were not correlated to particle size distribution, indicating that these properties cannot be estimated based on particle size and must instead be measured directly. Key words: Aetion, peat substrates, perlite, bark, available water
Impact of arbuscular mycorrhizal fungi on N and P cycling in the root zone
Authors: Hamel Chantal
Published: April 2011

The influence of arbuscular mycorrhizal fungi (AMF) on soil processes is difficult to define, in part because it varies with the plant and fungal geno types as well as with environmental conditions. The influence of AMF on N cycling is just being discovered. This short review examines areas of knowledge related to the nature of the mycorrhizosphere, AMF-microbe interactions, and N and P mobilization in the root zone. The role AMF could play in the root zone in N and P dynamics is presented. The spatial organization of roots and hyphae in soil suggests that AMF may enhance the reabsorption of nutrients lost through root exudation. These fungi influence soil microorganisms and, hence, they may influence biochemical reactions in soil including mineralization of organic matter and nitrification. AMF seem to improve the capacity of their host plant to use organic sources of P and N. AMF might improve the ability of plants to compete with saprotrophs for the uptake of P and N. The impact from this latter effect of AMF could exceed that stemming from their possible direct use of amino-acid-N, their production of phosphatase enzymes and possibly of organic anions. Better competitive ability of mycorrhizal plants under conditions of low soil P and N levels could reduce saprotrophic populations and, if this occurs, regulate soil organic matter turnover rate. The management of biological soil resources, in truly sustainable cropping systems, may be the largest challenge in crop production. Key words: Arbuscular mycorrhizal fungi, soil functioning, nitrogen cycling, phosphorus cycling, soil fertility, soil microbial community
Early growth and nutrient dynamics of planted Pinus banksiana seedlings after slash-pile burning on a boreal forest site
Authors: Thorpe H. C. , Timmer V. R.
Published: April 2011

Containerized jack pine (Pinus banksiana Lamb.) seedlings were planted in 10 paired slash-pile-burn and control plots established on a recent clearcut in north eastern Ontario to assess early impacts of intensive fire on soils and plant growth and nutrition. Root zone soil and seedlings were sampled one growing season after planting. The control seedlings exhibited modest growth without gain in N content, indicating reliance on internal nutrient reserves for growth on this low-fertility site. Slash-pile burning reduced seedling mortality, and markedly increased height, rootcollar diameter, and biomass growth, as well as uptake of N, P, K, Ca and Mg. The response was attributed to greatly improved soil fertility following fire, characterized by increased pH, extractable NO3- and NH4+ , available P, and exchangeable K, Ca and Mg. Significant correlations between corresponding soil tests and seedling nutrient composition indicated that laboratory extractions effectively reflected nutrient availability to plants. The highest correlations were associated with N. Vector diagnosis identified N as the most limiting nutrient constraining growth on the burns, even though base cation increases (mainly from ash) were relatively larger than extractable N in the soil. These early responses in soils and plants to intensive fire may have long-term effects on plantation development. Key words: Slash pile, prescribed fire, soil fertility, seedling nutrition
Soil compaction and water content as factors affecting the growth of lodgepole pine seedlings on sandy clay loam soil
Authors: Bulmer C. E. , Simpson D. G.
Published: April 2011

The response of lodgepole pine (Pinus contorta Dougl. var. latifolia Engelman.) seedlings to three levels of soil compaction and water content was evaluated in raised beds filled with a sandy clay loam soil. In compacted soils, seedling survival, height, root collar diameter and root growth were reduced. Soil water regime was adjusted with irrigation to levels associated with plant moisture stress (near wilting point) and limiting soil aeration (near 0.10 m3 m-3 air-filled porosity). Soil water regime affected seedling performance, with higher survival, root collar diameter and root growth observed on treatments with higher water content. Compaction had detrimental effects on growth at all levels of soil water availability. Compaction and water content had strong effects on soil mechanical resistance. Limitations to seedling growth and survival were at least partly explained through their relationships with soil water content and soil mechanical resistance, and combinations of these factors as described by the least limiting water range concept. Key words: Soil compaction; soil physical properties; water availability; plant growth response; least limiting water range
Assessing the temporal stability of spatial patterns in crop yields using combine yield monitor data
Authors: Lauzon John D , Fallow David J , O’Halloran Ivan P , Gregory Sharon D. L. , von Bertoldi A. Peter
Published: April 2011

Using previous years’ yield patterns may be one method of breaking a field into management zones for the purpose of site-specific management. For this method to be useful there must be temporal stability of yield patterns and there must be a sound method of assessing the spatial-temporal stability of yield in a field. To this end, a method was developed to give a non-biased estimate of the within-field spatial-temporal stability of yield. The method determined the probability that the normalized yield for all years available at a given location in the field fit within the accuracy limits of the combine. Combine accuracies of ± 2.5%, 5% and 10% of the field mean yield and gridded data of 3 m, 6 m, and 9 m cell sizes, as well as crop choice were all included in the model to assess its sensitivity to changes in these factors. The resulting spatial-temporal stability maps were well correlated with visual estimations of the spatial yield patterns. The model results were highly influenced by the inputted combine accuracy, but grid size and crop choice had little affect on the proportion of the field or the spatial pattern of temporal stability in the two field sites examined. The sensitivity of the model to changes in the input value for the combine accuracy indicated that a good estimate of this value is required for the determination of the stable patterns in a field. Key words: Spatial-temporal stability, yield
Environmental Mehlich-III soil phosphorus saturation indices for Quebec acid to near neutral mineral soils varying in texture and genesis
Authors: Pellerin Annie , Parent Léon-Étienne , Fortin Josée , Tremblay Catherine , Khiari Lotfi , Giroux Marcel
Published: April 2011

The Mehlich-III method (M-III) (Mehlich 1984) is a multinutrient agri-environmental routine soil-testing procedure used in many jurisdictions in North America, but one that is affected by soil texture. The PW determined by the Sissingh (1971) method is an index of surface water contamination and desorbed P that is not influenced by soil texture and that can be used to define specific M-III critical environmental indices by soil texture group. Our objective was to define critical environmental indices by relating (P/Al)M-III to PW. We analyzed 275 soil samples from surface, and 175 from subsurface layers, varying in genesis, texture, and pH. The relationship between PW and (P/Al)M-III was influenced by soil properties, particularly soil texture and genesis. Fine-textured (> 300 g clay kg-1) and gleyed soils tended to release more PW at a given (P/Al)M-III compared with coarse-textured (≤ 300 g clay kg-1) and podzolized soils. Using a critical value of 9.7 mg PW L-1 derived from the literature, critical environmental (P/Al)M-III ratios were found to be 0.131 for coarse-, and 0.076 for fine-textured soils. Subsurface PW increased significantly with (P/Al)M-III above 0.131 in the plough layer of coarse-textured soils, but was independent of (P/Al)M-III in fine-textured soils, indicating contrasting mechanisms of P accumulation in subsurface layers (matrix vs. preferential flow). After accounting for soil texture, (P/Al)M-III appeared to be a useful index of P accumulation in Quebec mineral soils. Key words: Soil phosphorus saturation, Mehlich-III soil extraction method, water-extractable phosphorus, soil environmental phosphorus threshold, soil texture