ALBERT

Description: An earlier study indicated that cereal straw may be removed after harvest without affecting crop production, soil organic matter and microbial biomass. Further measurements of early indicators of changes in soil organic matter, viz., the light fraction and mineralizable C and N, confirm that straw removal is superior to straw incorporation with moldboard ploughing, and comparable to straw incorporation by disking, in C and N retention and turnover. Key words: Carbon, light fraction, mineralization, nitrogen, straw management

Description: Pipeline construction on the Canadian boreal plain occurs on woodland and/or agricultural fields, but soil recovery from its impact is not well documented. Therefore, we quantified changes over 3 yr (1992 to 1994) in the chemical properties of two Grey soils and the physical properties of a Grey soil that were subjected to pipeline burial and cropped to barley. The pipeline right-of-way (RoW) was divided into three zones: a road (or work) area used for vehicular traffic, a trench area for burying pipeline, and a pile (or spoil) area where soil was stockpiled during excavation. Pipeline construction resulted in mixing of subsoil material with topsoil, and the chemical properties most affected were those that varied most with depth. The pH, electrical conductivity, soluble sulphate, and exchangeable Ca and Na were increased in the surface 20 cm of soil, particularly the road and trench areas. The affected properties moderated 2 or 3 yr after pipeline construction as soluble components were dissolved or dispersed and translocated back to lower soil depths. The RoW zones had increased soil strength and compaction, and reduced water retention and infiltration rates. However, the deterioration in soil physical condition was similar across the RoW zones, indicating that it was due mainly to land clearing, a requirement to convert woodland to agricultural land. Improvement in bulk density, and water infiltration and retention in 1993 and 1994 indicated that the RoW was undergoing rehabilitation with time as a result of natural processes and annual cropping. Key words: Chemical properties, exchangeable cations, sulphate, physical properties, soil-water, pipelines

Description: Environment and management effects on the N supply to crops are not well understood. We assessed the influence of tillage system (conventional tillage or no-till), N fertilizer (0 or 60 kg N ha-1) and year on N sources and supply of a Dark Brown Chernozem loam soil, and N utilization by spring wheat (Triticum aestivum L.) in 2 yr. The main N source was mineralized N; only 14–23% of wheat N was derived from fertilizer, and non-exchangeable ammonium made no measurable contribution. Soil NO3 and exchangeable NH4 content at sowing and net N mineralization during the growing season (Nmin) were influenced more by year than by N addition and tillage. Nmin was 90–100 kg N ha-1 in 1999, a moist growing season but only 21–39 kg N ha-1 in 2000, a drier year. In both years, soil inorganic N to 60 cm at sowing averaged about 60 kg N ha-1 of which half was N mineralized since the previous harvest. Year accounted for 65–81% of the variation in N uptake. Fertilization increased N uptake and wheat yields, especially in 2000, but fertilization and tillage had no effect on post-heading N uptake and N translocation. Nitrogen use efficiency (NUE) and N recovery were lower with N applied and not affected by tillage. Our study indicated that available N was affected more by environment than management. In dry conditions, when Nmin is low, N application may be more effective in increasing yield and N uptake than in wet years, an observation that may merit further attention. Key words: Available N, N mineralization, N recovery, N use efficiency, non-exchangeable ammonium, tillage

Description: The effects of tillage and crop rotations on soil N availability and economy were evaluated over two rotation cycles to address the paucity of such information. From 1993 through 2000, soil was sampled to 120 cm in the autumn from four crop rotations : (i) continuous wheat (Triticum aestivum L.), (ii) field pea (Pisum sativum L.)-wheat-canola (Brassica rapa L.)-wheat, (iii) red clover (Trifolium pratense L.) green manure-wheat-canola-wheat/red clover, (iv) fallow-wheat-canola-wheat, and analysed for KCl-extractable N. The rotations were managed under a conventional tillage (CT) or a no-till (NT) system, and were fertilized based on soil test results. A N budget was constructed for each cropping system comprising N added in seed and fertilizers, and by symbiotic fixation and N exported in the grain. More nitrate accumulated under CT than NT, resulting in lower N fertilizer application rates for CT plots. Soil mineralizable N was higher under NT than CT, and was not influenced by crop rotations. The trend for residual soil nitrate among crop rotations was: fallow rotation 〉 green manure rotation 〉 continuous wheat 〉 field pea rotation, due mostly to residual nitrate following the first phase of the rotations. There was no interaction of tillage with rotation. The continuous wheat and field pea rotation maintained a balanced N budget. The red clover rotation resulted in net N import in each rotation cycle of approximately 25 kg ha-1 under CT and 37 kg ha-1 under NT; net N export from the fallow rotation was 30 kg ha-1 under NT and 46 kg ha-1 under CT. Key words: Field pea, fallow, red clover, N economy, tillage, wheat

Description: Nutrient cycling is an important part of integrated nutrient management. The litterbag method was used in field experiments to determine potassium (K) release patterns from red clover (Trifolium pratense) green manure (GM), field pea (Pisum sativum), canola (Brassica rapa) and monoculture wheat (Triticum aestivum) residues under conventional and zero tillage from 1998 to 1999 and from 1999 to 2000. Potassium contained in crop residues ranged from 25 kg ha-1 in wheat to 121 kg ha-1 in pea residues, both under zero tillage. The percentage of K released over a 52-wk period ranged from 65% of pea K under zero tillage to 99% of clover K under conventional tillage, and the amounts released were 20–32 kg ha-1 from wheat, 31–52 kg ha-1 from canola, 28–79 kg ha-1 from pea, and 31–118 kg ha-1 from legume GM residues. In both trial periods, K from wheat residues was released at a faster rate under conventional tillage than under zero tillage during the first 10 wk of residue decomposition. In contrast, K from pea and canola residues was released more quickly under zero tillage than under conventional tillage. The effect of tillage on K release from GM residues was similar to that on pea and canola residues in 1998–1999, but similar to that on wheat residues in 1999–2000. Correlations between K release and residue quality were inconsistent, presumably because K is not a structural component of plant tissue, and therefore its release is probably related more to leaching than to residue decomposition. These results show that crop residues recycle substantial amounts of K for use by subsequent crops in rotation. Key words: Conservation tillage, crop residue quality, crop rotation, organic soil amendments

Description: Field experiments were conducted on Dark Gray Luvisolic soils (Typic Cryoboralf) from 2004 to 2006 (wheat-canola-barley rotation) near Star City, Saskatchewan, and from 2004 to 2007 (barley-canola-wheat-barley rotation) near Beaverlodge, Alberta. The aim was to compare the effects of controlled-release urea (CRU) vs. conventional urea (hereafter called urea) on seed yield and N (i.e., protein) concentration, and N use efficiency (NUE). The treatments were combinations of tillage system [conventional tillage (CT) and no tillage (NT)], and N source (urea, CRU and a blended mixture), placement method (spring-banded, fall-banded and split application) and application rate (0-90 kg N ha-1). There was no tillage × fertilizer treatment interaction on the measured crop variables. Seed yield and crop N uptake and, to a lesser degree, seed N concentration generally increased with N application to 90 kg N ha-1. Fall-banded CRU or urea generally produced lower crop yield and N uptake than spring-banded CRU or urea. Split application of urea (half each at seeding and tillering) resulted in higher seed yield and N concentration in at least 3 of 7 site-years than did CRU and urea applied at a similar rate. A blend of urea and CRU was as effective as spring-banded CRU (at Star City only). Seed yield, N recovery and NUE were higher with spring-banded CRU than urea in 2 site-years, and similar to urea in other site-years. We conclude that for boreal soils of the Canadian prairies, spring-banded CRU is as effective as urea, and in some years more effective, in increasing crop yield and N recovery; however, urea split application can be even more effective in addition to having an advantage in managing risk.Key words: Controlled-release urea, Gray Luvisol, nitrogen source, nitrogen recovery, nitrogen use efficiency, tillage systems

Description: Pipeline construction on the Grey soils of the Canadian boreal plains, which have a thin Ah horizon, could have considerable impact on their properties and productivity. This study was conducted because the effects of pipeline installation on crop yield and biological properties of these soils have not been well-documented. Soil was sampled from a Grey Luvisol and a Dark Grey Solod prior to pipeline construction in 1991, and in each of the following 3 yr. The right-of-way (RoW) was divided into three zones: a road (or work) area used for vehicular traffic; a trench where the pipeline was buried; and a pile (or spoil) area where soil was stockpiled during construction. The RoW was cropped to barley (Hordeum vulgare L.) in 1992 through 1994. Barley yield was low in 1992 (830–1120 kg ha−1), and near average (2050–3290 kg ha−1) in 1993 and 1994. Except for low shoot P concentration (1.1–1.3 mg g−1) in 1992, macronutrient concentrations (N, P and K) in barley tissues were within normal ranges. Soil organic carbon was reduced by 12–28% in all RoW areas in 1993 and 1994. Soil total N was reduced by 29–49% in all RoWs in 1992 and increased slightly from those levels in 1993 and 1994. Pipeline construction affected soil microbial biomass carbon (MBC) in the three RoW areas differently, and the effect was not consistent from year to year. However, the average level of MBC was not adversely impacted. In 1994, soil phosphatase activity in the RoW zones tended to be lower as compared to pre-pipeline installation, particularly in the pile area of the Dark Grey Solod. It is concluded that although some soil biological properties were degraded by pipeline construction, and barley yield was reduced in 1992, crop production in the following 2 yr was not significantly affected. Key words: Barley, carbon, microbial biomass, nitrogen, phosphatase, pipeline

Description: Molybdenum, Co and B concentrations in, and uptake by, corn and bromegrass were measured over a period of several years from three field experiments in which sewage sludge was applied and compared with ammonium nitrate as a source of N. There was little effect of sludge on B and Co concentrations in the crops grown. Slight increases in uptake were apparently due to yield increases due to sludge. A lime-treated sludge increased Mo concentration in plant tissues after several years of sludge application. The increase in plant Mo concentration was highest in the eighth and last year of the experiments, although lime-sludge application had ceased 1–3 yr previously. The soil-sludge interactions contributing to increased Mo uptake are discussed. Key words: Molybdenum, cobalt, boron, sewage sludge, corn (Zea mays L.), bromegrass (Bromus inermiss Leyss).

Description: A loamy soil amended with sewage sludges chemically treated with Ca(OH)2, Al2(SO4)3 or FeCl3 was used for P adsorption studies. Phosphate adsorption was increased by sludge application in the order: Ca-sludge 〉〉 Al-sludge = Fe-sludge 〉 untreated soil, and was associated wtih the increase in CaCO3 and hydrous iron and aluminum oxide countents resulting from sludge application.

Description: A field study was conducted to determine the effects and interactions of crop sequence, tillage and residue management on labile N pools and their availability because such information is sparse. Experimental treatments were no-till (NT) vs. conventional tillage (CT), and removal vs. retention of straw, imposed on a barley (Hordeum vulgare L.)-canola (Brassica rapa L.)-field pea (Pisum sativum L.) rotation. 15N-labelling was used to quantify N uptake from straw, below-ground N (BGN), and fertilizer N. Straw retention increased soil microbial biomass N (MBN) in 2 of 3 yr at the four-leaf growth stage of barley, consistent with observed decreases in extractable soil inorganic N at seeding. However, crop yield and N uptake at maturity were not different between straw treatments. No tillage increased soil MBN, crop yield and N uptake compared to CT, but had no effect on extractable soil inorganic N. The greater availability of N under NT was probably related to soil moisture conservation. Tillage effects on soil and plant N were mostly independent of straw treatment. Straw and tillage treatments did not influence the uptake of N from its various sources. However, barley following pea (legume/non-legume sequence) derived a greater proportion of its N from BGN (13 to 23% or 9 to 23 kg N ha-1) than canola following barley (nonlegumes) (6 to 16% or 3 to 9 kg N ha-1). Fertilizer N constituted 8 to 11% of barley N uptake and 23 to 32% of canola N uptake. Straw N contributed only 1 to 3% of plant N uptake. This study showed the dominant influence of tillage on N availability, and of the preceding crop or cropping sequence on N uptake partitioning among available N sources. Key words: Crop residue, crop sequence, labile nitrogen, nitrogen uptake, pea, tillage