K. S. Gill

Total and light fraction organic C in a thin Black Chernozemic grassland soil as affected by 27 annual applications of six rates of fertilizer N

Maintenance and sequestration of C is important to sustain and improve the quality and productivity of soils. The objective of this study was to determine the effects of 27 annual applications of six N rates (0, 56, 112, 168, 224 and 336 kg N ha−1 yr−1) on total organic C (TOC) and light fraction organic C (LFOC) in a thin Black Chernozemic loam soil. Nitrogen (ammonium nitrate) was surface-applied to bromegrass (Bromus inermis Leyss) managed as hay near Crossfield, Alberta, Canada. The concentration and mass of TOC and LFOC in the 0–5, 5–10, 10–15 and 15–30 cm soil layers increased with N rate and showed a quadratic response to N rate with significant R2 values, with their maximum values at 336 kg N ha−1 in the 0–5 cm layer and at 224 kg N ha−1 in other layers. But the increase in TOC and LFOC per kg of N addition was maximized at 56 kg N ha−1 and declined with further increase in N rate. These trends indicated that higher N rates would cause a faster build up of soil C, whereas lower N rates would achieve a greater increase in soil C per unit of N addition. Response of C mass to N application was much greater for LFOC (range of 697 to 156% increase) than for TOC (range of 67 to 17% increase). Percentage of LFOC in TOC mass increased with N rate. At the 168 to 336 kg N ha−1 rates, almost all of the increase in TOC in the surface 10 cm soil occurred as LFOC. Thus, LFOC was more responsive to N application and was a good indicator of N effect on soil C. The trend of change in soil TOC and LFOC was similar to hay yield and C removal in hay, which suggests that increasing hay yield with N application concurrently also increases soil organic C. In conclusion, long-term annual applications of N fertilizer to bromegrass resulted in a substantial increase in TOC and LFOC in the soil, thereby indicating that N fertilization can be used to sequester more atmospheric C in prairie grassland soils.

Distribution of acid extractable P and exchangeable K in a grassland soil as affected by long-term surface application of N, P and K fertilizers

Information on the fate and distribution of surface-applied fertilizer P and K in soil is needed in order to assess their availability to plants and potential for water contamination. Distribution of extractable P (in 0.03 M NH4F + 0.03 M H2SO4 solution) and exchangeable K (in neutral 1.0 M ammonium acetate solution) in the soil as a result of selected combinations of 30 years (1968–1997) of N fertilization (84–336 kg N ha−1), 10 years of P fertilization (0–132 kg P ha−1), and 14 years of K fertilization (0 and 46 kg K ha−1) was studied in a field experiment on a thin Black Chernozem loam under smooth bromegrass (Bromus inermis Leyss.) at Crossfield, Alberta, Canada. Soil samples were taken at regular intervals in October 1997 from 0–5, 5–10, 10–15, 15–30, 30–60, 60–90 and 90–120 cm layers. Soil pH decreased with N rate and this declined with soil depth. Increase in extractable P concentration in the soil reflected 10 years of P fertilization relative to no P fertilization, even though it had been terminated 20 years prior to soil sampling. The magnitude and depth of increase in extractable P paralleled N and P rates. The extractable P concentration in the 0–5 cm soil layer increased by 2.2, 20.7, 30.4 and 34.5 mg P kg−1 soil at 84, 168, 280 and 336 kg N ha−1, respectively. The increase in extractable P concentration in the 0–15 cm soil depth was 1.5 and 12.8 mg P kg−1 soil with application of 16 and 33 kg P ha−1 (N rate of 84 N ha−1 for both treatments), respectively; and it was 81.6 and 155.2 mg P kg−1 soil with application of 66 and 132 kg P ha−1 (N rate of 336 N ha−1 for both treatments), respectively. The increase in extractable P at high N rates was attributed to N-induced soil acidification. Most of the increase in extractable P occurred in the top 10-cm soil layer and almost none was noticed below 30 cm depth. Surface-applied K was able to prevent depletion of exchangeable K from the 0–90 cm soil, which occurred with increased bromegrass production from N fertilization in the absence of K application. As only a small increase of exchangeable K was observed in the 10–30 cm soil, 46 kg K ha−1 year−1 was considered necessary to achieve a balance between fertilization and bromegrass uptake for K. The potential for P contamination of surface water may be increased with the high N and P rates, as most of the increase in extractable P occurred near the soil surface.

Fertilizer N and P Effects on Root Mass of Bromegrass, Alfalfa and Barley

ABSTRACT Roots play a major role in maintaining organic matter in soil. Six field experiments were conducted to evaluate the effects of fertilizer N and P rates, application times and placement methods on root mass of meadow bromegrass (Bromus biebersteinii Roam and Shultz), smooth bromegrass (Bromus inermis Leyss), alfalfa (Medicago sativa Leyss) and barley (Hordeum vulgare L.) in the surface 15 cm of Black Chernozemic (Udic Boroll) and Gray Luvisolic (Boralf) soils in central Alberta, Canada. Root mass of grasses and barley was markedly increased with N and P fertilization and increase in root mass was greater with band placement than broadcast N. Black Chernozemic soils produced more root mass than Gray Luvisolic soils. Root mass of bromegrass and alfalfa was many times greater than that of barley. Root mass was greater for alfalfa than smooth bromegrass, and for bromegrass-alfalfa mixture than their pure stands. In conclusion, use of N and P fertilizers and growing of bromegrass, alfalfa and bromegrass grass-alfalfa mixture could be employed to increase root mass and possibly increase C storage in soil.

Light fraction organic N, ammonium, nitrate and total N in a thin Black Chernozemic soil under bromegrass after 27 annual applications of different N rates

Anadequate supply of N for a crop depends among others on the amounts of N thataremineralized from the soil organic matter plus the supply of ammonium andnitrateN already present in the soil. The objective of this study was to determine thebehaviour of light fraction organic N (LFN), NH4-N, NO3-Nand total N (TN) in soil in response to different rates of fertilizer Napplication. The 0–5, 5–10, 10–15 and 15–30cm layers of a thin Black Chernozemic soil under bromegrass(Bromus inermis Leyss) at Crossfield, Alberta, Canada,weresampled after 27 annual applications of ammonium nitrate at rates of 0, 56,112,168, 224 and 336 kg N ha−1. The concentration andmass of TN and LFN in the soil, and the proportion of LFN mass within the TNmass usually increased with N rates up to 224 kg Nha−1. The increase in TN mass and LFN mass per unit ofNadded was generally maximum at 56 kg N ha−1 anddeclined with further increases in the rate of N application. The percentchangein response to N application was much greater for the LFN mass than for the TNmass for all the N rates and all soil depths that were sampled. Mineral N intheform of NH4-N and NO3-N did not accumulate in the soil at≤ 112 kg N ha−1 rates, whereas theiraccumulation increased markedly with rates of ≥ 168 kg Nha−1. In conclusion, long-term annual fertilization at≤ 112 kg N ha−1 to bromegrass resulted insubstantial increase in the TN and LFN in soil, with no accumulation ofNH4-N and NO3-N down the depth. The implication of thesefindings is that grasslands for hay can be managed by appropriate Nfertilization rates to increase the level of organic N in soil.

Fertilizer Type, Tillage, and Application Time Effects on Recovery of Sulfate-S from Elemental Sulfur Fertilizers in Fallow Field Soils

Elemental sulfur (S) fertilizers may cost less per unit of S than sulfate-S (SO4-S) fertilizers, but oxidation of elemental S to plant-available SO4-S depends on fertilizer type and soil conditions. The objective of this study was to investigate the effects of S source, time of application, soil type and tillage on recovery of applied S as SO4-S in fallow field soils. Field experiments were conducted at five locations on Black Chernozem (Udic Boroll), Dark Gray Chernozem (Boralfic Boroll) and Gray Luvisol (Boralfs) soils in the Parkland zone of Canadian Prairies. The recovery of <100% from previous season Na2SO4 application in some cases indicated loss of fertilizer S from the soil SO4-S pool. The recovery results showed that only up to 44% of the spring applied elemental S could be recovered during the same growing season. The greater recovery of spring applied elemental S in October compared to July suggests that there is a considerable potential for SO4-S loss from soil over the winter and in early spring. The higher SO4-S recovery from Na2SO4 compared to elemental S fertilizers [Fine S, Urea S (A), Urea S (B) and Bentonitic S (A)] following their application in the previous season showed no extra residual benefit from elemental S fertilizers relative to the SO4-S fertilizer. Among the elemental S fertilizers, Fine S gave more recovery of SO4-S compared to Urea S (A), Urea S (B) and Bentonitic S (A). Tillage increased SO4-S recovery from applied S in one experiment but had inconsistent influence in another. The substantial differences in the SO4-S recovery from different soils indicated the influence of soil type on oxidation rate and recovery of applied S at a given time. In conclusion, the findings suggest that only a portion of the applied elemental S could be recovered as SO4-S at any of the sampling times. The recovery of residual S in the following year was always lower from elemental S fertilizers than Na2SO4, and the recovery at a given time was influenced by soil type and tillage.

Long-Term N Rates and Subsequent Lime Application Effects on Macroelements Concentration in Soil and in Bromegrass Hay

ABSTRACT Nitrogen fertilization is essential to produce high forage yields in the Canadian prairies but its long-term use have been observed to alter the chemical soil properties and composition of forage. Lime application is used to ameliorate soil acidity and create favorable soil conditions for sustainable crop production. We studied the effects of 27 annual applications (1968 to 1994) of 0, 56, 112, 168, 224 and 336 kg N ha−1 and one surface application of lime in 1991 (finely-ground CaCO3 to bring pH of surface 15 cm soil close to 7.0) at Crossfield, Alberta, Canada. We measured the concentration of macroelements in the 0–5, 5–10, 10–15 and 15–30 cm layers of a thin Black Chernozemic (Typic Boroll) soil and smooth bromegrass (Bromus inermis Leyss) hay in 1994. The concentration of NO3-N in soil increased linearly with N rate in all layers and it also increased with soil depth. The concentration of NH4-N increased markedly with N rate in the 0–5 and 5–10 cm layers, and its response to the N rate was linear for the 0–5 cm and quadratic for the deeper layers. The concentration of extractable P in the soil decreased at low N rates and then usually increased at higher N rates. The concentrations of extractable Ca, Mg, K and Na in the surface soil layers declined with increasing N rates in most cases, while their concentrations in deeper soil layers declined with higher N rates after initially increasing at lower N rates. The concentration of extractable Ca indicated that the downward movement of lime was restricted mainly to the 0–5 cm soil layer. Liming usually reduced the concentrations of NO3-N, P, NH4-N, Mg, K and Na in some of the shallow soil layers, but it tended to increase NO3-N, Mg and Na concentrations in some deeper soil layers and increased Ca concentration in shallow soil layers. In bromegrass hay, total N concentration increased and the concentrations of total P, S, Ca, Mg and K tended to decline with increasing N rates; and lime reduced the concentrations of total S, Mg, K and Na at some N rates and it did not affect total N, P and Ca concentrations. The increased NO3-N and NH4-N concentrations in the soil at high N rates may present an increased potential of N losses through runoff, leaching and denitrification. Liming induced reduction in NO3-N, NH4-N and P concentrations and increased soil pH in shallow soil layers, in combination with increased dry matter production of bromegrass indicated reduced potential of environmental pollution from N and P losses by runoff and denitrification as well as increased sustainability of bromegrass production.

Temperature, Soil Moisture, and Antecedent Sulfur Application Effects on Recovery of Elemental Sulfur as SO4‐S in Incubated Soils

Abstract The oxidation of elemental sulfur (S) to plant‐available SO4‐S is influenced by several factors. Experiments were conducted to compare the recovery of applied elemental S as SO4‐S in Dark Gray Chernozem (Boralfic Boroll), Black Chernozem (Udic Boroll), and Gray Luvisol (Boralfs) soils incubated at different temperature, moisture, and antecedent elemental S application conditions. For all soils and incubation periods, the recovery of SO4‐S increased with temperature from 6 to 36°C and with soil moisture from 40 to 90% field capacity (FC). At low temperature and soil moisture, the recovery of SO4‐S increased relatively steadily with incubation time up to 30 days, but at optimum temperature and soil moisture, the SO4‐S recovery was relatively faster at the start of the incubation and declined as incubation progressed. Previous addition of elemental S to soil accelerated the SO4‐S recovery. The rate of SO4‐S recovery was also influenced by soil type. The findings suggest that the amount of elemental S fertilizer needed to meet the crop requirements should be adjusted based on temperature, soil moisture, previous elemental S application history, and soil type.

Source, Application Method, and Cultivation Effects on Recovery of Elemental Sulfur as Sulfate‐S in Incubated Soils

Abstract Elemental sulfur (S) may have lower costs, but lack of its availability as plant‐available sulfate‐S (SO4‐S) at the time of crop uptake may render it ineffective as an S fertilizer. Four incubation experiments were conducted to investigate the comparative effects of particle size of elemental S and fertilizer products, application methods, and cultivation techniques on the recovery of elemental S as SO4‐S in four soils. Fertilizer products with fine elemental S particles (Flowable S, Fine S) or granules (crushed Bentonitic S) showed much higher recovery than those with large elemental S particles and granules (Urea S and Bentonitic S). Recovery of SO4‐S from different application methods followed a sequence of incorporation<broadcasting<banding<nesting. Cultivation generally increased recovery and the more thorough the cultivation, the greater the impact was. Immobilization of SO4‐S by microbes was not evident during first 6 wk of incubation, but it became evident in some soils and treatments after 6 wk of incubation period. Soils with high initial N and S concentrations showed more recovery. Overall, recovery was reduced by any factor that restricted mixing of elemental S particles into soil or reduced their exposed surface area for microbial action. Thus, appropriate fertilizer formulation as well as application and cultivation techniques to promote thorough mixing of elemental S particles into soil were critical to improve oxidation of elemental S to plant‐available SO4‐S.

Response of alfalfa hay yield to phosphorus fertilization in two soils in central alberta

Abstract Many soils in Alberta contain insufficient amount of available P and fertilizer P is needed for optimum crop yields. Fields experiments were conducted at two sites (Lacombe ‐ Black Chernozem silt loam and Botha ‐ Thin Black Chernozem loam) in central Alberta to determine the hay yield response of alfalfa (Medicago sativa leyss. cv. Rambler) to P fertilizer applied annually (0, 10, 20, 30, 40, and 60 kg P ha‐1) or once initially (60, 120, and 180 kg P ha‐1). In the initial application triple superphosphate was incorporated into soil prior to sowing of alfalfa in 1974 and in the annual application the P fertilizer was spread on soil surface for three years at Lacombe and for five years at Botha beginning in the spring of 1975. The hay yield increased with P application, but its magnitude of response to added P was lower at Botha than at Lacombe. The residual effect of large single P applications on hay yield lasted at least for five years.

Changes in extractable phosphorus between fall and spring in some alberta soils

Abstract In the Prairie Provinces of Canada, most soil samples for soil test P are taken in fall, although P fertilization and crop sowing normally occur in spring. Our objective was to compare soil test P values for samples taken in fall and spring. Extractable soil P (in 0.03 N NH4F‐0.03 N H2SO4) was measured in fall and spring samples at 49 sites in central Alberta and 4 sites in northern Alberta. Extractable P was less in fall‐ than ‐spring‐sampled soil at most sites. The average difference was 19.8 kg P/ha for the 49 sites in central Alberta and 34.9 kg P/ha for the 4 northern Alberta sites. In 27 of the 49 sites soil samples were taken in early fall, late fall and spring, with extractable P increasing by 21.9 kg P/ha from early fall to spring, but by only 1.1 kg P/ha from late fall to spring. The linear regression equation to predict the spring extractable P (Y) from early fall extractable P (X) was Y = 5.31 + 1.59X with an R2 value of 0.67 and from late fall extractable P (X) was Y = 6.67 + 0.89X w...