Composting municipal solid waste and biosolids and applying it on arable land have become an alternative way to treat waste in large municipalities in North America. However, cost of compost transportation and application constrains the compost use on the land further away from where it is produced. A fouryear experiment was conducted (1998)(1999)(2000)(2001) in less productive soils in Alberta to determine the effect of once in four year application of cocompost on soil nutrient dynamics and crop N uptakes. There were three crop blocks: barley (Hordeum vulgare L.), wheat (Triticum aestivum L), and canola (Brassica rapa), and they were rotated annually. The compost was only applied in 1998 at a rate of 50, 100 and 200 t/ha. Soil samples were taken in spring of every year after initial compost application to determine extractable N, P, K, S, Cu, Zn, Soil pH and EC. Each year, crops were harvested and N uptake was determined. Total concentrations of an array of heavy metals in the first year and fourth year after compost application were determined as well. The results showed that the release of N from the compost was high in the first year after compost application and then declined in each subsequent year. Similar to that release pattern was sulphur. The release of phosphorus from compost was steady throughout the four-year experimental time. Crop N uptake from compost application varied with crops and sites. The over all N use efficiency for three crops and two sites was 11%, 3%, 1% and 2% for the first and subsequent three years. The total heavy metal concentrations in the compost amended soils in the first and fourth year after compost application were similar, and they were below the standard of Canadian Fertilizer Act. Our results showed that N released from compost occurred mostly in the first two years after application, suggesting that an application frequency of once in every second year may be better than the once in every four year application strategy, especially with 100 t/ha application rate.

, J. 2003. Yield benefit of phosphorus fertilizer for wheat, barley and canola in Alberta. Can. J. Soil Sci. 83: 431-441. 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 soils (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. ). Les traitements consistaient en l'application de phosphate d'ammonium diacide avec la semence à raison de 0, de 6,5, de 13,1 et de 19,6 kg de P par hectare. La hausse moyenne du rendement grainier attribuable à l'usage d'engrais phosphatés s'établit à 10 % et ne varie guère d'une culture à l'autre. La hausse de rendement est significativement plus importante sur les sols gris (tchernozioms gris foncé, luvisols gris-gris foncé) que sur les sols noirs (tchernozioms noirs) ou bruns (tchernozioms bruns et brun foncé). La plus forte variation attribuable à l'engrais phosphaté relevée au moyen d'un des tests était de 27 % pour l'orge, de 15 % pour le blé et de 7 % pour le canola. La méthode de Kelowna et ses variantes donnent généralement la mesure la plus précise de la réaction aux engra...

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The movement and uptake of P in soils occur primarily in the soluble phase, so that the reliable simulation of P movement and uptake requires that the concentrations of soluble P forms be explicitly represented in mathematical models. To represent soluble P concentrations under dynamic boundary conditions, a convective‐dispersive model of P transport has been coupled to a model of P transformation in which adsorption‐desorption, precipitation‐dissolution, and ion pairing are explicitly represented as concurrent equilibrium reactions. This model is used to explain the temporal and spatial distribution of P among soluble and resin‐, NaHCO3‐, NaOH‐, and HCl‐extractable fractions in soils following amendment with KH2PO4. Simulated reductions in soil pH following different P amendments caused solid‐phase P in the model to be recovered more from resin‐ and NaOH‐extractable forms and less from HCl‐extractable forms as solution P concentration increased. These changes were consistent with those observed experimentally using a P fractionation procedure on a Malmo silt loam (Typic Cryoborall) following its equilibration with 0 to 512 mg L‐1 of KH2PO4 and following its irrigation for 205 d with 50 mg L‐1 of KH2PO4. Simulated displacement of cation coprecipitates from exchange sites allowed the model to reproduce the temporal and spatial patterns of water‐ and HCl‐extractable P in resin columns of different cation‐exchange capacities following a KH2PO4 surface amendment. The results of model testing suggest that changes in soluble P concentrations following P amendments may be represented from concurrent equilibrium reactions for adsorption‐desorption, precipitation‐dissolution, and ion pairing. However, the rate at which these reactions proceed remains uncertain.

Experiments were started in May 1998 at two sites to measure various crop responses to a mixed municipal solid waste-biosolids cocompost (named Nutri Plus) and examine the fate of certain metals associated with Nutri Plus compost. There were six treatments: Check, 50, 100, and 200 T compost/ha, NPKS (75 kg nitrogen (N) /ha, 20 kg phosphorus (P)/ha, 45 kg potassium (K) and 18 kg sulphur (S)/ha), PK (20 kg P, 45 kg K/ha), and three crops: canola (Brassica rapa cv. 'Hysyn 110'), wheat (Triticum aestivum L. cv. 'Roblin') and barley (Hordeum vulgare L. cv. 'Lacombe'). Each treatment was replicated four times and was in a complete randomized block design. In the compost treatments, 20 kg P and 45 kg K were applied due to low concentration of these two nutrients in the compost. Soil and plant samples were analyzed for nutrient content such as N, P and K. In addition, plant samples and soil samples after the compost application were also analyzed for elemental content of As, B, Cr, Co, Cu, Zn Se, Mo, Cd, Hg and Pb. The research results show that the compost slightly increased heavy metal concentrations in the soil but did not cause any phytoxicity to crops. Yield from 100 and 200 T/ha application was higher with the compost than with NPKS treatment. However, the yield of the 50 T/ha application was similar to that of NPKS treatment. Comparing the two sites, the compost apparently was more beneficial at Site 1 than at Site 2 in the year of application. This is likely due to the lower indigenous soil fertility and poor soil physical properties at Site 1. The N content in cereal grains was similar among the compost treatments but lower than the Check and NPKS treatments due to the diluting effect of higher yield. The oil content in canola seed was similar among all treatments. The results suggest that Nutri Plus compost applications generated positive yield responses in all three crops. Crop yield increased as the application rate increased. Heavy metal loading was not an immediate problem with the compost application, although it will limit total compost application over time to the same soil