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.
Permafrost thaw subjects previously frozen organic carbon (OC) to microbial decomposition, generating the greenhouse gases (GHG) carbon dioxide (CO2) and methane (CH4) and fueling a positive climate feedback. Over one quarter of permafrost OC is stored in deep, ice‐rich Pleistocene‐aged yedoma permafrost deposits. We used a combination of anaerobic incubations, microbial sequencing, and ultrahigh‐resolution mass spectrometry to show yedoma OC biolability increases with depth along a 12‐m yedoma profile. In incubations at 3 °C and 13 °C, GHG production per unit OC at 12‐ versus 1.3‐m depth was 4.6 and 20.5 times greater, respectively. Bacterial diversity decreased with depth and we detected methanogens at all our sampled depths, suggesting that in situ microbial communities are equipped to metabolize thawed OC into CH4. We concurrently observed an increase in the relative abundance of reduced, saturated OC compounds, which corresponded to high proportions of C mineralization and positively correlated with anaerobic GHG production potentials and higher proportions of OC being mineralized as CH4. Taking into account the higher global warming potential (GWP) of CH4 compared to CO2, thawed yedoma sediments in our study had 2 times higher GWP at 12‐ versus 9.0‐m depth at 3 °C and 15 times higher GWP at 13 °C. Considering that yedoma is vulnerable to processes that thaw deep OC, our findings imply that it is important to account for this increasing GHG production and GWP with depth to better understand the disproportionate impact of yedoma on the magnitude of the permafrost carbon feedback.
An experiment was conducted in subarctic Alaska from 1999 to 2001 to determine the effect of liquid and solid cattle (Bos taurus) manure application rates on smooth bromegrass (Bromus inermis Leyss.) and oat (Avena sativa L.) biomass production, nutrient uptake, and soil properties. One-time manure application of 100 and 200 kg N ha 21 was made in May 1999 in comparison with annual fertilizer application of 50, 100, and 200 kg N ha 21. In the first year, liquid manure at 100 and 200 kg N ha 21 generated 3036 and 4292 kg ha 21 smooth bromegrass biomass, respectively, statistically (p $ 0.05) similar to that of fertilizer application (3654 kg ha 21) at 200 kg N ha 21 but greater (p # 0.05) than control (1572 kg ha 21). Similar results were found with oat. The 200 kg N ha 21 liquid manure application continued to benefit crop growth in the second and third years. Solid manure did not influence biomass production of either crop in most crop/year combinations. Cumulatively, in 3 yr, smooth bromegrass recovered 59% of nitrogen from liquid manure, compared with 37% by oat. Soil Mehlich 3-P accumulation was found in some liquid and solid manure treatments for both crops. High soil exchangeable K was found in 1999 after liquid manure application but declined over time. Our results suggest that 100 kg N ha 21 liquid manure can replace nitrogen fertilizer at a similar rate. Liquid cattle manure was better than solid cattle manure in promoting bromegrass and oat production.
To optimize management, farmers require quantitative understanding of the factors aff ecting variability in soybean [Glycine max (L.) Merr.] seed yield and quality. Our objectives were to characterize spatial variation in soybean seed yield, oil concentration, and protein concentration in two south-central Minnesota fi elds over 6 yr of a corn [Zea mays L.]-soybean rotation, and to determine the infl uence of fertilizer treatments, soil chemical properties, and topography on soybean yield, oil, and protein. Soil and topographical variables were observed on 0.014-ha cells, and included Bray P1, Olsen P, K, Zn, pH, organic matter, total organic C, NH 4 -N, NO 3 -N, total N, mineralizable N, elevation, slope, curvature, fl ow accumulation, and aspect. Soybean yields consistently exhibited spatial structure. Within fi elds, spatial patterns of soybean yields were highly correlated across years, and we observed consistent relationships between yield and soil variables. Overall, soybean yield related positively to soil P and Zn and negatively to pH at all site-years. Models of soybean yield in relation to soil P and Zn indicate that in high pH soils at these sites, yield is optimized when soil P and Zn levels are higher than current extension recommendations. Protein and oil concentrations exhibited inconsistent spatial structure, and the spatial pattern of protein and oil concentrations diff ered across years. Relationships between soybean quality and soil properties were more consistent between sites within years than across years within sites, indicating that soybean quality is infl uenced by soil-climate interactions that function on a regional basis.
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