Nitrous oxide emissions from soil profiles seeded with pulse crops

Non-Peer ReviewedInoculation of legumes with Rhizobium spp. is a common worldwide agricultural practice that is used to increase crop yield and to improve soil fertility without adding nitrogen (N) fertilizers. There is concern that N2 fixation by legumes enhances emissions of nitrous oxide (N2O) – a powerful greenhouse gas (GHG). The objectives of this experiment were: 1) to measure N2O emissions from soil profiles under inoculated and non-inoculated pulse crops; 2) to investigate the relationship between N2O emissions and N2 fixation by pulse crops. The experiment was carried out in the Phytotron of the University of Saskatchewan with soil flats seeded with inoculated and non-inoculated lentils and peas and fertilized spring wheat. N2O emissions from soil profiles were measured using Profile Gas Samplers (PGS), and were analyzed with a GC. Results indicated that inoculated lentils and peas did not substantially increase N2O emissions, and N2O emissions may not be associated with N2 fixation under the conditions in this experiment

Nitrogen supply from belowground residues of lentil and wheat to a subsequent wheat crop

Non-Peer ReviewedLentil (Lens culinaris) plants can form an association with rhizobia and thereby biologically fix much of the nitrogen (N) required for their growth. This not only reduces the need for expensive N fertilizer when the lentil crop is grown, but there is a potential to contribute a net increment of N to the soil that can be utilized by the subsequent crop. However, estimating this net increment of N remains a challenge, because of the difficulty in estimating the amount of root and root-derived N. The purpose of this greenhouse study was to quantify the belowground N (BGN) of lentil and wheat (Triticum aestivum) using shoot 15N labeling and to trace the 15N from BGN into subsequently grown wheat plants. Belowground N comprised 34 and 51 % of total plant N in lentil and wheat, respectively. Biomass production and N uptake by wheat grown on lentil belowground residues (BGR) were 49 and 14 % higher than wheat grown on wheat BGR. Moreover, a higher proportion of added 15N from lentil BGN was recovered in the succeeding wheat crop, indicating that lentil BGN was more readily mineralized than wheat BGN. The disproportionately high increase in yield vs. N uptake for wheat grown on lentil BGR, however, indicates that non-N factors also contributed to the increase in wheat yield. This study highlights the importance of including estimates of BGN when evaluating the positive effects of including lentil crops in rotation with cereals

Influence of time and method of terminating alfalfa stands on soil N supply, crop yield, N uptake, soil organic C and N, and greenhouse gas emissions

Non-Peer Reviewe

Contribution of pulse crop residues and soil to N2O and CO2 emissions in a subsequent wheat crop: a 13C/15N study

Non-Peer Reviewe

Nitrogen effects on water use efficiency in the semi-arid Canadian prairies

Non-Peer ReviewedIn the semiarid environment of the Canadian prairies, water is the main constraint to crop production. Few studies have examined the influence of fertilizer on water use efficiency (WUE) and fewer still have made comparisons on a cropping system basis. We assessed the impact of fertilizer N on WUE in a 39-year crop rotation experiment conducted on a Brown Chernozemic soil at Swift Current, Saskatchewan. The cropping systems included continuous wheat (Cont W) with N+P and P fertilizer alone, and a fallow-wheat-wheat (F-W-W) system with N+P and P only. All cropping systems were managed using conventional tillage practices. We developed an equation to asses WUE of the cropping systems that included water use during the fallow year. We also calculated precipitation use efficiency (PUE, i.e., yield/harvest-to-harvest precipitation). WUE and PUE values and fertilizer effects were greatest in the later third of the study period, due to the increase in recommended fertilizer N rates applied and the more favorable moisture conditions that prevailed. We converted PUE results into net return values ($ha-1 mm-1 water) by assuming an average price over the 39-yr period and found that N fertilizer in the Cont W system earned an average return above fertilizer cost of$36.39 ha-1 yr-1 and $9.81 ha-1 yr-1in the F-W-W system

Agronomic and greenhouse gas assessment of land applied anaerobically digested swine manure

Non-Peer ReviewedManagement of animal wastes from intensive livestock operations (ILO) must be economically feasible, environmentally friendly and socially acceptable. Anaerobic digestion is a promising technology that could provide an option for managing animal waste that may reduce greenhouse gas emissions by utilizing the biogas produced during digestion to displace fossil-fuels and by reducing emissions during lagoon storage. A three-year study was conducted at two locations, Swift Current and Melfort, to compare the agronomic performance and gaseous N loss of land-applied anaerobically digested swine manure (ADSM) to conventionally treated swine manure (CTSM). Treatments included spring and fall applications of CTSM and ADSM at a 1x rate (10,000 and 7,150 L ha-1 respectively) applied each year, and a 3x rate (30,000 and 21,450 L ha-1 respectively) applied once at the beginning of the study. A treatment receiving commercial fertilizer (UAN) and a check (no N) were also included. Nitrogen use efficiency for single applications of ADSM or CTSM at the 3x rate were lower than three annual applications at the 1x rate, while UAN was intermediate. Nitrogen use efficiency of ADSM and CTSM applied in the fall was equal to spring when applied at 1x rate and, in general, agronomic performance of ADSM was similar or better than CTSM. Ammonia loss from ADSM was similar to CTSM, except for CTSM at the 3x rate applied in the fall at Melfort and in the spring at Swift Current, which had significantly higher losses than all other treatments. The percentage of applied N lost as N2O measured at the Melfort site was generally higher for treatments receiving CTSM compared to ADSM or UAN, and losses from ADSM and UAN were similar. The results from this study suggest that ADSM is equal or better than CTSM in terms of agronomic performance, but has lower environmental impact with respect to gaseous N loss

The impact of N-fertilizer management on N2O emissions in Saskatchewan

Non-Peer Reviewe

Influence of tillage, crop residue, controlled-release N fertilizer, and liquid swine manure management on greenhouse gas emissions in Saskatchewan, Canada

Non-Peer Reviewe

EC 11481-2303 - A Peculiar Subdwarf OB Star Revisited

EC 11481-2303 is a peculiar, hot, high-gravity pre-white dwarf. Previous optical spectroscopy revealed that it is a sdOB star with an effective temperature (Teff) of 41790 K, a surface gravity log(g)= 5.84, and He/H = 0.014 by number. We present an on-going spectral analysis by means of non-LTE model-atmosphere techniques based on high-resolution, high-S/N optical (VLT-UVES) and ultraviolet (FUSE, IUE) observations. We are able to reproduce the optical and UV observations simultaneously with a chemically homogeneous NLTE model atmosphere with a significantly higher effective temperature and lower He abundance (Teff = 55000 K, log (g) = 5.8, and He / H = 0.0025 by number). While C, N, and O appear less than 0.15 times solar, the iron-group abundance is strongly enhanced by at least a factor of ten.Comment: 8 pages, 11 figure