ALBERT

Description: The reclamation success of abandoned wellsites in agricultural areas depends on their capacity to sustain levels of biomass production similar to those which existed prior to soil disturbance. We examined the effect of four (0, 50, 100 and 150%) topsoil replacement depths (TRD) and five amendment treatments [compost, manure, alfalfa (Medicago sativa L.) hay, wheat (Triticum aestivum L.) straw, check) in the reclamation of three wellsites in south-central Alberta. The largest incremental effect of TRD on spring wheat response in the 4 yr (1997-2000) study occurred between the 0 and 50% treatments. Increasing TRD from 100 to 150% had little impact on crop response. Of the 20 treatments (four TRD × five amendments), the reclamation capacity of the 100% TRD-compost treatment ranked highest, being 19% higher than the baseline treatment (100% TRD-check). The lowest-ranking treatment overall , was the 0% TRD-straw treatment, which yielded 64% of the baseline treatment. Crop yield responses to organic amendments were larger when the recipient soil was lower in organic matter. Positive responses to one-time applications of organic amendments in the short-term (4 yr), advocate their use in soil reclamation of abandoned wellsites, despite a lingering question about the longevity of their beneficial effects. Key words: Soil reclamation, topsoil, organic amendments, natural gas wellsite

Description: Now, as a new century begins, may be a good time to reflect on the future of Soil Science on the Canadian prairies. One way to do that is to step back about one hundred years, to the turn of the previous century when our grassland soils were first cultivated. What questions perplexed scientists then? And how did they look for answers? My objective is to listen for our forebears’ thoughts in their writings, now largely buried. From this historical vantage may emerge insights, not only into where our science has been, but also into where it might yet go. Key words: Soil organic matter, crop rotation, grassland soils, history

Description: Leonardite, an oxidized form of lignite obtained from coal mines, is readily available and high in humic acids (HA). It has potential as a soil amendment and may have positive effects on crop growth and yield. This greenhouse experiment evaluated the agronomic effect of leonardite on three crops: canola (Brassica napus), wheat (Triticum aestivum) and green beans (Phaseolus vulgare). The factorial design combined five rates of leonardite with five fertility treatments. The fertility treatments had a significant effect on the dry matter yield (DMY) of canola, wheat and green beans. There were also significant effects of fertility on the concentration and uptake of N, P and K by the three crops and S by canola. The application of leonardite had no significant effect on the DMY of wheat and green beans but that of canola was significantly increased. Application of 10 g of leonardite to 3 kg of soil caused a 27% increase in the DMY of canola when S was excluded from added nutrients, while 1 g of leonardite resulted in a 15% increase in yield when all nutrients were applied. In addition, uptake of S, N, P and K by canola were significantly affected by the application of leonardite. The yield response of canola was apparently due to the supply of S by leonardite with an increasing rate of leonardite supplying increasing amounts of S. This result was confirmed in a second experiment where high quantities of leonardite were applied. We concluded that leonardite increased the yield of canola by supplying S directly and by possibly facilitating the uptake of other nutrients. The lack of response of wheat and green beans to leonardite was attributed to their lack of response to S. The experiment showed beneficial effects of leonardite on canola, though high rates may be needed to exploit this benefit in field situations. Key words: Leonardite, humic acid, green house, canola, fertility

Description: Maximum sequestration of atmospheric C in agricultural soils of the Canadian prairies can be achieved by the replacement of crop rotations that include summer fallow with continuous cropping or perennial forages. However, few studies have documented potential gains of soil organic C (SOC) in the region with the greatest use of fallow, the Brown soil zone. A dryland crop rotation study was initiated in 1992 on a Chin clay loam (Orthic Brown Chernozem) in southeastern Alberta on a site that had previously been under conventional irrigated cereal production. The study included fertilized and unfertilized treatments of the following crop rotations: fallow-wheat (FW), fallow-wheat-wheat (FWW), continuous wheat (W) and grass (G). The grass rotation consisted of pubescent wheatgrass (Agropyron trichophorum) harvested for hay. Total organic-, light fraction- and 10-wk mineralized-C and -N were determined in fall 1997, 6 yr after study initiation. Growing season precipitation (April through August) was 43% above long-term normals in the first 2 yr of this study, supporting excellent grass establishment and high crop yields, but was below normal thereafter. Fertilization with N and P increased average rotation yields by 21 to 56%, with the greatest yield increases in the G and W rotations. Total SOC to 15 cm (equivalent mass basis) was 1.5 Mg ha-1 higher (P = 0.03) in the W rotation and 3.0 Mg ha-1 higher (P = 0.0001) in the G rotation than in the FW rotation, but was not affected by fertilizer treatment or the interaction of fertilizer and crop rotation treatments. Low variability in measured SOC allowed us to detect differences as low as 1.3 Mg ha-1 among crop rotations, demonstrating that small effects of crop management on SOC can be detected using appropriate methods at uniform sites. Much of the gain in SOC in the G treatment was in mineralizable and light fraction material, indicating that this gain in SOC would be readily lost upon reversion to annual cropping. A simple calculation of residue C inputs and conversion to SOC showed that most of the gain in SOC in the W treatment was due to increased crop residue inputs, but that both increased inputs and reduced decomposition rates likely affected SOC gains in the G treatment. The average gain in SOC during the 6-yr period of this study was 0.25 Mg ha-1 yr-1 due to the elimination of fallow and 0.5 Mg ha-1 yr-1 due to establishment of a perennial forage. Key words: Soil organic matter, carbon sequestration, summer fallow, light fraction