Long and short-term variability of aggregate size distribution in tillage and chemical fallow

Non-Peer ReviewedSize distribution of aggregates is one of the most important factors which affect soil erodibility with respect to wind erosion. A long-term study was established in 1968 to investigate the influence of tillage and chemical fallow systems on aggregate size distribution. The cropping systems involved fallow with herbicides only, herbicides in combination with one or two tillage operations, and tillage alone. Significant differences in aggregate size distribution were found between years during the period between 1968 and 1986. It was clear that in some years Melfort soils were highly erodible. In 1991, aggregate size distribution was measured at 5 times during the fallow season in order to evaluate the effects of the different cropping systems, determine aggregate size distribution with depth, and to compare variability over the long and short term. The percentage of aggregates at the surface in the 0 to 0.5 mm size fraction decreased after tillage with a double disk, and increased with time thereafter despite further cultivation with a field cultivator, but remained relatively constant under chemical fallow. During the period of this study it was clear that there were two distinct sources of variability in soil erodibility. Both sources of variability should be taken into account if soil erodibility is to be predicted over the long term

Ammonia volatilization from manure in cropping systems for ethanol production

Non-Peer ReviewedEffect of tillage on ammonia (NH3) volatilized from fresh and com posted farmyard manure (FYM) used for fertilizing barley (Hordeum vulgare L.), was determined at two sites near Melfort, Saskatchewan in 1993. Ammonia losses were markedly higher in plots under zero tillage than under conventional tillage, as well as in plots which received a high rate (90 t ha-1) of FYM versus a lower rate (22 t ha-1). In conservation tillage cropping systems in which FYM is not incorporated into soil, the amount ofNH3 volatilized is not very large when FYM-N rates are comparable to crop requirements

Tolerance of field peas to graminicides and metribuzin combinations

Non-Peer ReviewedTolerance of two cultivars of field peas (Pisum sativum L.) to sethoxydim, fenoxaprop-P-ethyl, clethodim, fluazifop-P-butyl and haloxyfop, and their combinations with metribuzin was investigated in 1987, 1988, and 1989. Both Trapper and Victoria peas exhibited satisfactory tolerance to metribuzin (0.21 kg a.i. ha-1 ) and the graminicides when tested alone. However, tank mixed treatments caused some crop injury which sometimes affected pod maturity and seed yield. Tank mixes significantly reduced Victoria yield by 7 % compared to graminicides alone. Trapper yield was not significantly reduced. The increased injury observed with metribuzin when tank mixed, was attributed to the use of adjuvants, required for enhancing graminicidal activity, which may have increased foliar uptake of metribuzin by peas. The adverse effect of metribuzin in tank mixes was more pronounced on both cultivars in 1988 when it was exceptionally hot and dry

Performance of annual legume green manure crops at Saskatoon

Non-Peer ReviewedFour annual legumes, lentil (Lens culinaris cv. 'NEL-481'), field pea (Pisum sativum cv. 'Trapper'), faba bean (Vicia faba cv. 'Outlook'), Tangier flatpea (Lathyrus tingitanus cv. 'Tinga'), and one perennial, alfalfa (Medicago sativa cv. 'Moapa') were compared over three growing seasons for their suitability as annual green manure crops grown in the fallow year of a wheat-fallow rotation. As nitrogen-fixation usually declines after seed set, crop growth was stopped by cultivation or desiccation during early pod filling. This terminated further use of available soil moisture, conserving it for the following grain crop. Mean seasonal nitrogen fixation ranged from 2 to 40 kg/ha. However, the mean total nitrogen in the top growth at plow down, ranged from 15 to 114 kg/ha. The measured nitrogen fixation accounted for 13 to 42 % of the above ground nitrogen. There was little difference in water use among the legume crops

Spring wheat rotations in north-central Saskatchewan

Non-Peer ReviewedEffects of rotation length, crop sequence, and fertilization on yields and economic performance of 10 spring wheat-based rotations are examined over a 27-year period (1960-86) on an Orthic Black Chernozem at Melfort, Saskatchewan. The silty clay loam soil had an initial organic N content of about 0.55 % (0-15 cm depth). During 1960-71, fertilized plots received N and P based on general recommendations for the region; thereafter, fertilizer was applied based on soil tests. Yields of wheat grown on fertilized fallow were similar for F-W, F-W-W and a 6-yr fallow-wheat-legume hay (F-W-W-H-H-W) rotation (avg 2519 kg ha-1 in 1960-71 and 3036 kg ha-1 in the wetter 1972-86 period). Fertilized stubble wheat yields in a F-W-W rotation averaged 88 % of comparable fallow wheat yields, while continuous wheat averaged only 66 % due to greater weed and disease problems. Inclusion of grass-legume hay or legume green manure crops in the rotations provided no yield benefit for subsequent wheat crops in this fertile soil. Results of the economic analysis showed that at wheat prices greater than $147 t-1, fertilized F-W-W, F-C-W and F-W-W-H-H-W generally provided the best overall economic return. At lower wheat prices unfertilized F-W-W and F-W-W-H-H-W, and fertilized F-W often provided the highest net income. It was profitable to substitute canola for wheat grown on conventional fallow or on partial fallow after grass-legume hay when the ratio of canola to wheat price was greater than about 2.0. Similarly, it was profitable to include grass-legume hay in wheat rotations when the hay price was greater than about one-half that of wheat. Continuous wheat and legume green manure rotation were not economically competitive with the best rotations at any of the price options examined. Fertilizer application was profitable in the F-W-W and continuous wheat rotations when the ratio of fertilizer N cost to wheat price was less than about 5.0; it was profitable in F-W-W-H-H-W when this ratio was less than 3.5. The cost of producing wheat, income variability, and the frequency of economic losses increased with cropping intensity

Fertilizer application and deep leaching of nitrate under long term crop rotation

Non-Peer ReviewedIt is commonly believed that the use of nitrogen fertilizers in agriculture will lead eventually to the loss of nitrate via leaching. The nitrate leached below the root zone has the potential to contaminate underground water. The results obtained from various long term crop rotation studies in Saskatchewan suggest that this common belief may not hold in general. This is especially true where nitrogen fertilizers were applied based on soil test recommendation and the land was continuously cropped. Under long term crop rotation studies in the Black Soil Zone at Melfort, the application of nitrogen fertilizer in recent years were based on the general recommendation for wheat. The deep core sample revealed that more nitrate was present in the soil profile under fertilized continuous wheat compared to the unfertilized plots. However, in the Black Soil at Indian Head, where fertilizer application was based on soil test values, similar amounts of nitrate were found below the root zone of fertilized and unfertilized plots after 34 years of continuous wheat. This was in spite of applying 1584 kg of N ha-1 to the fertilized plot over 34 years. A result similar to that at Indian Head was obtained from the crop rotation experiment in the Brown Soil Zone at Swift Current. In the Brown Soil Zone, the inclusion of a fallow phase in the rotation, increased the amount of nitrate found below the root zone although this system had received less fertilizer over the years than the continuously cropped plots. The fallow phase appeared to provide a window for the leakage of nitrate accumulated within the root zone. This was attributed to a better moisture (antecedent moisture) regime and higher amount of mineralized nitrate during the fallow phase. On the other hand, frequent summerfallow can deplete the soil of its N supplying power and this may eventually result in less nitrate leached as was found for the 2-yr rotation at Indian Head after 34 yr

The long-term agronomic and economic effects of crop rotations in western Canada

Non-Peer ReviewedAgriculture Canada Research Stations in western Canada have conducted more than 68 long-term crop rotation experiments since the early 1900's; twenty of these are still ongoing. A committee of scientists, representing all Research Stations on the Prairies has just completed an in-depth review and summary of the major findings from these studies. Based on their findings, they also developed recommendations that can be used by managers in decision making and rationalization of resource use for current and future studies of this kind. The resulting two publications which will be released in early 1990 include: i) a bulletin entitled 'Benefits of Crop Rotation for Sustainable Agriculture in Dryland Farming', 'Which presents producer recommendations on how to run an efficient, economical, and environmentally responsible cropping operation, and ii) a detailed technical book entitled 'Crop Rotation Studies on the Canadian Prairies', which is directed at the scientific community but is also useful for extension personnel and producers. This paper highlights some of the main aspects reported in these publications and attempts to give a coherent and broader interpretation of the underlying principles and processes of crop production. The discussion focuses on the effects of rotation length, crop sequence, substitutes for summerfallow, and N and P fertilizer, on crop production, grain and forage quality, soil moisture conservation and moisture use efficiency, N and P uptake by the plants, nutrient losses, soil quality, profitability, nonrenewable energy efficiency, and crop pests