• Authors:
    • Campbell, C. A.
    • Kirkwood, V.
    • Gregorich, E. G.
    • Monreal, C.
    • Tarnocai, C.
    • Desjardins, R. L.
    • Dumanski, J.
  • Source: Climatic Change
  • Volume: 40
  • Issue: 1
  • Year: 1998
  • Summary: Increasing carbon sequestration in agricultural soils in Canada is examined as a possible strategy in slowing or stopping the current increase in atmospheric CO2 concentrations. Estimates are provided on the amount of carbon that could be sequestered in soils in various regions in Canada by reducing summerfallow area, increased use of forage crops, improved erosion control, shifts from conventional to minimal and no-till, and more intensive use of fertilizers. The reduction of summerfallow by more intensive agriculture would increase the continuous cropland base by 8.1% in western Canada and 6.8% in all of Canada. Although increased organic carbon (OC) sequestration could be achieved in all agricultural regions, the greatest potential gains are in areas of Chernozemic soils. The best management options include reduction of summerfallow, conversion of fallow areas to hay or continuous cereals, fertilization to ensure nutrient balance, and adoption of soil conservation measures. The adoption of these options could sequester about 50-75% of the total agricultural emissions of CO2 in Canada for the next 30 years. However, increased sequestration of atmospheric carbon in the soil is possible for only a limited time. Increased efforts must be made to reduce emissions if long-term mitigation is to be achieved.
  • Authors:
    • Zuberer, D. A.
    • Hons, F. M.
    • Franzluebbers, A. J.
  • Source: Soil & Tillage Research
  • Volume: 47
  • Issue: 3-4
  • Year: 1998
  • Summary: Quality of agricultural soils is largely a function of soil organic matter. Tillage and crop management impact soil organic matter dynamics by modification of the soil environment and quantity and quality of C input. We investigated changes in pools and fluxes of soil organic C (SOC) during the ninth and tenth year of cropping with various intensities under conventional disk-and-bed tillage (CT) and no tillage (NT). Soil organic C to a depth of 0.2 m increased with cropping intensity as a result of greater C input and was 10% to 30% greater under NT than under CT. Sequestration of crop-derived C input into SOC was 22+-2% under NT and 9+-4% under CT (mean of cropping intensities +- standard deviation of cropping systems). Greater sequestration of SOC under NT was due to a lower rate of in situ soil CO2 evolution than under CT (0.22+-0.03 vs.0.27+-0.06 g CO2-C g-1 SOC yr-1). Despite a similar labile pool of SOC under NT than under CT (1.1+-0.1 vs. 1.0+-0.1 g mineralizable C kg-1 SOC d-1), the ratio of in situ to potential CO2 evolution was less under NT (0.56+-0.03) than under CT (0.73+-0.08), suggesting strong environmental controls on SOC turnover, such as temperature, moisture, and residue placement. Both increased C sequestration and a greater labile SOC pool were achieved in this low-SOC soil using NT and high-intensity cropping.
  • Authors:
    • Wagner, G. H.
    • Buyanovsky, G. A.
  • Source: Global Change Biology
  • Volume: 4
  • Issue: 2
  • Year: 1998
  • Summary: Long-term data from Sanborn Field, one of the oldest experimental fields in the USA, were used to determine the direction of soil organic carbon (SOC) dynamics in cultivated land. Changes in agriculture in the last 50 years including introduction of more productive varieties, wide scale use of mineral fertilizers and reduced tillage caused increases in total net annual production (TNAP), yields and SOC content. TNAP of winter wheat more than doubled during the last century, rising from 2.0-2.5 to 5-6 Mg ha(-1) of carbon, TNAP of corn rose from 3-4 to 9.5-11.0 Mg ha(-1) of carbon. Amounts of carbon returned annually with crop residues increased even more drastically, from less than 1 Mg ha(-1) in the beginning of the century to 33.5 Mg ha(-1) for wheat and 5-6 Mg ha(-1) for corn in the 90s. These amounts increased in a higher proportion because in the early 509 removal of postharvest residues from the field was discontinued. SOC during the first half of the century, when carbon input was low, was mineralized at a high rate: 89 and 114 g m(-2) y(-1) under untreated wheat and corn, respectively. Application of manure decreased losses by half, but still the SOC balance remained negative. Since 1950, the direction of the carbon dynamics has reversed: soil under wheat monocrop (with mineral fertilizer) accumulated carbon at a rate about 50 g m(-2) y(-1), three year rotation (corn/wheat/clover) with manure and nitrogen applications sequestered 150 g m(2) y(-1) of carbon. Applying conservative estimates of carbon sequestration documented on Sanborn Field to the wheat and corn production area in the USA, suggests that carbon losses to the atmosphere from these soils were decreased by at least 32 Tg annually during the last 40-50 years. Our computations prove that cultivated soils under proper management exercise a positive influence in the current imbalance in the global carbon budget.
  • Authors:
    • Izaurralde, R.
    • Gill, K.
    • Arshad, M.
  • Source: Journal of Sustainable Agriculture
  • Volume: 12
  • Issue: 2/3
  • Year: 1998
  • Summary: Properties of a silt loam (Dark Gray Luvisol), weed population and wheat production ( Triticum aestivum) in canola ( Brassica campestris)-wheat-wheat (C), fallow-wheat-wheat (F), field pea ( Pisum sativum)-wheat-wheat (P) and continuous wheat (W) cropping systems were compared under conventional tillage (CT) and no-till (NT) in field trials near Beaverlodge, Alberta, Canada. Percentage of water stable aggregates (WSA) was reduced after a fallow season. Soil NO 3-N was similar among cropped plots which was significantly lower than fallow plots in two of the three years. Ammonium-N, extractable P and penetration resistance (PR) of soil were not affected by crop rotation. The W plots tended to have more weeds than both the first (W1) and second (W2) year wheat plots in rotations. Wheat appeared to suppress weeds better than canola, field pea or fallow. Average annual production of 3.95 t/ha as grain and 10.7 t/ha as above-ground dry matter (AGDM) by W1 were significantly greater than the corresponding production by W2 and W. Wheat grain and AGDM production in the two years of C, F, P and W systems were not significantly different in most cases. However, cumulative yields by C, P and W systems for three years of rotation were greater than the corresponding grain and AGDM yields from F rotation by 1.10-4.19 and 4.3-8.7 t/ha, respectively. Tillage did not affect NO 3-N, NH 4-N, P and WSA in soil but reduced its PR. The NT system provided better control of annual broadleaf weeds whereas perennial weeds were better controlled by CT. The CT system produced more grains (average of 0.42 t/ha per year) than NT system. Crop rotation by tillage interaction effects on soil properties, weed populations and crop yields were not significant which indicated that the crop rotations were equally effective under both the tillage systems. Benefits of crop rotation over monoculture in this study were of similar nature as in earlier studies conducted on fields already under annual cropping systems. Canola and field pea were more beneficial than wheat as previous-crop for wheat production. Replacing fallow with a crop resulted in increased crop production and straw returned to soil, reduced potential for leaching of NO 3-N, and improved water stable aggregation of soil.
  • Authors:
    • Gordon, WB
    • Maddux, LD
    • Rice, CW
    • Omay, AB
  • Source: Soil Science Society of America Journal
  • Volume: 62
  • Issue: 6
  • Year: 1998
  • Summary: Increasing crop N use efficiency and minimizing environmental risk require an accurate assessment of N taken up by the crop from different sources. We conducted this study to: (i) compare the grain yields of corn (Zea mays L.) in monoculture and in rotation with soybean [Glycine max (L,) Merr,]; (ii) determine the contributions of N from fertilizer, soil, and legume residue to corn in the rotation; and (iii) compare N fertilizer recovery in monoculture and in rotation. Two existing (>10 yr) irrigated corn-soybean rotation areas in Kansas were used. The soils were Crete silt loam (fine, smectitic, mesic: Pachic Argiustolls) and Eudora loam (coarse-silty, mixed, superactive, mesic Fluventic Hapludolls). To trace the N through the rotation, N-15 microplots (2.4 m(2)) were established in the corn. Microplots also Here established in soybean to separately follow N-15 from roots + soil and shoots to corn. Crop rotation and fertilizer addition increased corn yield at both sites for two growing seasons. Averaged for 2 yr, the amount of N needed in the continuous corn to achieve yield equal to that in rotation with no N added was equivalent to 144 kg N ha(-1) in the Crete silt loam and 155 kg N ha(-1) in the Eudora loam, Response to N was greater on the Eudora loam, probably because of textural and organic matter differences. In the Eudora soil, significantly higher amounts of soil N Here taken up at harvest by corn in rotation, whereas, in the Crete soil, corn in monoculture took up significantly higher amounts of soil N, Corn plants recovered 3 kg N ha(-1) (3%) from soybean residue in the Eudora soil and 5 kg N ha(-1) (14%) in the Crete soil. The main value of legume residue appears to be longterm maintenance of soil N to ensure adequate delivery to future crops.
  • Authors:
    • Doran, J. W.
    • Koerner, P. T.
    • Power, J. F.
    • Wilhelm, W. W.
  • Source: Soil Science Society of America Journal
  • Volume: 62
  • Issue: 5
  • Year: 1998
  • Summary: Returning crop residue improves water conservation and storage, nutrient availability, and crop yields, We have little knowledge, however, er, of the residual impacts of crop residues on soil properties and crop production. We hypothesized that residual impacts of crop residues vary with the amount of residues used. A 10-yr study near Lincoln, NE, evaluated the residual effects of an earlier 8-yr study of various crop residue amounts on crop growth and selected soil properties. From 1978 through 1985, crop residues were returned at 0, 50, 100, and 150% of the quantity produced by the previous crop (averaging 0 to approximate to 6 Mg ha(-1) yr(-1)). Continuous corn (Zea mays L.) was produced 1986 through 1995 on these plots, except sorghum [Sorghum bicolor (L.) Moench] was substituted in several years. To study management effects on residual responses, plots were subdivided with or without tillage, N fertilizer (60 kg N ha(-1)), and hairy vetch (Vicia villosa L.) cover crop. Residual effects of the 150% residue amount increased grain production 16% compared with the 0% amount (4900 vs. 4250 kg ha(-1), respectively), and were not affected by time or other management practices. Increasing previous residue amount did enhance soil N availability (from 73.0 to 82.3 kg autoclave-mineralizable N ha(-1)) and Bray soil P (16.7 to 20.3 kg ka(-1)). These results are among the first to show that residual effects of crop residue are prolonged (half-life of approximate to 10 yr) and probably result from changes in soil properties that enhance soil nutrient availability.
  • Authors:
    • Kolberg, R. L.
    • Rouppet, B.
    • Westfall, D. G.
    • Peterson, G. A.
  • Source: Soil Science Society of America Journal
  • Volume: 61
  • Issue: 2
  • Year: 1997
  • Summary: Direct quantitative measurement of soil net N mineralization in agricultural soils under field conditions has not been widely used. A potential method of in situ net N mineralization was investigated in the fallow phase of a 3-yr no-till crop rotation at two sites. Undisturbed soil cores (5 by 15 cm) with anion- and cation-exchange resins (Sybron Ionac ASB-1P and C-249) at the bottom were incubated in situ. Nitrate-N plus NH4+-N extracted from soil was added to extracted amounts from resin bags to determine net N mineralized during each of three incubation periods (3-4 wk each). Total net N mineralization was 33.7 and 26.5 kg N ha(-1) during 84 and 75 d of incubation at Sterling and Stratton, respectively. Relative amounts of resin did not affect N captured but cores placed midway between old corn (Zea Mays L.) rows tended to accumulate more (P > F = 0.13) N than cores placed in rows. This in situ method appears to be a reliable method for measuring net N mineralization in the field; however, variation is large and many observations are required to obtain net N mineralization rates within an acceptable confidence interval.
  • Authors:
    • Peterson, G. A.
    • Westfall, D. G.
    • McGee, E. A.
  • Source: Journal of Soil and Water Conservation
  • Volume: 52
  • Issue: 2
  • Year: 1997
  • Summary: Wheat-fallow (W-F) is the predominant cropping system in the Great Plains, but the percent of precipitation stored as soil water (WSE) during fallow is frequently less than 25% with conventional tillage. No-till technology has improved potential WSE. Our objectives were to determine the effects of cropping system, landscape position (soil), and evaporative gradient (location) on WSE during inter-crop periods in intensified no-till cropping systems. Water storage efficiency was 48% during the wheat to corn fallow period in the 3- or 4-year rotational systems, contrasting sharply with the 22% WSE for the W-F system. The 3-year system, with a shorter fallow period (11 months), was just as effective in storing water as the long fallow period (14 months) in the WF system. Water storage efficiency was the lowest at the southern location, which had the highest potential evapotranspiration, but the contrasts among cropping systems remained. Toeslope soils had the highest WSE compared to summit or sideslope positions because of their opportunity to catch runoff water. The possibility exists for using even move intensive cropping systems than those examined in this study and this may mean that summer fallow could be eliminated with no-till practices.
  • Authors:
    • Norwood, C.
    • Currie, R.
  • Source: Journal of Production Agriculture
  • Volume: 10
  • Issue: 1
  • Year: 1997
  • Summary: Dryland crop yields in the U.S. Great Plains are limited by low precipitation and high potential evapotranspiration. In western Kansas wheat (Triticum aestivum L.) and grain sorghum [Sorghum bicolor (L.) Moench] are grown commonly, whereas corn (Zea mays L.) is believed to lack sufficient drought and heat tolerance for dryland production. A study was conducted near Garden City, KS, from 1991 through 1995 to determine whether corn could be grown successfully. No-till (NT) and conventional-till (CT) corn and grain sorghum were compared. In the driest year, sorghum yielded 137% more than corn with CT and 85% more with NT, but in 3 of 5 yr, NT corn yielded from 34% to 112% more than NT sorghum. In the remaining year, CT sorghum yielded more than CT corn, but NT yields did not differ. Overall, NT increased corn yields by 28% and net return by 69%, but increased sorghum yields by only 11% add had no effect on net return. No-till corn yielded 28% more than NT sorghum and produced 169% more net return, whereas CT corn yielded 11% more than CT sorghum and produced 48% more net return. Dryland corn can be grown in western Kansas if lower yields and returns are accepted in dry years in exchange for yields and returns considerably higher than those of sorghum in favorable years. No tillage will substantially increase yields in most years and is essential to assure adequate corn yields in dry years.
  • Authors:
    • Papendick, R.
    • Parr, J.
  • Source: Annals of Arid Zone
  • Volume: 36
  • Issue: 3
  • Year: 1997
  • Summary: Most dryland fanning systems depend an tillage to grow crops. There is overwhelming evidence that repeated tillage is destroying the soil resource base and causing adverse environmental impacts. Tillage degrades the fertility of soils, causes air and water pollution, intensifies drought stress, destroys wildlife habitat, wastes fuel energy, and contributes to global warming. Consequently, most tillage-based systems in a dryland environment are not sustainable in the long-term. Today, dryland farmers are expected to produce food in ever greater quantities. This is becoming more difficult to do in view of declining soil quality, most of which is caused by soil tillage. It is becoming well documented scientifically that continuous no-till is the most effective, and practical approach for restoring and improving soil quality which is vital for sustained food production and a healthy environment. With this way of farming crop, residues or other organic amendments are retained on the soil surface and sowing/fertilizing is done with minimal soil disturbance. Research and farmers' experience indicate that with continuous no-till soil organic matter increases, soil structure improves, soil erosion is controlled, and in time crop yields increase substantially from what they were under tillage management, due to improved water relations and nutrient availability. These changes help to promote a cleaner and healthier environment and a more sustainable agriculture. A major obstacle that farmers often face with change to continuous no-till is overcoming yield-limiting factors during the transition years, that is, the first years of no-till following a history of intensive conventional tillage. These factors are often poorly understood and may be biologically-driven. Some of the problems involve residue management and increased weed and disease infestations. Farmer experience seems to indicate that many problems during the transition are temporary and become less important as the no-till system matures and equilibrates. The judicious use of crop rotations, cover crops and same soil disturbance may help reduce agronomic risks during the transition years. Farmers switching to continuous no-till must often seek new knowledge and develop new skills and techniques in order to achieve success with this new and different way of farming. Answers to their questions are urgently needed to provide strategies far promoting no-till as a way to enhance agricultural sustainability for future generations.