Abstract Eleven mulch treatments were evaluated during the fall of 1966 on a 2:1 northeast‐facing fill slope seeded to smooth bromegrass ( Bromus inermis Leyss.). Mulch materials included wood cellulose fiber, excelsior, jute netting, emulsifiable asphalt used separately and as an anchorage for corncobs, woodchips, prairie hay, and fiberglass. Plots protected with an excelsior mat yielded the best seedling grass. Eight mulch treatments were evaluated on a 2:1 east‐facing fill slope during the fall of 1967. Mulch materials included an emulsifiable polymer, compost, wood cellulose, jute netting, excelsior, and asphalt‐anchored mulches of excelsior, woodshavings, and bark dust. Plots protected with an excelsior mat or jute netting yielded the best seedling grass.
ABSTRACT: The interaction of various tillage and crop sequences on the distribution of soil organic carbon (C) and inorganic nitrogen (N) is important for predicting changes in soil physical and chemical properties and potential environmental impacts of soil and crop management. This study was conducted to determine the distribution of organic C, nitrate (NO3-N) and ammonium (NH4-N) in a soil with various tillage methods and crop sequences. A tillage experiment was started in 1978 with treatments of chisel, disk, no-till, plow, ridge-till, and sub-soil. In 1985, each tillage plot was divided into two subplots to which two crop sequences of continuous corn [Zea mays L.] (C-C), and soybean [Glycine max (L.) Merr.]-corn (S-C) were assigned. Nitrogen fertilizer was applied at a rate of 100 kg N ha−1 y−1 when plots were planted to corn. In the spring and autumn of 1989, soil samples were taken from crop sequences and tillage plots to a depth of 1.5 m in 0.3 m increments for determination of NOTN, and NH4-N contents. Soil samples were also collected from 0–10, 10–20, 20–40, 40–60, 60–80, 80–100, 100–150, 150–200, 200–250, and 250–300 mm soil depths for organic C determination. Multivariate analysis of variance (MANOVA) was used to analyze the data taken from different soil depths. Organic C concentration was greatest at 0–10 mm soil and decreased with increasing soil depth. Organic C was greatest for no-till and was least for sub-soil. Greater residue in C-C was associated with greater soil organic C than S-C. Organic C quantity (kg ha−1 300 mm−1) followed the same trend as organic C concentration. The plow treatment had the greatest NOTN quantity in the 0–0.3 m soil depth. All tillage systems had similar NO3-N amounts in deeper soil. NH8-N content of soil was not influenced by tillage or crop sequences. Soil organic C was related to both the amount of residue produced and left on the soil surface after harvest and also to the degree of soil surface disturbance. Nitrate-N was affected more by tillage and crop sequence systems than was ammonium-N.
ABSTRACT CONTINUOUS use of no-till planting systems may result in reduced yields, especially on finer textured soils that tend to be poorly drained. Soil compaction and poor soil aeration have been identified as possible factors contributing to the lower yields. Research conducted to evaluate tillage rotations on these soils shows that periodic use of the moldboard plow can result in statistically higher yields as compared to continuous no-till. However, use of chisel plow and disk tillage systems following three years of continuous no-till did not result in yield increases. A relationship between cone penetrometer index and yield indicates a trend toward lower yield with higher index values with continuous no-till having the highest index.
Abstract Differences in traffic and tillage intensity among positions in ridge tillage create distinctly different environments for microbial activity. This study was conducted to assess the impact of long‐term controlled wheel traffic on soil respiration in ridge‐till and to use correlation analysis to identify relationships between soil respiration and soil physical and chemical properties. Soil respiration was evaluated from 0 to 30 cm in one row, one tractor‐trafficked interrow, and one nontrafficked interrow of continuous corn ( Zea mays L.) and continuous soybean [ Glycine max (L.) Merr.]. Soil respiration was measured on disturbed samples at three levels of water‐filled pore space (WFPS) by gas chromatography for 25 d. Properties assessed included bulk density, soil strength, texture, aggregate‐size distribution, saturated hydraulic conductivity ( K sat ), water retention characteristics, organic C, and total N. Soil respiration was greatest at 0 to 7.5 cm in each position and decreased significantly below that depth. Correlation analysis indicated microbial activity in ridge‐till varied spatially in relation to changes in the soil physical environment. Soil respiration was negatively correlated with bulk density at each WFPS. The K sat was positively correlated with soil respiration at 0 to 7.5 cm for each WFPS. Under drier soil conditions, as exemplified by 47% WFPS, aggregates <1.0 mm and gravitational water were positively correlated with soil respiration at the 0 to 7.5 cm. Soil environments characterized by bulk density <1.4 Mg m −3 and K sat >10 cm h −1 were associated with respiration rates >4 and 12 mg CO 2 ‐C L −1 soil d −1 , respectively.
Abstract Soil core samples from four abandoned beef cattle feedlots were analyzed to determine their chemical and physical characteristics. These cores were compared with those from active upland, intermittently used feedlots, and croplands. The nitrate‐nitrogen (NO 3 ‐N) in the abandoned feedlots averaged 7,200 kg/ha in a 9.1‐m soil core, while the active upland, intermittently used feedlot, and cropland averaged 1,800, 2,100, and 570 kg/ha NO 3 ‐N, respectively. The abandoned feedlot core with the highest NO 3 ‐N had 18,200 kg/ha in a 9.1‐m core. Nitrate‐N levels in an abandoned feedlot after 15 years of corn‐alfalfa rotation were comparable with cropland cores. Ground‐water samples obtained from three of the four abandoned feedlots contained 77.2, 43.7, and 0.6 ppm NO 3 ‐N.
Abstract Leaching of atrazine [2‐chloro‐4‐(ethylamino)‐6 (isopropylamino‐ s ‐triazine] was measured from the soil surface to below the root zone in an irrigated field under continuous corn ( Zea mays L.). The field was located in the Platte River Valley of central Nebraska in the central Great Plains area of the USA. This nearly level site is typical of the Platte River Valley with a coarse‐ to medium‐textured soil of alluvial origin that contains low levels of organic matter, and with a water table at a 5‐m depth. Vacuum soil water extractors located 1.5 m below the soil surface recovered an average of 0.072% of the atrazine applied to the surface during 1979 and 1980. Analysis of groundwater recovered from wells on opposite ends of the experimental field indicated enrichment with atrazine in the direction of the hydraulic gradient. Results support direct downward leaching as largely responsible for the low‐level atrazine contamination detected in groundwater throughout the irrigated corn production areas of the valley.
ABSTRACT Often a tillage machine is needed that maintains plant residue on the soil surface for erosion control and water conservation while simultaneously destroying tillage pan or soil compaction beneath. To accomplish this, a sweep blade 1.7 m wide was modified by mounting specially designed 150 mm steel shanks below the blade to fracture soil. Shanks were designed with a bend and twist to force soil to the side and up at a 15 angle from horizontal to fracture the interface between the tilled and untilled soil. Shanks had left and right orientations and were mounted in pairs with two or four shanks per sweep blade, covering about 80% of the sweep blade width. The fractured lower soil boundary was an irregular corrugated-shaped cross section in contrast to a flat sheared soil surface under the blade. Compared to the sweep blade alone, draft requirements increased about 85% with two shanks and by another 20% to 30% when four shanks were used. The surface soil layer was tilled by the sweep blade (SBT) and plant residue was kept on the surface. In the shank tilled (ST) layer below the sweep, soil bulk densities were significantly decreased relative to those for untilled soil (UT) at the same depth, indicating that shanks were effective in destroying tillage pans and effective in creating a fractured irregular pattern at the bottom of ST zone. Decreased bulk density in the ST zone provides space for soil water storage during precipitation events and the fractured irregular soil interface provides potential for greater infiltration of water.
