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W D Reynolds

Publications and source records attributed to W D Reynolds.

8 recordsLinked to original sources
PubMed2002

Effect of long-term conventional tillage and no-tillage systems on soil and water quality at the field scale.

No-tillage (NT) is becoming increasingly attractive to farmers because it clearly reduces soil erosion and production costs relative to conventional tillage (CT). However, the impacts of no-tillage on the quantity and quality of tile drainage water are less well known. Accordingly, two adjacent field scale on-farm CT and NT sites were established to compare the impacts of the two tillage systems on tile drainage and NO3-N loss in tile drainage water. The effect of the two tillage systems on soil structure, hydraulic conductivity, and earthworm population were also investigated. The total NO3-N loss in tile drainage water over the 5-yr period (1995-1999) was 82.3 kg N ha(-1) for the long-term NT site and 63.7 kg N ha(-1) for the long-term CT site. The long-term NT site had 48% more tile drainage (6,975 kL ha(-1)) than the long-term CT site (4,716 kL ha(-1)). The average flow weighted mean (FWM) NO3-N concentration in tile drainage water over the 5-yr period was 11.8 mg N L(-1) for the NT site and 13.5 mg N L(-1) for the CT site. For both tillage systems, approximately 80% of tile drainage and NO3-N loss in tile drainage water occurred during the November to April non-growing season. Long-term NT improved wet aggregate stability, increased near-surface hydraulic conductivity and increased both the number and mass of earthworms relative to long-term CT. The greater tile drainage and NO3-N loss under NT were attributed to an increase in continuous soil macropores, as implied by greater hydraulic conductivity and greater numbers of earthworms.

Agriculture↗
PubMed2001

Water table management reduces tile nitrate loss in continuous corn and in a soybean-corn rotation.

Water table management systems can be designed to alleviate soil water excesses and deficits, as well as reduce nitrate leaching losses in tile discharge. With this in mind, a standard tile drainage (DR) system was compared over 8 years (1991 to 1999) to a controlled tile drainage/subirrigation (CDS) system on a low-slope (0.05 to 0.1%) Brookston clay loam soil (Typic Argiaquoll) in southwestern Ontario, Canada. In the CDS system, tile discharge was controlled to prevent excessive drainage, and water was pumped back up the tile lines (subirrigation) to replenish the crop root zone during water deficit periods. In the first phase of the study (1991 to 1994), continuous corn (Zea mays, L.) was grown with annual nitrogen (N) fertilizer inputs as per local soil test recommendations. In the second phase (1995 to 1999), a soybean (Glycine max L., Merr.)-corn rotation was used with N fertilizer added only during the two corn years. In Phase 1 when continuous corn was grown, CDS reduced total tile discharge by 26% and total nitrate loss in tile discharge by 55%, compared to DR. In addition, the 4-year flow weighted mean (FWM) nitrate concentration in tile discharge exceeded the Canadian drinking water guideline (10 mg N l(-1)) under DR (11.4 mg N l(-1)), but not under CDS (7.0 mg N l(-1)). In Phase 2 during the soybean-corn rotation, CDS reduced total tile discharge by 38% and total nitrate loss in tile discharge by 66%, relative to DR. The 4-year FWM nitrate concentration during Phase 2 in tile discharge was below the drinking water guideline for both DR (7.3 mg N l(-1)) and CDS (4.0 mg N l(-1)). During both phases of the experiment, the CDS treatment caused only minor increases in nitrate loss in surface runoff relative to DR. Hence CDS decreased FWM nitrate concentrations, total drainage water loss, and total nitrate loss in tile discharge relative to DR. In addition, soybean-corn rotation reduced FWM nitrate concentrations and total nitrate loss in tile discharge relative to continuous corn. CDS and crop rotations with reduced N fertilizer inputs can thus improve the quality of tile discharge water substantially.

Agriculture↗
PubMed1989

Diurnal variation in norepinephrine-stimulated release of pineal serotonin in vitro.

Adult, male rats were maintained under 12L:12D with lights on at 06.00h. Their pineal glands were incubated at 37 degrees C in the presence or absence of 10(-4)M norepinephrine (NE). 5-HT and various metabolites were quantitated in post-incubation media and pineal glands by high performance liquid chromatography coupled with electrochemical detection. No differences were observed in the quantities of 5-HT released by pineal glands in four hour incubations starting at either 06.00, 13.00 or 18.00 h; however, a highly significant decrease below these levels was observed at 01.00h. NE significantly stimulated 5-HT release at 13.00 and 18.00 h, but was ineffective at 01.00 and 06.00h. These results confirm recently reported stimulatory effects of NE on the release of 5-HT into pineal gland incubation medium and further suggest a diurnal rhythm of pineal gland sensitivity to NE in vitro with maximum stimulation of 5-HT release at midphotophase.

Animals↗
PubMed1982

Chiasmal optic neuritis.

Two patients exhibiting bitemporal hemianopia due to chiasmal optic neuritis with pathological confirmation of noncompressive lesions are presented; the first due to a chronic, idiopathic demyelinating process, and the second a result of ethchlorvynol (Placidyl) toxicity. The literature regarding chiasmal optic neuritis is reviewed, and a discussion of other noncompressive causes of bitemporal hemianopia is presented.

Adult↗
PubMed1976

A minicomputer-automated array spectrometer for liquid-chromatographic detection of metabolites.

A third-generation multiwavelength array spectrometer was developed as a detector for the high-resolution liquid-chromatographic characterization of metabolites. Components include a PDP-8/e minicomputer, matched pair of linear photodiode arrays, holographically-ruled gratings, fiber optics, flow cells, and high intensity xenon light source. The wavelength range is 256 nm differential with 1-nm resolution and can be adjusted from 200 to 800 nm. The system is capable of storing 20 spectra per second (200-456 nm) in a dual-beam mode. Special features include minicomputer-driven signal enhancement via integration as a function of signal strength. The display output includes presentation of the total absorption chromatogram vs. elution time in both real and post-run time as well as selectable single absorption band vs. elution time (post-run time). Application of this dedicated system is illustrated by the separation and charcterization of the metabolites of a carcinogen, 4-ethylsulfonyl-1 napthalenesulfonamide.

Animals↗
PubMedDate not supplied

Runoff and drainage losses of atrazine, metribuzin, and metolachlor in three water management systems.

Rainfall can transport herbicides from agricultural land to surface waters, where they become an environmental concern. Tile drainage can benefit crop production by removing excess soil water but tile drainage may also aggravate herbicide and nutrient movement into surface waters. Water management of tile drains after planting may reduce tile drainage and thereby reduce herbicide losses to surface water. To test this hypothesis we calculated the loss of three herbicides from a field with three water management systems: free drainage (D), controlled drainage (CD), and controlled drainage with subsurface irrigation (CDS). The effect of water management systems on the dissipation of atrazine (6-chloro-N2-ethyl-N4-isopropyl-1,3,5-triazine-2,4-diamine), metribuzin [4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4-triazine-5(4H)-one), and metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide] in soil was also monitored. Less herbicide was lost by surface runoff from the D and CD treatments than from CDS. The CDS treatment increased surface runoff, which transported more herbicide than that from D or CD treatments. In one year, the time for metribuzin residue to dissipate to half its initial value was shorter for CDS (33 d) than for D (43 d) and CD (46 d). The half-life of atrazine and metolachlor were not affected by water management. Controlled drainage with subsurface irrigation may increase herbicide loss through increased surface runoff when excessive rain is received soon after herbicide application. However, increasing soil water content in CDS may decrease herbicide persistence, resulting in less residual herbicide available for aqueous transport.

Acetamides↗