Solid-phase extraction: method development, sorbents, and coupling with liquid chromatography

Effect of water stress at different development stages on vegetative and reproductive growth of corn

http://www.nurserycropscience.info/water/managing-runoff/technical-pubs/reichenberger-et-al.-2007.-mitigation-strategies-to-reduce-pesticide-inputs-into-ground-and-surface-water-and-their-effectiveness-a-review

Mitigation strategies to reduce pesticide inputs into ground- and surface water and their effectiveness; A review

Environmental and health effects of the herbicide glyphosate.

Introduction to Soil Microbiology

Herbicides applied to soils potentially affect soil microbial activity. Quantity and frequency of glyphosate application have escalated with the advent of glyphosate-tolerant crops. The objective of this study was to determine the effect of increasing glyphosate application rate on soil microbial biomass and activity. The soil used was Weswood silt loam. The isopropylamine salt of glyphosate was added at rates of 47, 94, 140, and 234 µg ai g−1 soil based on an assumed 2-mm glyphosate–soil interaction depth. Glyphosate significantly stimulated soil microbial activity as measured by C and N mineralization but did not affect soil microbial biomass. Cumulative C mineralization, as well as mineralization rate, increased with increasing glyphosate rate. Strong linear relationships between mineralized C and N and the amount of C and N added as glyphosate (r2 = 0.995, 0.996) and slopes approximating one indicated that glyphosate was the direct cause of the enhanced microbial activity. An increase in C mi...

Effect of glyphosate on soil microbial activity and biomass

An understanding of the response of plants to water deficits is important in efforts to model cotton (Gossypium hirsutum L.) growth, estimate irrigation needs, and breed drought-resistant cultivars. This study examined shoot and root growth of a longand a short-season cotton cultivar after a brief drought and subsequent recovery period. Seeds were planted in fritted clay-filled pots in a growth room under fluorescent lights at about 27 (C. Plants were divided at 36 d after planting into drought-treatment and watered-control groups. Plants were sampled after a 13-d drought and again after a 10-d recovery period. There were no treatment-by-genotype interactions. At the end of the drought and recovery, height, leaf P.F. Pace, DEKALB Genetics Corporation, 3100 Sycamore Road, DeKalb, IL 60115; Harry T. Cralle, Department of Soil and Crop Sciences, Texas AM Sherif H. M. El-Halawany (deceased), Cotton Research Institute, Agricultural Research Center, Ministry of Agriculture, Giza, Egypt; J. Tom Cothren , Department of Soil and Crop Sciences, Texas AM Scott A. Senseman, Department of Soil and Crop Sciences, Texas AM Masle and Passioura, 1987). Several studies have shown that drought inhibits cotton canopy development. Krieg and Sung (1986) determined that drought decreases the number of leaves on sympodial branches of cotton. Leaf area of glasshouse-grown cotton also was inhibited when the percentage of soil-available water was less than 51 ± 15% (Rosenthal et al., 1987). Cutler and Rains (1977) concluded that predawn leaf water potentials below $0.5 MPa were accompanied by decreased leaf elongation rate. Leaf expansion of 55-d-old cotton plants slowed after 2 d of withholding water, which meant that leaf growth was more sensitive than root elongation to drought (Ball et al., 1994). Similarly, McMichael and Quisenberry (1991) found that terminal drought decreased the shoot:root ratio. Drought also reduced the growth, development, and distribution of cotton roots (Malik et al., 1979; Taylor, 1983). Root growth of 55-d-old cotton was reduced after 6 d of withholding water (Ball et al., 1994). The number of roots elongating decreased by 35% during the drought. Planting early-maturing cultivars can decrease the amount of water used by cotton, and other traits in future cotton cultivars may further decrease the amount of water used. Quisenberry et al. (1981) found considerable variability for heat tolerance, root growth, dry matter accumulation, and water use efficiency among exotic cotton strains under dryland conditions. Gerik and co-authors (1996) compared two short-season cotton cultivars and found that one, Tamcot HQ95, yielded more than other, GP74, regardless of the level of water stress. They concluded that the photosynthetic capacity of Tamcot HQ95 might be greater than that of GP74. Root elongation during drought may help plants get deeper water, thus avoiding water deficits near the soil surface. Elongation also could reduce the water lost by drainage when precipitation allows recovery after the drought (Ludlow and Muchow, 1990). If, however, water is unavailable deeper in the soil profile, longer roots may reduce shoot dry weight and harvest index by allowing the preferential partitioning of photosynthate to roots at the expense of shoots. This study examined various measures of shoot and root growth of one longand one short-season cotton cultivar after a drought of limited duration and a subsequent recovery period. MATERIALS AND METHODS A long-season cotton, ‘Stoneville 506,’, and a short-season cotton, ‘Tamcot HQ95,’ were planted in pots (9-L volume, 20 cm deep) filled with fritted clay (Absorb-N-Dry, Balcones Co., Flatonia, TX). Filter paper at the bottom of the pots retained the fritted clay while allowing for drainage. Two plants were seeded per pot and were supplied with distilled water every other day for 10 d. The pots were then watered with a nutrient solution of 0.90 g L of 2020-20 NPK fertilizer (Peters Professional All Purpose Plant Food, Spectrum Group, Division of United Industries Corp., St. Louis, MO) until 36 d after planting. This fertilizer was selected because soil tests showed that the fritted clay had very low levels of N, P, and K and that nutrients would be quickly leached from this well-drained soil. Water or nutrient solution, when applied, was added until an excess drained from the bottom of the pot. The experiment 185 JOURNAL OF COTTON SCIENCE, Volume 3, Issue 4, 1999 was conducted in a growth room under fluorescent lights providing a photosynthetic photon flux density of 700 )mol m s for 16 h d. Temperature was maintained at 127 (C. At 36 d after planting, plants were randomly divided into drought-treatment and watered-control groups. The drought-treated plants were not watered for 13 d. At the end of this drought treatment (49 d after planting), control and drought-treated plants were sampled and height, number of nodes, leaf area, and taproot length were measured. Secondary root length of fresh roots was measured by a Comair Root Length Scanner (Commonwealth Aircraft Corp. Ltd, Melbourne, Australia). Leaves, stems, and tap and secondary roots were dried for 48 h at 90 (C before dry weights were determined. The shoot:root weight ratio was calculated from the dry weights. At 49 d after planting, the remaining droughttreated plants were watered during a 10-d recovery period. At 59 d after planting, both treatments were sampled as described above. The experiment was a randomized complete block design with two blocks. Each block had four pots of each cultivar. Each pot had two plants. The experiment was repeated twice. There was no interaction between treatment and experimental run, so data from the two runs were pooled for statistical analysis. The cultivar primary effect was insignificant, so data also were pooled across cultivar. This analysis used the SAS System (SAS Institute, Cary, NC). RESULTS AND DISCUSSION At the end of the drought treatment, droughttreated plants had significantly (P < 0.05) lower height, less leaf area, fewer nodes, and lower dry weights of stems and leaves than did the controls (Table 1). Additionally, the drought-treated plants had a lower shoot:root ratio (Table 2) than did the controls at this sampling, 49 d after planting. There were no differences between the two treatments in the lengths of the secondary roots or in the dry weight of the secondary or taproots at the end of the drought period (Table 3). However, the droughttreated plants had a significantly (P < 0.01) greater tap root length than did the controls at this time (49 d after planting). The taproot dry weight in the drought-treated plants was identical to that of controls, so the drought-related elongation occurred at the expense of taproot thickening. While the drought-treated plants had a taproot dry weight per length of only 0.011 g cm, the corresponding measurement for the well-watered controls were Table 1. Heights and dry weights of stem, leaf area and dry weight, and node number in drought-treated and control plants of Stoneville 506 and Tamcot HQ95 at the end of the drought, 49 d after planting.† Means are followed by standard errors of the mean in parentheses.

https://intranet.cotton.org/journal/1999-03/4/upload/jcs03-183.pdf

Drought-induced Changes in Shoot and Root Growth of Young Cotton Plants

Although the effectiveness of vegetative filter strips (VFS) for reducing herbicide runoff is well documented, a comprehensive review of the literature does not exist. The objectives of this article are to denote the methods developed for evaluating herbicide retention in VFS; ascertain the efficacy of VFS regarding abating herbicide runoff; identify parameters that affect herbicide retention in VFS; review the environmental fate of herbicides retained by VFS; and identify future research needs. The retention of herbicide runoff by VFS has been evaluated in natural rainfall, simulated rainfall, and simulated run-on experiments. Parameters affecting herbicide retention in VFS include width of VFS, area ratio, species established in the VFS, time after establishment of the VFS, antecedent moisture content, nominal herbicide inflow concentration, and herbicide properties. Generally, subsequent transport of herbicides retained by VFS is reduced relative to adjacent cultivated soil because of enhanced sorption and degradation in the former.

https://bioone.org/journals/weed-science/volume-53/issue-3/WS-03-079R2/Reducing-herbicide-runoff-from-agricultural-fields-with-vegetative-filter-strips/10.1614/WS-03-079R2.pdf

Reducing herbicide runoff from agricultural fields with vegetative filter strips: a review

Herbicides applied to soils potentially affect soil microbial activity. The quantity and frequency of Roundup Ultra [RU; N-(phosphonomethyl)glycine; Monsanto, St. Louis, MO applications have escalated with the advent of Roundup-tolerant crops. The objective of this study was to determine the effect of Roundup Ultra on soil microbial biomass and activity across a range of soils varying in fertility. The isoproplyamine salt of glyphosate was applied in the form of RU at a rate of 234 mg active ingredient kg -1 soil based on an assumed 2-mm glyphosate-soil interaction depth. Roundup Ultra significantly stimulated soil microbial activity as measured by C and N mineralization, as well as soil microbial biomass. Cumulative C mineralization as well as mineralization rate increased above background levels for all soils tested with addition of RU. There were strong linear relationships between C and N mineralized, as well as between soil microbial C and N (r 2 = 0.96 and 0.95, respectively). The slopes of the relationships with RU addition approximated three. Since the isopropylamine salt of glyphosate has a C to N ratio of 3:1, the data strongly suggest that RU was the direct cause of the enhanced microbial activity. An increase in the C mineralization rate occurred the first day following RU addition and continued for 14 d. Roundup Ultra appeared to be rapidly degraded by soil microbes regardless of soil type or organic matter content, even at high application rates, without adversely affecting microbial activity.

Effect of roundup ultra on microbial activity and biomass from selected soils.

Background: Repeated applications may have a greater impact on the soil microbial community than a single application of glyphosate. Experiments were conducted to study the effect of one, two, three, four or five applications of glyphosate on soil microbial community composition and glyphosate mineralization and distribution of 14C residues in soil.



RESULTS: Fatty acid methyl esters (FAMEs) common to gram-negative bacteria were present in higher concentrations following five applications relative to one, two, three or four applications both 7 and 14 days after application (DAA). Additionally, sequencing of 16S rRNA bacterial genes indicated that the abundance of the gram-negative Burkholderia spp. was increased following the application of glyphosate. The cumulative percentage 14C mineralized 14 DAA was reduced when glyphosate was applied 4 or 5 times relative to the amount of 14C mineralized following one, two or three applications. Incorporation of 14C residues into soil microbial biomass was greater following five glyphosate applications than following the first application 3 and 7 DAA.



CONCLUSION: These studies suggest that the changes in the dissipation or distribution of glyphosate following repeated applications of glyphosate may be related to shifts in the soil microbial community composition. Copyright © 2009 Society of Chemical Industry

Scott A. Senseman

Papers

Effect of glyphosate on soil microbial activity and biomass

Drought-induced Changes in Shoot and Root Growth of Young Cotton Plants

Reducing herbicide runoff from agricultural fields with vegetative filter strips: a review

Effect of roundup ultra on microbial activity and biomass from selected soils.

Effects of repeated glyphosate applications on soil microbial community composition and the mineralization of glyphosate