Brief Summary of Minutes of Annual Meeting

Objective 1. Mechanical weed management in high residue.
In Maryland, an experiment was conducted in a field with two cover crop treatments, rye planted at 90 lb/A and rye plus crimson clover planted at 60 + 20 lb/A. Before planting soybeans, cover crops in a portion of this field were bailed and removed from the field. Soybeans were planted into the bailed areas or into the standing cover crops on May 22. On the same day, cover crops were flail mowed or rolled. The following treatments were established in the flail mowed area: 1) no rye movement, 2) rye moved into the row on the same day as, but after planting, 3) rye moved into the row on June 18 when soybeans were tall enough to remain uncovered, 4) rye moved out of the row on the same day as, but after planting, and 5) rye moved out of the row on the same day as planting and into the row on June 18. Plots were cultivated with a Buffalo high residue cultivator. Soybean stand was higher in rye than in rye plus crimson clover (246,000 versus 157,000 plants/ha). Stand was higher in the bailed than in the flail mowed and rolled treatments (281,000 versus 143,000 and 180,000 plants/ha, respectively). In both cases, higher stand reductions were associated with higher residue biomass levels. Weed cover within row was inversely correlated with soybean stand. Normally, higher residue levels would be expected to reduce weed emergence and growth but in this experiment the opposite occurred suggesting that the competitiveness of the soybean canopy was more important than the mass of cover crop residue in suppressing weeds.

Mulch movement treatments 1 through 5 were all planted into similar residue levels followed by flail mowing so soybean stand was not an issue for comparison of these treatments. Weed cover in the row was lower in treatments 2 and 3 where mulch was moved into the row than in treatments 1, 4, and 5. However, weeds (primarily annual grasses) eventually developed to unacceptable levels in all plots by August. These results suggest that mulch movement can reduce weed pressure within the row. However, it is imperative that good crop stands become established since a competitive crop is apparently essential for this system to provide effective full season weed control.

In New York, Rye was planted in the fall of 2001 for a complimentary experiment, but extremely wet weather prevented tillage until early June. At that time the soil moisture was highly heterogeneous and the prospective planting date was extraordinarily late. Consequently, the experiment was cancelled since it was unlikely to provide meaningful data. ?Aroostook? rye was planted on 9/26/02 at 111 lb/a with 100 lb/a of 15-15-15 fertilizer for a repeat of the 2001 experiment in 2003.

Objective 2. Effects of mulch on soil moisture and weed emergence.
Cover crop residues may affect weed establishment through changes in soil temperature and available soil water. In New York, trials evaluating the germination of seeds of barnyardgrass, giant foxtail, and velvetleaf in solutions of various osmotic potential were carried out. A significant (P < 0.05) species by osmotic pressure interaction was found. For the 3 trials combined, germination of velvetleaf was inhibited by moisture potentials below ?30 kPa whereas giant foxtail germination peaked at -100 kPa and then decreased steadily, especially at moisture potentials above ?300 kPa. The germination of barnyardgrass seeds appeared least negatively affected by increasing osmotic potential. Highest germination levels for this species peaked at the -300 kPa level with a surprising 40% of seeds germinating at the -1000 kPa level. By contrast, no velvetleaf seeds and only 3% of giant foxtail seeds germinated under these extremely dry conditions. The rate of germination was delayed by decreasing moisture potentials for all species. Technical difficulties related to the establishment of appropriate soil moisture potential levels in pots have delayed the start of trials assessing the effect of soil moisture potential on weed emergence in sealed pots.

Objective 3. Cover crop variety trials.
Subterranean clover
Subterranean clover germplasm evaluations have identified very few lines that exhibit winter hardiness or vigor equivalent to or better than the current standard, Mt. Barker.
Rye
Maine. Eight rye varieties were tested at Stillwater, Maine, for winter survival, biomass production and weed suppression. All the varieties overwintered. Biomass production was consistently in the 4,000-5,000 kg/ha range except for ‘Maton‘ which produced an average of 6, 340 kg/ha. Weed suppression was fairly uniform amongst the plots, probably due to low weed pressure and droughty conditions. A wider testing of rye genetic material was planted in Orono in September of 2002. A total of 268 rye accessions from the National Small Grains Collection were planted to look at winter survival, heading date, and production of the allelochemical DIBOA (2,4-dihydroxy-1,4-(2H)benzoxazine-3-one). DIBOA will be quantified 3 times during the spring for all accessions using an experimental colorimetric technique adapted from wheat breeding programs.

Maryland. On October 30, 2001, nine rye varieties were drilled in 19 cm row widths with four replications. Glyphosate, 1.7 kg/ha was applied on May 6 and rye was sickle bar mowed on May 20, 2002. Rye plant population was moderately influenced by seed size probably due to variable germination; however, erratic seed viability appeared to have a greater influence on plant population than seed size. ?Wrens Abruzzi? had the greatest biomass of 3,900 kg/ha dry weight, but not significantly different from the varieties listed in descending order of biomass as follows: ?Wrens 96?, ?Early Grazer? and ?Elbon?. The biomass of other varieties in descending rank were as follows: ?Wheeler?, ?Oklon?, ?Maton?, ?Aroostook? and ?variety not specified?. All rye varieties, except ?variety not specified?, significantly reduced weed growth and ?Wrens Abruzzi?, ?Wrens 96?, ?Wheeler? and ?Oklon? provided the best weed control. Nitrogen fertilizer reduced weed suppression by rye straw biomass. Significant differences of anthesis over a 3 week period between rye varieties indicated varieties could be selected for specific spring periods for mechanical control after flowering.

New York. A trial comparing 8 varieties of rye and a bare control treatment was repeated for a fourth year. Varieties differed greatly in density in late fall, with Maton, Aroostook, Elbon and Wheeler establishing well but Wrens 96 and Wrens Abruzzi establishing poorly. Aroostook, the most northerly adapted variety, produced about twice the biomass of Wrens 96 by May 25, but otherwise biomass production among varieties did not differ significantly. Powell amaranth (Amaranthus powellii) and dandelion (Taraxacum officinale) were the major weeds this year. Neither of these species, nor total weeds, showed any response to rye variety this year.

Objective 4. Weed management in crop rotation.
In Ohio, the effect of three intensities of weed management was evaluated in the second year of a 4-year rotation study involving red clover, field corn, soybean and sweet corn. Mechanical weed control (hand hoeing) provided better control of annual grasses than did low- and high-rate herbicide programs. Full rate herbicides did not improve annual grass control over that obtained with low rate, and in the case of field corn, decreased grass control. Due to severe drought sweet corn was not harvested. Yield of soybean and field corn were low but unaffected by weed management system. Although weed communities were clearly affected by management, in no instance was weed control with herbicides improved when high-rate programs were used, relative to control obtained with low-rate herbicides.

Also in Ohio, a field experiment was established to 1) determine if No-seed Threshold (NST) and Critical Period of Competition (CP) were cost effective approaches to weed management during transition to organic and following certification; 2) to investigate the effects of NST and CP on crop performance during transition; and 3) to estimate the viable weed seed remaining in the weed seed bank each year. The field experiment was a 3-year rotation of winter wheat, oat/red clover, tomato, and cabbage. In 2001 and 2002, a total of 24 main plots and 48 subplots of cabbage and processing tomato were established. The total time taken to hoe/weed both NST and CP plots in cabbage and tomato crops during 2001 and 2002 was 20 h and 14 h, respectively. The additional hours taken to hoe/weed NST plots for each crop were 13 and 4 h for tomato, whereas those in cabbage were 12 and 3 in 2001 and 2002, respectively.

In Maine, a three-acre systems comparison was established in the spring of 2001. In four contrasting systems, this 4-year project will determine the annual and long term effects of contrasting 2- and 4-year cover crop based vegetable rotations on weed population dynamics, selected soil quality parameters, and crop yield, quality, and system profitability. To determine whether these cover-cropping practices affect resident invertebrate seed predators, we characterized the activity-density of seed predators by pitfall trapping over a 72 h period. There was greater density-activity of Harpalus rufipes in vegetated plots compared to those recently tilled and planted to a fall cover crop of oat (e.g., compare None, tilled to Winter Squash and Red clover). To measure seed predation, 25 seeds of each of six weed species were placed in the field. Seed recovery after 10 days in the field was 89% with vertebrate + invertebrate exclosures, intermediate at 55% with the vertebrate exclosures, and least at 43% with no exclosure (P < 0.001).

Weed dynamics continue to be followed in the Maine Potato Ecosystem Project. In 2002 density of germinable seeds, and thus potential weed pressure, was greater following soybean (10,218 germinable weed seeds per sq. m to 10 cm depth) than following each of the other crops in the rotation (Contrast P < 0.001; potato, 2863; barley, 4503; or forage, 2578 per sq. m. Weed control in potato was excellent across the pest management systems and was unaffected by soil management (grand mean 0.6 g per sq. m; median 0.0 g per sq. m).

In New York, crop rotation research was sited on new land purchased by the University from a neighboring farmer. The site had been in continuous alfalfa for five years. Prior to planting, the plots were marked out and soil samples taken for characterization, weed seed germination, and elutriation. Sweet corn was subsequently planted in all plots and three different levels of weed control were initiated: 0 chemical control, 0.33X (1X rate applied to a 10 inch band), and 1X herbicide rates. Plots receiving no herbicides were cultivated four times, beginning with a broadcast flex-tine weeder, followed by a Buddingh in-row finger weeder, and then a between-row S-tine cultivator (twice). Plots receiving the 0.5X banded herbicide rates were cultivated twice with the S-tine cultivator. The broadcast 1X treatments did not require cultivation in 2002. Field counts and soil germination results both identified 12 species and 8 of these were found with both methods. The elutriation technique identified 19 species, all of which were found by both of the other two methods. Species not seen in field counts and germination tests were most frequently winter annuals. The germination soil samples were frozen and have just recently been returned to the greenhouse for an additional germination period. The most frequent species in the trial as a whole were, in order of magnitude, galinsoga, redroot pigweed, and common lambsquarters. Galinsoga was by far, the most numerous but counts ranged from 2 to 5 in OX treatments in Rep 1 to 85 to 400+ in the same treatments in Rep IV.

Complete Listing of NE-1000 Publications

Refereed Journal Articles (in print): 15
Proceedings Abstracts (in print): 8
Theses: 1

Refereed Journal Articles:
1. Bellinder, R. R., J. J. Kirkwyland, R. W. Wallace, and J. B. Colquhoun. 2000. Weed control and potato (Solanum tuberosum) yield with banded herbicides and cultivation. Weed Technology 14:30-35.

2. Brainard, D.C. and R.R. Bellinder. 2001. Effect of cultivation and interseeded cover crops on weed suppression and cover crop establishment in transplanted kale and broccoli. Brighton Crop Prot. Conf. (Weeds) 2001 1:321-324.

3. Caldwell, B. and C.L. Mohler. 2001. Stale seedbed practices for vegetable production. HortScience 36:703-705.

4. Conklin, A.E., M.S. Erich, M. Liebman, D. Lambert, E.R. Gallandt, and W.A. Halteman (2002). Effects of red clover (Trifolium pratense) green manure and compost soil amendments on wild mustard (Brassica kaber) growth and incidence of disease. Plant and Soil 238:245-256.

5. Liebman, M. and E.R. Gallandt (2002). Differential responses to red clover residue and ammonium nitrate by common bean and wild mustard. Weed Science 50:521-529.

6. Liebman, M., and C.L. Mohler. 2001. Weeds and the soil environment. Pp. 210-268, in, Ecological Management of Agricultural Weeds, M. Liebman, C.L. Mohler and C. Staver. Cambridge University Press, Cambridge.

7. Liebman, M., C.L. Mohler and C. Staver. 2001. Ecological Management of Agricultural Weeds, M. Liebman, C.L. Mohler and C. Staver. Cambridge University Press, Cambridge.

8. Mohler, C. L. 2002. Mechanical weed control in agriculture. Encyclopedia of Pest Management, Supplement 2., David Pimentel, ed. Marcel Dekker: New York. Electronic publication at www.dekker.com.

9. Mohler, C.L. 2001. Enhancing the competitive ability of crops. Pp. 269-231, in, Ecological Management of Agricultural Weeds, M. Liebman, C.L. Mohler and C. Staver. Cambridge University Press, Cambridge.

10. Mohler, C.L. 2001. Mechanical management of weeds. Pp. 139-209, in, Ecological Management of Agricultural Weeds, M. Liebman, C.L. Mohler and C. Staver. Cambridge University Press, Cambridge.

11. Mohler, C.L. 2001. Weed evolution and community structure. Pp. 444-493, in, Ecological Management of Agricultural Weeds, M. Liebman, C.L. Mohler and C. Staver. Cambridge University Press, Cambridge.

12. Mohler, C.L. 2001. Weed life history: Identifying vulnerabilities. Pp. 40-98, in, Ecological Management of Agricultural Weeds, M. Liebman, C.L. Mohler and C. Staver. Cambridge University Press, Cambridge.

13. Mohler, C.L., M. Liebman, and C. Staver 2001. Weed management: The broader context. Pp. 494-581, in, Ecological Management of Agricultural Weeds, M. Liebman, C.L. Mohler and C. Staver. Cambridge University Press, Cambridge.

14. Sawma, J. T. and C. L. Mohler. 2002. Evaluating seed viability by an unimbibed seed crush test in comparison with the tetrazolium test. Weed Technology 16:781-786.

15. Teasdale, J. R. and C. L. Mohler. 2000. The quantitative relationship between weed emergence and the physical properties of mulches. Weed Science 48:385-392.

Abstracts in Proceedings:
1. Gallandt, E.R. (2001) Controlling Problem Weeds with Cover Crops. New England Vegetable and Berry Growers Conference Proceedings.

2. Mohler, C. L. 2000. Seed size controls the ability of seedlings to emerge through rye mulch. WSSA Abstracts, 2000 Meeting of the Weed Science Society of America 40:98, (No. 235).

3. Mohler, C.L. and J.C. Frisch. 2001. Measurement and modeling of depth changes of weed seed surrogates during tillage. WSSA Abstracts, 2001 Meeting of the Weed Science Society of America 41:113-114 (No. 274).

4. Nurse, R.E. and A. DiTommaso. 2002. Influence of photoperiod on barnyardgrass seed germination and seedling vigor. Proceedings of the 56th Annual Meeting of the Northeastern Weed Science Society of America, 56:3.

5. Nurse, R.E. and A. DiTommaso. 2003. Influence of seed pretreatment with sodium hypochlorite on seed germination and radicle elongation in three annual weed species. Proceedings of the 57th Annual Meeting of the Northeastern Weed Science Society of America, 57:123.

6. Reberg-Horton, C., N. Creamer, J. Burton, N. Ranells, and C. Mohler. 2001. Bioassay and field evaluation of rye cultivars for allelopathy. WSSA Abstracts, 2001 Meeting of the Weed Science Society of America 41:109-110 (No. 274).

7. Reberg-Horton, C., N. G. Creamer and C. L. Mohler. 2000. The suppression of weeds by nine varieties of rye (Secale cereale). WSSA Abstracts, 2000 Meeting of the Weed Science Society of America 40:27-28, (No. 66).

8. Teasdale, J. R. and C. L. Mohler. 2000. The physical properties of mulches contributing to weed suppression. Third International Weed Science Congress, Foz do Iguassu, Brazil, June 6 to 11, 2000, Abstracts, pp. 95-96 (No. 204).

Thesis:
1. Brainard, D. C. 2002. Weed management implications of a broccoli-winter rye intercropping system. Ph.D. Dissertation, Cornell University Press, Ithaca, NY 14853, 136pp.