Brief Summary of Minutes of Annual Meeting

Cooperating Agencies and Principal Leaders:

W. Asbil* - Kemptville College, Univ. of Guelph

R. Ashley* - Univ. of Connecticut

R. R. Bellinder* - Cornell Univ.

C. E. Beste* - Univ. of Maryland

J. Cardina* - Ohio State Univ.

N. Creamer* - North Carolina State Univ.

A. DiTommaso* - Cornell Univ.

D. Doohan* - Ohio State Univ.

E. Gallandt* - Univ. of Maine

P. Johnston-Berresford* - Kemptville College, Univ. of Guelph

C. L. Mohler* - Cornell Univ.

J. R. Teasdale* - USDA-ARS Beltsville

Progress of the Work and Principal Accomplishments:

The year was a transition year between the old NE-92 project and the new NE-1000 project. Research continuing over from the NE-92 project is reported first. Rye variety trials begun under NE-92 are reported under NE-1000 since they meet objective 3 of the NE-1000 Project Outline and will continue under NE-1000.

NE-92 objective 1, Cover crop management and objective 2, Cultivation.
Combining cultivation and interseeded cover crops for weed control in transplanted cabbage, broccoli and tomato.

Cabbage (NY): Cabbage was cultivated 10, 20, and 30 days after transplanting (DAT) and interseeded either at the second or third cultivation with hairy vetch or oat. Vetch was regulated with a low rate of clopyralid and oats with sethoxydim at the point when the cover crops reached the same height as the crop. Regulation was compared to non-regulation, handweeding, a chemical standard and a weedy check. Results indicated that with regulation, both vetch and oats could be seeded 20 DAT without yield reduction in cabbage. Unlike some previous trials, in 2000 unregulated vetch seeded 20 DAT significantly reduced yield. Oat needed regulation when seeded at both times to avoid yield reductions. Weed biomass was reduced 85 and 94% for both cover crops seeded at 20 and 30 DAT, respectively. Weed biomass suppression with cultivation alone 30 DAT (3x) was equivalent to that provided by the cover crops but when cultivated only 2 times, weed suppression by the cover crops was 22% greater.

Fall-planted Broccoli (NY): This experiment was repeated in 2000 and will be done again in 2001. Broccoli was cultivated 0, 1, or 2 times at 10 day intervals, with or without rye inter-seeded at the final cultivation. Weedy, weed-free, and a chemical standard were included. A single cultivation 10 DAT was necessary and sufficient to avoid significant broccoli yield loss. Rye did not suppress yield when seeded at 10 DAT but did suppress yield when seeded at transplanting. When seeded 20 DAT rye did not establish well. Although pigweed (Amaranthus spp.) and hairy galinsoga (Galinsoga ciliata) that escaped cultivation did not suppress yield, they set seed prior to broccoli harvest.

Tomato (MD): Lana woolypod vetch was seeded at three rates and purple vetch at two rates before or after cultivation 17 DAT processing tomato. Seeding before cultivation resulted in greater vetch biomass, but biomass was unaffected by seeding rate. Woolypod vetch produced significantly more biomass than purple vetch. When seeded before cultivation, woolypod vetch plus uncontrolled weeds reduced yield; other vetch treatments did not reduce yield. Vetch appeared to suppress weeds, but not significantly.

NE-92 objective 3. Modeling and weed biology relevant to model paramaterization.
Relation of seed size to emergence through rye residue

An experiment was run in NY to test the ability of crop and weed species with different seed sizes to emerge through dead rye residue. Five weed species and 11 crop species ranging in seed weight from 0.5 to 414 mg were planted in small field plots and covered with 0, 0.25, 0.5, 1, 2 or 4 kg m2 of rye straw. For this year, as in previous years, the rate of decline in emergence with increasing mulch was a power function of seed mass.

NE-1000 objective 1. Mechanical weed management in high residue.

Rye was planted for this experiment in ME, NC, NY, OH, and ARS Beltsville.

NE-1000 objective 3. Cover crop variety trials.

Subterranean clover

ARS Beltsville evaluated 451 accessions of subterranean clover at two sites in MD for vigor, winter hardiness and density of leaves and stems. Due to the mild winter (1999-2000) most varieties survived until spring. The best performing accessions were planted again in September 2000.

Rye

Commercially available cultivars of rye (nine in NC and 8 in NY) were evaluated for their ability to suppress weeds. The rye was planted in the fall of 1999 and biomass production, allelopathic activity, and weed suppression in the field were assessed in summer 2000.

Unlike the 1999 results from NC but similar to 1999 results from NY, the varieties showed no difference in weed suppression in the field. Wrens 96 and Wrens Abruzzi produced most biomass in NC, whereas Aroostook was the most productive in NY and Wrens Abruzzi performed poorly.

An extract bioassay (NC) and a straw bioassay (NY) both showed Wheeler as having the highest allelopathic activity. In both cases, only certain test species were affected. Concentrations of DIBOA, an important rye allelotoxin, were assessed in the NC experiment. By flowering, DIBOA concentrations were low in all varieties, indicating that allelopathy demonstrated in the bioassay was due to some other compound(s).

Eleven commercial varieties were planted at MD, NC, NY, and ON in fall 2000 for evaluation in 2001. In addition, 280 rye accessions from the National Small Grains Collection were planted at NC. The best of these will be used to initiate a breeding program for cover crop rye.

NE-1000 objective 4. Weed management in crop rotation.

A faming systems trial at ARS-Beltsville initiated in 1996 continued to compare weed seedbanks, weed density and biomass in two, three and four year rotations with organic weed management. A long-term trial focused on potato in ME was modified to compare two and four year crop rotations each with and without soil amendment (cover crop green manure plus manure). Organic amendments increased potato yield 27% in 2000. Mechanical weed control was highly effective.

Usefulness of Findings

Inter-seeding trials will allow development of recommendations on best species, timing and methods for using inter-seeded cover crops to suppress weeds and improve soil in vegetable cropping systems.

Results from the experiment relating seed size to emergence through rye residue will allow extension of the model reported in Teasdale and Mohler (2000) (see publications). This will generalize growers ability to predict the degree of weed suppression that can be expected from a given amount of mulch.

Results from the rye variety trial will allow recommendations of best adapted varieties for use as weed suppressive mulch in various climatic zones within the region.

Results from the subterranean clover trials are expected to extend the range for this highly weed-suppressive cover crop into colder climatic zones.

The crop rotation experiments will allow recommendations on optimal crop sequences for maximum crop production and improved weed suppression with reduced herbicide inputs.

Work planned for next year

Work will proceed as specified in the Project Outline except for objective 1. For all objectives, additional locations will initiate work as indicated in the Project Outline.

The experiment for objective 1, Mechanical management in high residue has been modified. Rye will be killed by mowing at heading to prevent regrowth and enable movement of the residue into the crop row. Tillage treatments will contrast chisel/disk vs. zone tillage. Movement treatments within zone-till will be: (a) residue not moved; (b) residue moved into the crop row at planting; (c) residue moved at 2 leaf corn or 1st trifoliate soybean; (d) residue moved at 4 leaf corn or 3rd trifoliate soybean or layby. These treatments will be split to compare in-row residue effects where the in-row weeds are removed prior to residue movement vs. in-row weeds not removed but buried by the residue. All treatments will receive inter-row cultivation.

• Publications Issued or Manuscripts Approved During the Year:


Refereed Journal Articles (in print): 2

Proceedings Abstracts (in print): 3

• 
  Refereed Journal Articles:



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.


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:


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).


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).


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).