Postplant tillage provides limited weed control in flax, lentil and hard red spring wheat (continued)

Keywords

Introduction

Materials and
Methods

Results and
Discussion

Conclusion/
Implications

Future Research
Needs

References

Related
www Sites

Project
Background

Herbicides can be used to control grass and broadleaf weeds in flax and lentil (Zollinger, 1997), but can be expensive. Herbicide rates have been reduced by integrating tillage with herbicide treatments in corn (Mulder and Doll, 1993) and soybean (Savage and Loux, 1992). Postplant tillage may represent a lower-cost alternative to herbicides in flax and lentil, as well as in other solid seeded crops like spring wheat. Our objective was to determine the efficacy of postplant spring tine harrowing, rotary hoeing and herbicide treatments for controlling weeds in flax, lentil and hard red spring wheat in an experiment conducted over two years.




Materials and Methods
The experiment was conducted under dryland conditions at the Dickinson Research Extension Center during 1994 and 1995 on Farnuf loam soil (fine-loamy, mixed Typic Argiboroll). The study was initiated in a field with a high indigenous population of green foxtail (Setaria viridis (L.) Beauv.), redroot pigweed (Amaranthus retroflexus L.) and common lambsquarters (Chenopodium album L.), along with smaller populations of other weed species in each year. Flax cultivar ‘CI 3131’, ‘Crimson’ lentil and ‘Stoa’ hard red spring wheat were each sown 1.25 inches deep in 6-inch row spacings using a 10-ft press drill (Deere & Co). Flax was seeded at 69 pure live seed (PLS)/ft² (40 lb/acre), lentil at 14 PLS/ft² (50 lb/acre), and wheat at 18 PLS/ft² (60 lb/acre).

Crops were seeded on 3 May 1994 and 12 May 1995. Weed control treatments imposed after seeding were: (i) rotary hoeing or (ii) spring tine harrowing once, each at 5 DAP; (iii) rotary hoeing or (iv) harrowing twice, each at 5 DAP and repeated when flax and lentil plants were approximately 6 inches tall and wheat plants had three to four leaves (approximately 28 DAP); (v) rotary hoeing or (vi) harrowing at 5 DAP and applying bromoxynil 2E (Rhone Poulenc) at 0.25 lb ai/acre in flax and wheat and metribuzin 75DF (Bayer) at 0.25 lb ai/acre in lentil at 28 DAP; (vii) applying sethoxydim 1.5E (BASF) at 0.5 lb ai/acre and bromoxynil at 0.25 lb ai/acre in flax, sethoxydim at 0.5 lb ai/acre and metribuzin at 0.25 lb ai/acre in lentil, and diclofop 3E (AgrEvo) at 0.9 lb ai/acre and 0.25 bromoxynil at 0.25 lb ai/acre in wheat at 28 DAP; and (viii) pulling weeds by hand. A no-weed-control check plot also was included.

A 6-ft rotary hoe with two wheels per spring-tensioned shank (Deere & Co.) was used down the middle of each plot for rotary hoe treatments; no data were collected from the area that was not rotary hoed. A 10-ft spring-tine harrow (Deere & Co.) with tines set back to minimize soil penetration was used for the harrow treatments. Rotary hoe and harrow speed was 7.5 mi/h. Herbicides were applied in 9 gal water/acre with a CO₂-pressurized bicycle sprayer with three 8001 flat-fan nozzles (Tee-Jet). Weed control treatments were randomized and applied perpendicular to the direction the crops were sown.

The experiment was a randomized complete block with plots in a split-plot arrangement and blocks replicated four times. Crops comprised the main plots and weed control treatments constituted subplots. Main plots were 10 by 90 ft wit subplots of 10 by 10 ft.

Crop plant populations were determined in two 5.4-ft² (0.5-m²) quadrats randomly placed within each plot on 1 June 1994 and 19 June 1995. Grass and broadleaf weeds and crop plants were harvested separately by hand from a 10.7-ft² (1-m²) quadrat in each plot for determination of above-ground dry matter production. Flax was harvested on 4 August 1994 and 14 August 1995. Lentil was harvested on 8 August 1994 and 9 August 1995. Wheat was harvested on 1 August 1994 and 10 August 1995. Crop and weed plant samples were dried at 140^oF for 48 to 72 h and a dry weight recorded. Then crop samples were threshed and seed yield determined.

Data within this experiment were analyzed using the ANOVA procedure available from SAS (SAS Inst., 1985). Crop and weed control treatments were considered fixed effects while years were considered random effects. Where F tests indicated significant differences (P < 0.05) among treatments, means were separated using Fischer=s protected LSD. Years were combined in the ANOVA. The appropriate error term from the combined analyses was used to test each environment-year when significant interactions existed between environment-year and crop or environment-year and weed control treatment. Similarly, the appropriate error term from the combined analyses was used to test each crop when a significant interaction existed between crop and weed control treatment.

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Table of Contents – Fall 1997