Influence of Tillage and Herbicides in Onion Field Data Year 2

Transcription

1 Influence of Tillage and Herbicides in Onion Field Data Year 2 Sarah Gegner, Harlene Hatterman-Valenti, Walt Albus, Collin Auwarter North Dakota State University and Oakes Research Extension Center Objectives The main objective for this research is to evaluate the potential for strip tillage in onion production and to understand the influence of strip tillage on factors such as weed seed germination, soil moisture content, soil temperature, and erosion control. In addition, the effect of strip tillage on herbicide efficacy in onion prior to the two-leaf growth stage will be evaluated. Materials and Methods A field experiment was conducted at the North Dakota State University Research Extension Center near Oakes, North Dakota, on an Embden loam soil. The experiment was set up as a stripblock with four replicates. The main plot consisted of a tillage system (strip tillage or conventional tillage); the sub-plots consisted of herbicide treatments. The strips were made in the fall of 2007 (November 20) and again in the spring (April 23, 2008) using a shank type unit; the conventional tillage treatment was Roto-tilled twice in the fall and again on April 23, Onion variety Teton seed (TE) was planted April 23 in double rows at a rate of 285,000 seeds per acre. Plots were 6 feet wide and 17 feet long with 4-foot alleys between each replicate. Herbicides included DCPA (Dacthal), pendimethalin (Prowl H20), oxyfluorfen (Goaltender), and bromoxynil (Buctril). DCPA and pendimethalin were applied as pre-emergence herbicides on May 1; post-emergence applications with reduced rates of oxyfluorfen or bromoxynil (microrates) were made at four weekly intervals starting when annual broadleaf weeds reached the cotyledon to first true-leaf stage. The first application was made on May 16. Pre-emerge applications were applied at 10 lbs/acre and 1.5 pt/acre for DCPA and pendimethalin, respectively. Micro-rate applications were applied at 2 oz/acre and 4 oz/acre for oxyfluorfen and bromoxynil, respectively. The entire experiment received a post-emergence application of clethodim (Select) after the onions had reached the two-leaf growth stage and an application of dimethenamid-p (Outlook) when onions were at the five-leaf stage, to help minimize late-season weeds. Best management practices were used for fertility, irrigation, disease, and insect control throughout the entire experiment. Herbicide effectiveness was evaluated through weed counts using a square foot area in the center of each plot. Visual ratings were taken seven days after the fourth micro-rate application to also evaluate weed control. A scale of percent control was used, where 0 equaled no control and 100 equaled complete control. Annual broadleaf weeds of most concern were common lambsquarters, redroot pigweed, and hairy nightshade. Weed counts were taken seven days after each herbicide micro-rate application. Temperature and moisture probes were installed May 15 at a depth of 2 inches. The probes took temperature and moisture readings every 60 minutes throughout the season. Probes were installed in the row of the conventionally tilled plots and in the row as well as in the strip (between the row) of the strip-tilled plots.

2 Plots were hand harvested on September 24 and were allowed to dry until September 30. Onion bulbs were graded according to USDA standards into four classes: small (1-2 inches), medium (2-3 inches), large (3-4 inches), and colossal (4+ inches). Total marketable yield includes grades medium and large. Results Micro-rate herbicide applications made prior to the two-leaf growth stage did not injure onions during establishment (data not shown). Volumetric water content is highest between rows in the strip-tilled plots. This is due to the extra residue found within the inter-row area, which acts as an insulation above the soil, holding moisture in. Water content is lowest in the row of the striptilled plots. The conventional tilled volumetric water content of the soil is a little above the striptilled in row. See Graph 1. Temperature was coolest under the residue cover found in the inter-row area of the strip-tilled plots. A misconception of a strip-tilled system is that the soil does not warm up as fast as in a conventionally tilled system. However, Graph 2 proves that strip-tilled soil warms up just as much as conventionally tilled soil within the row/strip. Hairy nightshade was more of a problem in the plots treated with DCPA. Weed pressure was higher in the conventionally tilled plots than in the strip-tilled plots. See Graphs 3 and 4. Common lambsquarters was highest in the conventional oxyfluorfen plots. Overall, weeds were a little more prevalent in the strip-tilled plots vs. the conventionally tilled plots. See Graphs 5 and 6. There was little to no redroot pigweed pressure in all treatments (data not shown). Total marketable onion yield grade did vary between tillage system and herbicide but generally was only numerically higher with the strip tillage and herbicide treatment for the various onion grades. Noticeable exceptions occurred with onions graded between 1-2 inch diameters (grade small), where the conventional-tillage and herbicide treatment numerically yielded higher than its corresponding herbicide treatment in strip tillage. The yield grade kg/ha for each tillage and herbicide treatment are illustrated in Table 1. A cool, wet year is not favorable for a strip tillage system. However, the data shown here, illustrate that even in a cool, wet year strip tillage does not significantly decrease yield of onion compared to a conventionally tilled system.

3 Graph 1. Volumetric water content averaged across reps from May 26 to June 7. (Legend found in Graph 2). Graph 2. Temperature averaged across reps from May 26 to June 7.

4 Graph 3. Hairy Nightshade weed counts in strip tillage averaged across reps. Graph 4. Hairy Nightshade weed counts in conventional tlllage averaged across reps. Graph 5. Common lambsquarters weed counts in strip tillage averaged across reps.

5 Graph 6. Common lambsquarters weed counts in conventional tillage averaged across reps. Table 1. Effect of tillage and herbicide on onion grade/yield. Tillage Herbicide Grade: Small Grade: Med Onion yield: kg/ha Grade: Large Colossal Total Marketable Strip Prowl H20 4,664 20,918 26, ,881 Conv Prowl H20 8,100 20,451 23, ,365 Strip Dacthal 6,261 24,963 24, ,128 Conv Dacthal 7,795 24,317 25, ,684 Strip Goaltender 8,414 23,412 15, ,840 Conv Goaltender 10,073 20,532 7, ,390 Strip Buctril 7,723 21,609 21, ,092 Conv Buctril 10,145 22,174 21, ,791