Flexible Tine Weeding for Summer Annual Weed Control in Small Grains
Berks County, 2004
Ron Hoover, On-Farm Research Coordinator
Mena Hautau, Berks County Extension Educator
Michele Gauger, PASA
Anne & Tim Bock, Wills Daal Farm
Weed control continues to be one of the greatest production challenges for producers of organic horticultural and agronomic crops. Growers often rely on combinations of cultural practices to manage their weed problems. Possibilities include crop rotation, cover cropping, mulching, early planting, delayed planting, or mechanical destruction of weeds after the crop is planted. Row cultivation of spaced-row crops is efficient in removing weeds from the interrow and can be used several times during a period of several weeks to control later emerging weeds. Rotary hoes and flexible tine weeders can be used soon after planting row crops or drilled crops that emerge slowly or develop tough seedlings. There is essentially no mechanical management of weeds after drilling of small grains. Some farmers have speculated that rotary hoes or flexible tine weeders might be capable of weed control with minimal damage to the small grain crop.
To compare summer annual weed populations and spring oat grain yields after single, double and triple cultivations with a flexible tine weeder. The idea of using a flexible tine weeder in small grain production stemmed from positive observations in other research trials. We were all interested if the number of tine weedings would decrease weed populations and increase oat yields.
- Tim & Anne Bock
- Kutztown, Berks County , Pennsylvania
- Soil type:
- Sandy loam
- Previous crop:
- Cattle manure on soybean stubble
- Seeding Rate:
- 4.5 bushels/acre
- Moldboard plow, field cultivator, flexible tine weeder
- Harvest date:
- July 31, 2004 (combine harvest of spring oats)
A field of approximately 3 acres in size was used, and was prepared after being in soybean in 2003, by moldboard plowing (April 8, 2004) and field cultivation (April 15, 2004). Spring oats, “Blaze” variety were drilled on April 16, 2004.
A total of three treatments with a Lely 15’ flexible tine weeder were used. Each treatment plot, measuring 15’ wide by 560 to 620’ long, had either one, two or three weeding treatments with the tine weeder (see Table 1). The weeding treatments were replicated four times within a randomized complete block design.
Tim Bock tine weeding five days after drilling oats before oat emergence.
Table 1. Dates of tine weeding treatments.
|Tine Weeding Treatment|
|1 time||2 times||3 times|
|Date of Weeding|
|April 19||Apriil 19||April 19|
|April 25||April 25|
Flexible tine weeders are designed to disturb the root zones of weed seedlings while they are in the very delicate “white thread root” stage, which often results in seedling dessication and death. The weeder ran approximately 5-6 mph.
First treatment – April 19, prior to oat emergence – weeder penetrated about 1” below the surface. This depth was decreased slightly on April 25 during the second weeding, the third treatment on April 30.
Damage to the oats during the second and third cultivations did increase as the oats grew in height. Very few weeds were beginning to germinate during the weedings. There was significant visual damage to the oats, which were 3 to 4 inches tall.
On May 25, a survey of summer annual weed and spring oat densities were conducted. Six sample quadrats were counted per treatment plot.
On July 28, aboveground biomass was clipped from three quadrats per treatment plot. These clippings were separated into weed and oat fractions. Samples were then dried and weighed to determine aboveground biomass yields.
The spring oats were combined harvested on July 31. A center of 13’ of each plot was harvested and weighed determined by transferring grain into a farm gravity bin resting on large-capacity electronic wheel weighers. Grain moisture levels were also collected (corrected to yield 13%).
Comparison of oats tine weeded three times (left) to oats weeded twice. Picture taken immediately after third tine weeding. In spite of oats being covered with soil during the third weeding, grain yields between treatments were not different at harvest.
The spring and summer of 2004 were much wetter than average. Tillage operations produced soil crumbs and clods and planting was delayed by three weeks. The tine weedings were conducted on soil that was slightly wetter than optimal, and although the weeder was adjusted to operate at shallow depths, additional clods were brought to the surface. The soil surface was not ideal for weeder disruption of the weed seed germination zone.
There were no differences between treatments for density of the predominant weeds or the oats when surveyed on May 25 (see Table 2). Likewise, when total plant biomass was sampled at oat maturity and separated into weed fractions and oats, no differences were observed for weeding frequency treatments (see Table 3) or for grain yields collected with the combine at final harvest (see Table 4).
Separations of grass and broadleaf weeds from oats prior to harvest
|Giant foxtail||Common ragweed||PA smartweed||VA copperleaf||Spring Oats|
|plants per square meter|
|One Weeding||Two Weedings||Three Weedings|
|weed dry matter (grams/square meter)|
|One weeding||Two weedings||Three weedings|
|oat yield bushels/acre|
Expectations were that additional flexible tine weedings would result in less weedy, higher yielding oats. This was not the result. Although a “non-weeded” treatment was not included, visual comparisons with adjacent non-weeded parts of field indicated similar weed species and densities. The greatest reason for lack of control of weeds in this experiment was the species present in this weed seedbank normally germinate later than when spring oats are planted and the tine weedings occurred. Further, it should be noted that for tine weeding to be effective, a fine soil surface (smaller soil particles) would permit the tines to disturb a greater percentage of the surface soil. This should result in better control of weed seedlings than would be possible when large soil crumbs or clods exist. These large structures, left intact after weeding, will “protect” weed seedling roots from the desiccation that results when the soil/root interface is disturbed.
Fall-planted winter small grains may be better suited to utilize flexible tine weeding for weed control. The winter annual weeds most often cited as problems in these crops (mustards, chickweeds, henbit, etc.) often germinate during the time when farmers are planting the crop. More closely matching crop planting and weed germination should enable farmers to use weeders for management of some of these weeds. This concept should be tested on these crops.
Although weed control benefits were not demonstrated in this, a surprising outcome was that grain yields were not negatively impacted by later tine weedings when oat shoot lengths were approaching 4 inches. Many clods were rolled onto shoots, but the oats were able to compensate and yield as well as those plots weeded only once, prior to oat emergence.
For a future investigation, we are considering fall-planted winter small grains, which may be better suited to benefit from the flexible tine weeder. Winter annual weeds (mustards, chickweed, henbit, etc.) germinate during the time when farmers are planting the crop. More closely matching schedules of crop planting and weed germination should enable farmers to use weeders for management of some of weed species.