| ||Conventional tillage methods are expensive, time consuming, increase the risk of soil erosion and dry out the soil when used to remove forage from a rotation.
Direct seeding of cereals, oilseeds and pulse crops into a herbicide killed forage crop has proven successful under research and field conditions.
In most cases, conventional tillage operations do not completely remove the forage crops, especially those with extensive root systems such as alfalfa and smooth bromegrass.
Conventional tillage operations used to remove forages from the rotation can reduce many of the accumulated soil improvement benefits associated with growing forages. The principles of establishing forage crops in a direct seeding program are the same as in a conventional seeding program. Stand establishment has been successful with direct seeding equipment when forages have been seeded into stubble with or without a cover crop.
The following are tips for the establishment and removal of forage crops in a direct seeding program based on research and farmer experience.
The extra time available for crop growth after directly seeding into a forage stand allows for a build up of nitrogen, the breakdown of sod, reducing soil borne disease organisms and a more suitable seedbed.
The success of spring spraying program may be limited due to cool weather conditions and lack of satisfactory growth of forages before herbicide application. Spring spraying does not allow sufficient time between spraying and seeding to allow for the breakdown of the old forage stand and preparation of a good seed bed.
Research work at the Agriculture and Agri-Food Canada, Brandon Research Station indicates that Roundup® effectiveness may be reduced when air temperatures are below 15 degrees C. This is especially true at application rates below 1 litre/acre. As application rates increase, the effect of temperature decreases.
When using glyphosate products, grasses should have at least 3-4 leaves per stem and legumes should be in the bud or blooming stage. If legumes have not reached the bud stage, 2-4,D or Banvel products should be considered for effective control of legumes. Please follow label recommendations and ensure the products are registered for tank mixing.
Rates of 1 ½ to 2 litres/acre of glyphosate products are recommended to remove forage stands in a direct seeding program.
To date our best results have been using Roundup® as a preharvest treatment on hay or pasture aftermath production that has not been cut or grazed since mid-July and sprayed in early September at the 1½ litre rate.
Some risk occurs when waiting to spray in late August or early September. Dry weather can slow the regrowth of forages - especially grasses - thus limiting the effectiveness of glyphosate products. Wait for plants to recover if more than 3 or 4 degrees C of frost occurs.
Soil borne disease organisms occurring from the breakdown of heavy sod can affect the establishment and growth of some crops, particularly barley and newly seeded forages. This is especially true in spring spraying programs. Generally oats and wheat should be considered before barley or peas when seeding into herbicide treated sod. However, there has been successful establishment of barley, canola and pea crops when seeded into forage stands that have been spring sprayed or sprayed the previous year. The longer the period of time between spraying and seeding the less chance of soil borne diseases affecting the newly seeded crop.
New crop choice should also be considered for when selecting the herbicide. Alfalfa regrowth can be controlled with cheaper herbicides for subsequent cereal production than for subsequent canola production.
Roundup® is the only glyphosate product registered as a preharvest treatment for the termination of forage crops from the rotation. Preharvest treatments should be applied three to seven days before the expected cutting or grazing date. Please allow at least three days after spraying before cutting or grazing. Time must be given to allow the herbicide to translocate into the root system.
A slight decrease in protein and a slight increase in fiber may begin to occur seven or eight days after spraying. Results of research work in the Peace River area support the demonstration results that protein may begin to decline and fiber content increases 7 or 8 days after spraying. The color of the forage begins to change from green to yellow 6 or 7 days after spraying.
When using Roundup® as a preharvest treatment and there is a heavy canopy of forage, an additional burn off may be required just before seeding the next crop. This may be especially true if a preharvest treatment is applied to a first cut of hay. Old pastures being removed from the rotation can be sprayed with a preharvest treatment of Roundup®, wait for 3 or 4 days, graze and then seed for greenfeed or silage.
Using Roundup® as a preharvest treatment at the first cut stage allows one to consider reseeding to spring or winter annuals that can be used for silage, greenfeed or swath grazing.
Direct seeded soils are cooler in the spring compared to conventional tilled soils. The major nutrients (nitrogen, phosphorus, potassium and sulphur) can be less available to crops under cooler temperature conditions. Some demonstrations involving conventional versus direct seeding have shown phosphorus and nitrogen deficiencies between the 3-4 leaf and tillering stage.
Placing as much fertilizer with the seed as possible without reducing crop emergence may help to reduce nutrient deficiency symptoms. The remainder of the fertilizer can be side banded. With the early deficiency problems observed in direct seeding demonstrations, direct seeded plots have yielded as well as conventional seeded crops. For more information on fertilizer requirements please consult an industry or government agronomist.
To date there has been limited success of seeding forages back to forages. This is especially true if the old forage crop was sod bound and contained a high percentage of grasses with fine leaves such as creeping red fescue. As with conventional tillage, our best results for re-establishing forages occur when annual crops are grown 1 or 2 years before re-establishing forages.
Direct seeding drills with disc type openers or narrow knives will provide the best results when seeding into previously treated forage stands. A drill that leaves a 2 to 3 inch wide strip of bare soil may assist in warming the soil reducing the possible effects of soil borne disease organisms.
When seeding into a heavy sod, ensure there is good seed to soil contact. Adjustments may be required on the packer wheel to ensure good seed to soil contact.