368 Ag Hall OSU Plant & Soil Sciences Department
Stillwater, OK 74078 |
NEWS |
CONTENTS OF NEWSLETTER
We welcome contributions and suggestions. Comments about and
contributions to the NEWS are welcome and can be submitted to any of the directors. |
Time: Place: Welcome -- Opening Remarks -- Nitrate Toxicity: You CAN Kill Your Cattle! Alfalfa, Queen of Forages, Deserves a Royal Treatment Weeds: Does It Pay to Control Them? Grazing Wheat Pasture: What Have We Learned? Economics of Hay Harvesting and Feeding Cool-Season Perennial Grass UPDATE SPONSORED BY |
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| The most common nutrient deficiency in Oklahoma alfalfa production is phosphorus.
Potassium, although used in amounts five times greater than phosphorus by alfalfa, is
often adequately supplied by soils in central and western Oklahoma, where most alfalfa is
grown. Lime is commonly needed to bring acid soils to a pH where production will not be
limited (above pH 6.2), but once applied the lime lasts for the life of most stands.
A recent soil test is the most reliable way to determine if lime, potassium, or phosphorus need to be applied. When soil deficiencies exist, what is the most economical way to correct them? This is an important question for alfalfa producers because phosphate applied to the soil surface only moves a fraction of an inch into the soil by irrigation or rainfall. Therefore, to be most effective, phosphate should be applied broadcast and incorporated preplant. However, the reaction of phosphate fertilizer with soil that limits its being washed into the soil, also reduces its residual (or carryover) benefits from one year to the next. So, the "bottom line" question becomes, "does the benefit of incorporating more than one seasons need of phosphate fertilizer preplant, outweigh the decrease in phosphate availability that occurs in the soil over time". The OSU recommendation has been to apply two to three year's requirement preplant if you could afford it, because the response was slightly better than annual surface applications after establishment. We now have four years of yield data from a phosphorus fertilizer study at Chickasha to support recommending several year's phosphorus needs preplant. Table 1 shows the 4-year total yields for three different phosphate rates compared to a check plot. The soil test P index was about 35 (85 % sufficient) and called for about 80 lb P2O5/acre/year for the area. Note that the unfertilized check averaged more than 5 ton per acre per year (a good yield by most standards). When 200 lb P2O5/acre was applied for the four year period (100 lb preplant and 100 lb in the third year) the yield increased by 1.9 tons. This represented a $100 per acre profit for the period ($25 per acre per year) from applying the fertilizer, when alfalfa is valued at $80 per ton and P2O5 costs $0.26 per pound. Using higher rates of phosphate increased yield and profit. When the rate was increased to 400 lb P2O5 per acre (200 preplant and 200 in the third year) yield increased and "profit" increased $44 per acre from the additional 200 lb of P2O5. Adding a six-year supply, all preplant incorporated further increased yield, and profit went up another $36 per acre. From these results it is obvious that when it is affordable, applying extra phosphate preplant is a profitable practice if the soil test indicates a deficiency. Table 1. Four-year alfalfa response to preplant and annual applications of phosphate fertilizer
*Calculated as marginal return from fertilizer using P2O5 from 18-46-0 at $0.26/lb and alfalfa at $80/ton. Harvest costs and fertilizer application costs are not included. Phosphate was also applied as a preplant band, and as preplant band plus later band injections to see if minimizing soil-fertilizer reaction by band application would increase the alfalfa response. Banding was done by injecting liquid ammonium polyphosphate at a six-inch depth in bands 20 inches apart. Table 2 shows an increase in yield and "profit" when phosphate is banded compared to broadcast applied. It appears the 200 lb rate is most profitable, and could markedly increase the return on fertilizer investment. The added "profit" from banding is large enough to cause one to consider this non-traditional practice when equipment and capital are available. Since application costs are not included, and the 600 lb rate only needs to be applied once, the difference between three 200 lb applications and one 600 lb application may be minimal after six years. Table 2. Four-year alfalfa response to preplant broadcast and banded applications of phosphate fertilizer
*Calculated as marginal return from fertilizer using P2O5 from 18-46-0 (for broadcast) at $0.26/lb and from 10-34-0 (for banding) at $0.34/lb, and alfalfa at $80/ton. Harvest costs and fertilizer application costs are not included. |
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Gordon Johnson Extension Nutrient Management Specialist |
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| The following list of activities is for those who did not keep the list handed out at
the annual meeting last month. The Association had a lot of activities last year. You
might use this list to help attract new members for the Association. Membership has grown
during the last several years, but we can always use more members. There are several
hundred non-members around the state who could benefit by joining. Members should also use
this list of activities to think of things the Association did not do. Tell the
directors (listed on the last page) of other things you think we should try. Take a few
minutes to promote the Association among your friends and business associates. Annual Meeting (February), Alfalfa Congress (July), Alfalfa EXPO (November), Association Directory Record numbers in all membership classes in 1996: Total Membership -- over 350 Hosted the Southern Pasture & Forage Crop Conference in March Hosted the North American Alfalfa Improvement Conference in June The "NEWS" received a Certificate of Excellence from the Extension Division of the American Society of Agronomy. "Alfalfa Harvest Management Discussions with Cost-Benefit Analysis", published in 1995 and co-sponsored by the Oklahoma Alfalfa Hay & Seed Association and Okla. Extension Service was awarded a Certificate of Excellence by the Extension Division of the American Society of Agronomy. Brought in more than $30,000 from Fund-Raising Auctions (Feb. and Nov.) Sponsored research conducted by the Alfalfa Integrated Management team -- more than $5000. Sponsored Station Tours and County or Regional Educational Meetings with the Okla. Cooperative Extension Service and Okla. Agric. Experiment Station. Expanded the Association's Home Page on the Internet. Used Caps and Bumper Stickers to promote the Association. |
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| Balances 1-1-96 $ 8,115 For members who would like to see a detailed breakdown of the budget, please ask one of the directors. Income -- $ 30,598 Expenses -- $ 25,242 |
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| "Control of Cool Season Weeds" --It is too late to control
cool-season broadleaf weeds and weedy grasses in established alfalfa with SINBAR and
VELPAR. Alfalfa has started growing and alfalfa damage can result with applications to
growing alfalfa plants. Also, many of the weeds are starting to flower and getting too
large to control. It is also too late to control most cool-season weeds in fall-planted alfalfa with 2,4-DB (BUTYRAC 200) and POST PLUS. Probably the only good option now for control of cool-season weeds is to mow early (some time in April) before the weeds get to mature or large and start shading the alfalfa. "Control of Summer Weeds" --Many of you are still asking what can be used to control those *#*^> pigweed and grasses. The good news is that we are getting more herbicide options every year. However, the bad news is that options are not always dependable and quite often, not economical. Herbicides that can be applied now for summer weed control would include: TREFLAN EC is an effective preemergent herbicide for control of both pigweeds and weedy grasses if you can get a good herbicide dose rate into the soil before summer weeds germinate. Crabgrass and foxtail start germinating in April and pigweed in May. TREFLAN is an old dependable herbicide that has been available for many years. The problem is it has is to be mechanically incorporated or watered in quickly. Good incorporation of TREFLAN EC is possible by using chemigation (applying herbicide in irrigation water). It requires putting on 2 to 4 pints/acre of TREFLAN EC on with at least ½ inch of water, preferably on a cool cloudy day to minimize losses. Then, I would suggest that another couple of inches of water be applied as soon as possible to maximize moving the TREFLAN into the soil. There is a 21-day grazing and haying restriction after application, so you will need to apply it soon. TREFLAN does not leach down in soil and has good residual activity, providing you get good incorporation with the watering. Cost for 3 pt/A of TREFLAN EC would be approximately $10.70. ZORIAL RAPID 80 in a preemergent herbicide that received Supplemental Labeling in September of 1996. We first evaluated it for weed control in 1985 and since have evaluated it in some 25 trials. It has little if any activity on emerged weeds, so it is critical to get it applied and incorporated by rain before weeds emerge. ZORIAL has good activity on crabgrass and foxtail, but only fair on pigweeds. Our most consistent control resulted from 2.5 lb/acre applied in February and March. Lower rates did not give consistent all-summer control and applications made after 1st harvest were often too late since summer weeds had already emerged. Current label rates are 1.25 to 2.5 lb/acre. At the going cost of $16.85/lb, that is $20.31 to $40.62/acre for herbicide cost. I believe it will have a place after 1st harvest in combination with a postemergent herbicide that will control emerged weeds. My advise is to use only on trial basis until we work out some of the kinks. More on summer weed control in April. |
-- Jim Stritzke Alfalfa Weed Control Specialist |
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