1 / 19

Peter Motavalli, Kelly Nelson, and Manjula Nathan University of Missouri

SOYBEAN RESPONSE TO PRE-PLANT AND FOLIAR-APPLIED POTASSIUM. Peter Motavalli, Kelly Nelson, and Manjula Nathan University of Missouri Email: motavallip@missouri.edu. INCREASING K DEFICIENCY. Increasing K deficiency in agronomic crops in Missouri and other Midwestern states:.

devaki
Download Presentation

Peter Motavalli, Kelly Nelson, and Manjula Nathan University of Missouri

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. SOYBEAN RESPONSE TO PRE-PLANT AND FOLIAR-APPLIED POTASSIUM Peter Motavalli, Kelly Nelson, and Manjula Nathan University of Missouri Email: motavallip@missouri.edu

  2. INCREASING K DEFICIENCY Increasing K deficiency in agronomic crops in Missouri and other Midwestern states: • Decrease in soil K availability due to drought conditions and soil compaction. • Reductions in applied K fertilizer and the frequency of soil testing by producers due to decreasing commodity prices. • Higher corn yields and increasing soybean acreage in rotation with corn has increased K fertilizer requirements.

  3. BACKGROUND RESEARCH: • Response to foliar N-P-K-S fertilizers applied to soybeans has been inconsistent with both observed increases and decreases in yields. Early emphasis was on targeting foliar fertilization during reproductive growth stages. • One group found that foliar application at the R2 to R7 growth stages at a 10-1-3-0.5 ratio was optimum (Garcia and Hanway, 1976).

  4. BACKGROUND RESEARCH: • A recent 3-year study in Iowa with 48 trials of foliar N-P-K fertilization of soybean at early vegetative growth stages (approx. V5) on different soil resources observed 7 sites with increased yields and 2 sites with decreased yields (Haq and Mallarino, 1998 and 2000). • Yield response tended to occur in soils with high CEC, when soil test P was low and when rainfall in spring and midsummer was low.

  5. OBJECTIVES: • To examine improvements in crop yield and other agronomic benefits of applying pre-plant and foliar K fertilizer at different times during the growing season. • To compare the use of different soil test K extractants (i.e. ammonium acetate and sodium tetraphenylboron) and their relationship with crop response.

  6. MATERIALS AND METHODS: • Two-year field trial initiated in 2001 in a cooperator’s farm field southeast of Greenley Agronomy Center on a claypan soil. • No-till planted Asgrow 3701 Roundup Ready soybeans both years (7.5 inch rows at 200,000 seeds/acre).

  7. MATERIALS AND METHODS: • 4 rates of pre-plant K fertilizer (0, 125, 250 and 500 lbs K/acre as potassium sulfate) broadcast-applied. • 3 additional K rates (8, 16 and 32 lbs K/acre as potassium sulfate) foliar-applied at 3 separate times (V4, R1-R2, and R3-R4 soybean growth stages). • Had foliar checks of magnesium sulfate. • Foliar application was 60 gallons/acre.

  8. INITIAL SOIL CHARACTERISTICS: pH Bray-1 Exchangeable Year (0.01 M CaCl2)OM P K Ca Mg - % - ------------- lbs/Acre ------------- 2001 7.2 3.6 30 148 5241 559 2002 7.1 2.9 43 143 7020 636 Desired Soil Test K Level = 220 + (5 x CEC) For 2001 = 298 lbs K/Acre For 2002 = 322 lbs K/Acre

  9. SOIL TEST K FROM TREATMENTS: Sampled June, 2001 Pre-plant Exchangeable K Applied K --- lbs/Acre --- 0 lbs K/Acre 146 125 168 250 185 500 217

  10. 2001 RESULTS - GREENLEY Pre-plant K Check

  11. 2002 RESULTS - GREENLEY Check Pre-plant K

  12. 60 LSD (0.05) 45 30 15 0 Preplant Applied Foliar Applied 2001 RESULTS - YIELD 500 lbs K/acre 250 125 32 32 16 8 32 16 16 Soybean 8 S0 0 S0 8 yield S0 (bu/acre) V4 R3-R4 R1-R2

  13. 60 45 Soybean yield 30 (bu/acre) 15 0 2002 RESULTS - YIELD 500 lbs K/acre 250 LSD 125 (0.05) 32 32 16 16 8 8 32 16 8 S0 S0 0 S0 R3- R4 V4 R1-R2 Preplant Applied Foliar Applied

  14. SALT INJURY RATINGS: • Potassium fertilizers, such as muriate of potash (KCl), have a high salt index and therefore can cause salt injury when foliar-applied. • Potassium sulfate has a lower salt index (46) compared to KCl (116). • Leaf injury ratings in 2001 and 2002 showed minimal to no effects of foliar application of potassium sulfate at application rates used in this study.

  15. Ammonium acetate K (lbs/acre) SOIL TEST K EXTRACTANTS 350 2001 300 2002 250 200 Y = 0.26X + 47.6 2 R = 0.85***, n = 32 150 100 250 500 750 1000 1250 Sodium tetraphenylboron K (lbs/acre)

  16. 100 80 Relative 2 Y = -0.0038X + 1.92X - 154 yield (if X>253 then Y = 89) (%) 60 2 R = 0.64***, n = 32 40 20 100 150 200 250 300 350 RELATIONSHIP WITH SOIL TEST K Ammonium Acetate Soil test K (lbs/acre)

  17. 100 80 Relative yield (%) 60 40 20 RELATIONSHIP WITH SOIL TEST K Sodium Tetraphenylboron 2 Y = -0.00087X + 1.08X - 253 (if X>621 then Y = 82) 2 R = 0.52***, n = 32 250 500 750 1000 1250 Soil test K (lbs/acre)

  18. CONCLUSIONS • Foliar K applications in soybeans may be a possible management tool to mitigate reduced yields caused by K deficiency. • However, highest yields were obtained with pre-plant K fertilizer applications. • Need additional testing of this approach at other locations and under different climatic conditions in Missouri to confirm these results and evaluate potential economic benefits.

  19. CONCLUSIONS • Further testing to identify most practical foliar K source(s): • Solubility • Crop response • Compatibility with post-emergence herbicides • Effectiveness of K source/herbicide mix for weed control • Cost effectiveness

More Related