Progress 10/01/00 to 09/30/05
Outputs
Plant available soil K has generally been high in South Dakota. However in the last several years numerous reports of K deficiency on conventional till corn have been reported. Few potassium studies have been done in South Dakota. The objectives of these studies are: 1) Determine what rate of broadcast K can correct K deficiency on corn, 2) Determine if fertilizer placement influences grain yield response to K, 3) Determine if plant K deficiency is influenced by corn hybrid, and 4) Determine if an in-season K application can decrease K deficiency and increase grain yield. A summary of findings by objective for the five year study follows. 1) Significant grain yield responses from corn occurred at 1N NH4Ac extractable K soil test levels of 150 ug g-1 and lower. The rate of fertilizer K (as KCl) needed for maximum corn grain yield was not related to soil test K. A minimum application of 67 kg ha-1 K as KCl is suggested when soil test is below 150 ug g-1. 2) Efficiency of
placement of K for corn grain yield (either broadcast or 2 x 2 band) could not be determined because of water stress at three of the four sites. However, early growth was usually maximized for the band placement by about one half the rate of the broadcast-placed fertilizer K. 3) Response to added K is influenced by hybrid. However, all hybrids tested (20) responded to added K. It is concluded that management of plant potassium deficiency should be done with K additions and not hybrid selection. 4) In-season K application can decrease K deficiency and increase corn grain yield compared to no application. In-season K applications are dependent on subsequent rainfall and overall were not as efficient as pre-season K applications for producing corn grain. 5) Ear leaf K content was well correlated to soil test K and to relative corn grain yield at 29 sites from 1996 thru 2001. Critical ear leaf K content was determined to be 11 to 13 g kg-1 from either relationship. A tillage by soil test
K study was established in 2001 on a silt loam soil (initial soil K test of 110 mg kg-1) using a corn-soybean rotation. Treatment strips were established with conventional tillage and no-tillage using four soil test levels as the split-strip. Conventional tillage significantly increased both corn and soybean grain yield over no-till yields for the four years (0.44 and 0.28 Mg ha-1 for corn and soybean respectively). The first residual K soil test level (137 ug g-1) increased corn yield by 0.25 Mg ha-1 and 0.50 Mg ha-1 over the check K soil test (110 ug g-1) for conventional and no tillage, respectively. Higher soil test K levels did not increase corn yields further. Soybean did not respond to higher soil test K levels with either tillage system
Impacts
The impact of this study will be improved potassium nutrient management for corn and soybean by soil testing laboratories, fertilizer dealers, agronomists and other crop advisors. The expected impact eventually will improve producer crop economics. The South Dakota State University Soil Testing Laboratory has changed its soil test K recommendations. In addition, the Labs interpretation of K deficiency in corn based on ear leaf K content has decreased. Other Midwest soil testing laboratories may follow these recommendation changes. It is expected that crop advisors will now recommend in-season K applications to prevent large yield losses from K deficiencies on corn. Advisors will recognize that no-tillage systems are more sensitive to corn K deficiency than from a tilled system.
Publications
- Gelderman, R., J. Gerwing, and A. Bly. 2004. Response of corn and soybean to soil test K and tillage. Soil PR 04-12. Soil/Water Research, Pl. Sci. Paml. 21 (Revised 2005). Brookings: SDAES
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Progress 01/01/04 to 12/31/04
Outputs
Plant available soil K has generally been high in South Dakota. However in the last several years numerous reports of K deficiency on conventional till corn have been reported. Few potassium studies have been done in South Dakota. The objectives of these studies are: 1) Determine what rate of broadcast K can correct K deficiency on corn, 2) Determine if fertilizer placement influences grain yield response to K, 3) Determine if plant K deficiency is influenced by corn hybrid, and 4) Determine if an in-season K application can decrease K deficiency and increase grain yield. A tillage by soil test K study was established in 2001 on a Kranzburg silt loam (initial soil K test of 110 mg/kg) using a corn-soybean rotation. Treatments established were conventional tillage and no-till (strips) with four soil test levels as the split-strip. Soil test K levels averaged across both rotations and tillage systems in the fall of 2003 were 129, 163, 206, and 239 mg/kg. In 2004 V6 corn
plant dry weight was not significantly influenced by tillage or by K soil test or interaction of the two factors. Corn height at V12 was increased 13 cm by tillage and 13 and 38 cm by soil test K for the tilled and no-till systems, respectively. Corn grain yields (11.7 Mg/ha) were significantly decreased by less tillage and increased by increasing soil test K. Tillage produced 0.53 Mg/ha average increase in soybean yields while soil test K had no influence on yields. Average three-year yields for this study show a yield depression of 0.38 and 0.33 Mg/ha under no-till for corn and soybean, respectively. Potassium soil test level did little to increase corn and soybean yield under the tilled system. However, under the no-till system, soil test K of 140 mg/kg and greater increased average yields by 0.68 and 0.26 Mg/ha for corn and soybean, respectively.
Impacts
Corn growth was increased more by soil test K level under no tillage than under a tillage system. Average yields were less under a no tillage system.
Publications
- Gelderman, R., J. Gerwing, and A. Bly. 2003. Influence of potassium (K) rate, placement, and hybrid on K deficiency in corn. Soil PR 01-10. Soil/Water Research TB99 (Revised 2004). Brookings: SDAES
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Progress 01/01/03 to 12/31/03
Outputs
Plant available soil K has generally been high in South Dakota. However in the last several years numerous reports of K deficiency on conventional till corn have been reported. Few potassium studies have been done in South Dakota. The objectives of these studies are: 1) Determine what rate of broadcast K can correct K deficiency on corn, 2) Determine if fertilizer placement influences grain yield response to K, 3) Determine if plant K deficiency is influenced by corn hybrid, and 4) Determine if an in-season K application can decrease K deficiency and increase grain yield. A tillage by soil test K study was established in 2001 on a Kranzburg silt loam (initial soil K test of 110 mg/kg) using a corn-soybean rotation. Treatments established were conventional tillage and no-till (strips) with four soil test levels as the split-strip. Soil test K levels averaged across both rotations and tillage systems in the fall of 2002 were 114, 152, 203, and 244 mg/kg. In 2003 V6 corn
plant dry weight was significantly increased by tillage but not influenced by K soil test or interaction of the two factors. Corn height at V12 was increased by 18 to 20 cm by tillage and 5 to 8 cm by the first soil test level with no significant interaction of the two factors. Corn grain yields (9.4 Mg/ha) were not significantly influenced by treatments. Treatments did not influence R2 soybean plant wet weight. However, there was a significant 0.2 Mg/ha soybean grain increase from the first soil test level over control. Tillage produced 0.2 to 0.3 Mg/ha increase in soybean yields (2.4 Mg/ha) with no significant interaction between factors. Residual and current K applications were evaluated for increasing plant growth (V13 height and grain yield. A conventional tillage site was located on a Kranzburg silt loam with an initial soil test of 149 mg/kg K (High). Corn height was significantly increased by 5 to 8 cm due to added K (either residual or current). No significant corn grain
yield occurred due to treatment. A good relationship (r=0.88) was found between ear leaf K concentration and soil test K over 31 sites. These data produced a critical ear leaf K range of 11 to 15 g/kg as compared to the standard 17 g/kg currently used by many workers.
Impacts
Corn growth was influenced more by tillage than soil test K levels on a medium testing K soil. Soybean grain yield was increased both by tillage and soil test K level.
Publications
- Gelderman, R., Gerwing, J. and Bly, A. 2002. Influence of potassium (K) rate, placement, and hybrid on K deficiency in corn. Soil PR 01-10. Soil/Water Research TB99 (Revised 2003). Brookings: SDAES
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Progress 01/01/02 to 12/31/02
Outputs
Plant available soil K has generally been high in South Dakota. However in the last several years numerous reports of K deficiency on conventional till corn have been reported. Few potassium studies have been done in South Dakota. The objectives of these studies are: 1) Determine what rate of broadcast K can correct K deficiency on corn, 2) Determine if fertilizer placement influences grain yield response to K, 3) Determine if plant K deficiency is influenced by corn hybrid, and 4) Determine if an in-season K application can decrease K deficiency and increase grain yield. For objective one, a no-till site was located on an alluvial soil over sand in east central SD with a high (122ppm) K soil test (1N NH4Ac) . Treatments of 0, 34, 67, 101, and 134 kg K2O/ha as 0-0-60 were broadcast on the surface before being planted to corn. Treatments were replicated four times and arranged in a randomized complete-block design. Potassium significantly (P less than 0.10) increased
plant weight (V6), plant height (V9), and grain yield. Maximum grain yield occurred at the 134 kg K2O/ha rate. For objective two, one conventionally tilled site was located in east central South Dakota on loess soil over sand with a K soil test of 96 (medium) ug/g. Treatments of 0, 17, 34, 67, and 101 kg K20/ha as 0-0-60 were applied as a band (2x2 at planting) or broadcast incorporated. Treatments were arranged in a split plot randomized block design with four replications. Potassium rate was the whole plot and placement was the split. Grain yields averaged about 7211kg/ha (15% moisture) because of drought effects. Rate and placement of K and the interaction significantly influenced plant weight (V6), and plant height (V10). Only rate of applied K influenced grain yield. For objective three, one conventionally tilled, irrigated site was located in east central SD on an alluvial soil over gravel with a K soil test of 120 (medium) ug/g. Twenty similar maturity corn hybrids were planted
with and without K (45 kg K20/ha as 2 x 2 at planting). Treatments were arranged as a split plot with hybrid as the whole plot and K treatment as the split in a randomized block with four replications. Yields were lower than average because of lodging that occurred just prior to pollination. Hybrid and K application significantly influenced grain yield, however the interaction effect did not. Relative response to added K by hybrid ranged from 0-15%. For objective four, an in-season (V6 leaf stage) application of K2O (67 kg K2O/ha) was compared to a planting application at the site of objective one (above). Treatments were replicated four times and arranged in a randomized complete-block design. Time of K application had no significant influence on grain yield. Relative corn yield response to applied K was related to soil test at 37 sites over the years 1996-2002. A critical soil test K level of 150-160 ug/g was identified.
Impacts
Band placement of K is 3-4 times as efficient as broadcasting for increasing early plant growth. Most corn hybrids respond economically to added K. In-season K applications can be used to increase corn grain yields. Corn grain yield response to K is related to the 1N NH4Ac extractable K soil test with a critical level of 150 - 160 ug/g.
Publications
- Gelderman, R., J. Gerwing, and A. Bly. 2001. Influence of potassium (K) rate, placement, and hybrid on K deficiency in corn. Soil PR 01-9. Soil/Water Research TB99 (Revised 2002). Brookings: SDAES
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Progress 01/01/01 to 12/31/01
Outputs
Plant available soil K has generally been high in South Dakota. However in the last several years numerous reports of K deficiency on conventional till corn have been reported. Few potassium studies have been done in South Dakota. The objectives of these studies are: 1) Determine what rate of broadcast K can correct K deficiency on corn, 2) Determine if fertilizer placement influences grain yield response to K, 3) Determine if plant K deficiency is influenced by corn hybrid, and 4) Determine if an in-season K application can decrease K deficiency and increase grain yield. For objective one, two conventionally tilled sites were located on glacial till in NE and SE South Dakota with medium K soil tests (1N NH4Ac). One no-till site was located on a loess soil in SE SD with a very high K soil test. Treatments of 0, 67, 134, and 268 kg K20/ha as 0-0-60 were broadcast and incorporated before being planted to corn for the conventionally tilled sites. Potassium treatments
were broadcast on the surface for the no-till site. Treatments were replicated four times and arranged in a randomized complete-block design. Potassium significantly (P less than 0.10) increased grain yields at one site. Maximum yield occurred between the 0 and 67 kg K20/ha rate. For objective two, one conventionally tilled site was located in east central South Dakota on a glacial out wash soil with a K soil test of 80 ug/g. Treatments of 0, 17, 34, 67, and 101 kg K20/ha as 0-0-60 were applied as a band (2x2 at planting) or broadcast incorporated. Treatments were arranged in a split plot randomized block design with four replications. Potassium rate was the whole plot and placement was the split. Grain yields were low and variable due to rootworm infestation and drought. No significant treatment effects were measured on grain yield. For objective three, one conventionally tilled site was located in east central SD on a glacial out wash soil with a K soil test of 104 ug/g. Twenty
similar maturity corn hybrids were planted with and without K (40 kg K20/ha as 2 x 2 at planting). Treatments were arranged as a split plot with hybrid as the whole plot and K treatment as the split in a randomized block with four replications. Yields were low because of rootworm and drought effects. Hybrid and K application significantly influenced grain yield, as did the interaction. Relative response to added K by hybrid ranged from 7-54%. For objective four, an in-season (V6 leaf stage) application time was compared to a planting application on two sites (conventional-NE and no-till, SE as above in objective one). Treatments were arranged in a split-plot design with rate as the whole plot and time of application as the split in a randomized block with four replications. Applied K increased grain yield at only the conventionally tilled site with either application time. However, grain yield for the spring applied K treatments averaged 878 kg/ha over the V6 application. Relative
corn yield response to applied K was related to soil test at 33 sites over the years 1996-2001. A critical soil test K level of 150-160 ug/g was identified.
Impacts
The most efficient K2O broadcast rate for grain yield is approximately 67 kg/ha. Most hybrids respond economically to added K. In-season K applications can be used to increase corn grain yields. Corn grain yield response to K is related to the 1N NH4Ac extractable K soil test with a critical level of 150 - 160 ug/g.
Publications
- Gelderman, R., J. Gerwing, and A. Bly. 2000. Influence of potassium (K) rate, placement, and hybrid on K deficiency in corn. Soil PR 00-8. Soil/Water Research TB99 (Revised 2001). Brookings: SDAES
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Progress 01/01/00 to 12/31/00
Outputs
Plant available soil K has generally been high in South Dakota. However in the last several years numerous reports of K deficiency on conventional till corn have been reported. Few potassium studies have been done in South Dakota because of the relatively few deficient soils in the state. The objectives of these studies are: 1) Determine what rate of broadcast K can correct K deficiency symptoms on conventionally tilled fields, 2) Determine if fertilizer placement influences grain yield response to potassium, 3) Determine if plant K deficiency is influenced by corn hybrid, and 4) Determine if an in-season K application can decrease K deficiency and increase grain yield. For objective one, four conventionally tilled sites were located on glacial outwash (3) or glacial till (1) soils with medium to high soil K tests (1N NH4Ac). Treatments of 0, 67, 134, and 268 kg K20/ha as 0-0-60 were broadcast and incorporated before being planted to corn. Treatments were replicated
four times and arranged in a Latin square design. Potassium significantly (P less than 0.10) increased grain yields at two sites. Maximum yield occurred between the 0 and 67 kg K20/ha rate at both locations. For objective two, one conventionally tilled site was located in east central South Dakota on a glacial outwash soil with a K soil test of 126 ug/g. Treatments of 0, 17, 34, 68 and 101 kg K20/ha as 0-0-60 were applied as a band (2x2 at planting) or broadcast incorporated. Treatments were arranged in a split plot randomized block design with four replications. Potassium rate was the whole plot and placement was the split. Broadcasting between 34 and 67 kg K20/ha and banding between 17 and 34 kg K20/ha maximized corn grain yields. For objective three, one conventionally tilled site was located in east central SD on a glacial outwash soil with a K soil test of 114 ug/g. Twenty similar maturity corn hybrids were planted with and without K (45 kg K20/ha as 2 x 2 at planting).
Treatments were arranged as a split plot with hybrid as the whole plot and K treatment as the split in a randomized block with four replications. Hybrid and K application significantly influenced grain yield but the interaction did not. Relative response to added K by hybrid ranged from 2-32%. For objective four, a conventionally tilled site with plants exhibiting K deficiency was selected on a glacial outwash soil with a K soil test of 73 ug/g (low). Treatments of 0 and 112 kg K20/ha were surface broadcast and shallowly incorporated at V6 stage of corn growth. Four replications were arranged in a complete block design. In-season applied K significantly increased grain yield over check by 1944 kg/ha. Relative corn yield response to applied K was related to soil test at 28 sites over the years 1996-2000. A critical soil test K level of 150-160 ug/g was identified from this relationship.
Impacts
Banding K is more effective for increasing grain yield than broadcasting in conventionally tilled corn. Most hybrids respond similarly to added K. Corn grain yield response to K is related to the 1N NH4Ac extractable K soil test with a critical level of 150 - 160 ug/g.
Publications
- Gelderman, R., J. Gerwing, and A. Bly. 1999. Potassium fertilizer rate and placement effects on corn. Soil PR 99-11. Soil/Water Research TB99 (Revised 2000). Brookings: SDAES
- Gelderman, R., J.R Gerwing and A. Bly. 2000. Potassium Deficiency in South Dakota. Vol. 16, p 117 in (J.Gerwing ed.) Thirtieth North Central Extension-Industry Soil Fertility Conference. St. Louis, MO Nov. 15 - 16. 2000. PPI, Brookings, SD 57006.
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