Progress 07/01/02 to 06/30/06
Outputs
Current methodologies to estimate the behavior of soil test phosphorus (STP) and yield response upon phosphorus (P) fertilizer additions involve small plot studies. The assumption that is made is that entire fields are 'scaled up' small plot studies. Due to the variation in the chemical and physical properties of soils over the landscape, small plot studies may not provide a good estimate of whole field behavior. The objectives of this study were: 1) to compare the yield obtained from applications of P fertilizer in small plot and whole field studies; 2) estimate changes in STP upon net P additions; and 3) determine if data collected from small plot studies is a good estimate of whole field behavior. Average corn yield across all sites increased with 10 kg P ha-1, but did not increase substantially with additional P fertilizer. When yield responses were separated based on soil test phosphorus (STP), the data suggest that greater yield was obtained with higher initial
STP, and additional P fertilizer does not appear to compensate for low STP values. Soybean yield across all study sites did not respond to added P fertilizer as dramatically as corn did, but at STP values < 10 there was a much greater response to the 10 kg P ha-1 rate. Similar to corn, soybeans produced the greatest yields at the highest initial STP values. Sorghum yields across all study sites responded to the 10 kg P ha-1 treatment when STP values were > 10. These yield data were collected using yield monitors from unconventional experimental designs, presenting a challenge and opportunity in data interpretation. Additional studies have looked at other aspects of P fertilitiy. We have conducted P management studies on corn (5 locations) and grain sorghum (5 locations). With these studies we gathered additional information on P soil test correlation (4 extractants/procedures) and effect of P application rate on grain P removal and change in soil test values over time. Grain P content
varied location to location and in relationship to P application rate and/or P soil test value. Results from small plot studies indicate that no response to the addition of P fertilizer occurred in the year of P fertilizer application (year 1) or in the residual phase (year 2). However, responses were observed in one out of five whole field studies in year 1 and four out of five studies in year 2, suggesting that small plot yield data may not represent P response across an entire field. Soil test P concentrations were unaffected by net P additions in all small plot studies, but one, in years 1 and 2. However, linear and quadratic contrasts were not significant for the study, indicating that no trend existed. One in five whole field sites in year 1 and two of five sites in year 2 had significant changes in STP due to net P additions with a quadratic trend. Whole field studies confirm that small plot studies have shortcomings when estimating whole field behavior. This is primarily due
to variability in the chemical and physical properties of soils that exist across the landscape, which are difficult to ascertain on such a small scale.
Impacts
Results vary from one field to the other, which is an argument for farmers to be collecting these types of data and have someone interpret the results for them. The other important impact is that this is an exercise in how we can use this type of data (whole field) to help the producer make some decisions about his or her own P fertility management. This approach to data analysis is an example of the research paradigm shift required to exploit precision agriculture technologies for modifying production input models. Work on various P soil test extractants/procedures has provided needed documentation for interpreting these soil tests in Kansas.
Publications
- Baker, L. R. 2005. Use of Precision Agriculture to Improve Phosphorus Management. MS Thesis, Kansas State University.
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Progress 01/01/05 to 12/31/05
Outputs
Current methodologies to estimate the behavior of soil test phosphorus (STP) and yield response upon phosphorus (P) fertilizer additions involve small plot studies. The assumption that is made is that entire fields are scaled up small plot studies. Due to the variation in the chemical and physical properties of soils over the landscape, small plot studies may not provide a good estimate of whole field behavior. Recent observations in the spatial variability of soil properties and grain yields have generated more interest in the use of precision agriculture to collect whole field data to estimate the potential response of STP and grain yield to P fertilization. The objectives of this study were: 1) to compare the yield obtained from applications of P fertilizer in small plot and whole field studies; 2) estimate changes in STP upon net P additions; and 3) determine if data collected from small plot studies is a good estimate of whole field behavior. Results from small
plot studies indicate that no response to the addition of P fertilizer occurred in the year of P fertilizer application (year 1) or in the residual phase (year 2). However, responses were observed in one out of five whole field studies in year 1 and four out of five studies in year 2, suggesting that small plot yield data may not represent P response across an entire field. Soil test P concentrations were unaffected by net P additions in all small plot studies, but one, in years 1 and 2. However, linear and quadratic contrasts were not significant for the study, indicating that no trend existed. One in five whole field sites in year 1 and two of five sites in year 2 had significant changes in STP due to net P additions with a quadratic trend. Whole field studies confirm that small plot studies have shortcomings when estimating whole field behavior. This is primarily due to variability in the chemical and physical properties of soils that exist across the landscape, which are difficult
to ascertain on such a small scale.
Impacts
One impact is that the results seem to vary from one field to the other, which is an argument for farmers to be collecting these types of data and have someone interpret the results for them. The other important impact is that this is an exercise in how we can use this type of data (whole field) to help the producer make some decisions about his or her own P fertility management. This approach to data analysis is an example of the research paradigm shift required to exploit precision agriculture technologies for modifying production input models. Work on various P soil test extractants/procedures has provided needed documentation for interpreting these soil tests in Kansas.
Publications
- Schmidt, J., R. Gehl, L. Baker, L. Maddox, and D. Leikam. 2003. Whole-field evaluation of yield and soil test P response to phosphorus fertilizer. Abstracts of the SSSA Meetings, Denver, Colorado
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Progress 01/01/04 to 12/31/04
Outputs
Average corn yield across all sites increased with 10 kg P ha-1, but did not increase substantially with additional P fertilizer. When yield responses were separated based on soil test phosphorus (STP), the data suggest that greater yield was obtained with higher initial STP, and additional P fertilizer does not appear to compensate for low STP values. The combination of high STP values and high P application rates may actually depress yield somewhat in corn especially in dry years. Soybean yield across all study sites does not seem to respond to added P fertilizer as dramatically as corn does, but at STP values < 10 there seems to be a much greater response to the 10 kg P ha-1 rate. Similar to corn, the soybeans produced the greatest yields at the highest initial STP values implying that P fertilizer can not totally compensate for low STP values. Sorghum yield across all study sites responded to the 10 kg P ha-1 treatment when STP values were > 10. Similar to corn
and soybeans, it appears that P fertilizers can not compensate for low initial STP values. These yield data were collected using yield monitors from unconventional experimental designs, presenting a challenge and opportunity in data interpretation. One opportunity is evaluating data along a transect for the length of the field. Average corn yield from the 60 kg P ha-1 residual treatment was 1.24 Mg ha-1 greater than compared to the control and the 20 kg P ha-1 residual treatment was 0.93 Mg ha-1 greater than the control; however, most of this increase occurred in a portion of the field from 192 m to 544 m, representing an average increase of 1.47 Mg ha-1 for the 60 kg P treatment and 1.10 Mg ha-1 for the 20 kg ha-1 treatment over the area. The yield response to the 10 and 40 kg P ha-1 residual treatments are similar. However, the 10 kg P treatment is similar to the control treatment, which implies that it is not supplying enough P to produce maximum corn yields in the residual year.
Average sorghum yield response at the KSU and Clay County sites were similar to the response observed in corn and soybeans. The 20 kg P ha-1 treatment gave the largest yield response. The KSU site has been in no-till for only two years and the Clay County site has been managed under no-till for >10 years. The response to applied P in the newly established no-till (3.08 to 3.41 Mg ha-1) is less than that of the long term no-till field (2.68 to 3.74 Mg ha-1). This large response in long term no-till is probably due to cool, wet soils and P stratification that is often observed in no-till. Additional studies have looked at other aspects of P fertility. During the past year we have conducted P management studies on corn and grain sorghum (5 locations each). With these studies we are gathering additional information on P soil test correlation and the effect of P application rate on grain P removal and change in soil test values over time. Grain P content has varied location to location and
in relationship to P application rate and/or P soil test value.
Impacts
One impact is that the results seem to vary from one field to the other, which is an argument for farmers to be collecting these types of data and have someone interpret the results for them. The other important impact is that this is an exercise in how we can use this type of data (whole field) to help the producer make some decisions about his own P fertility management. This approach to data analysis is an example of the research paradigm shift required to exploit precision agriculture technologies for modifying production input models. Work on various P soil test extractants/procedures has provided needed documentation for interpreting these soil tests in Kansas.
Publications
- No publications reported this period
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Progress 01/01/03 to 12/31/03
Outputs
Five fields were identified in 2002, 433 soil samples collected from these fields, and P fertilizer applied, as preliminary work to this study. In 2003, an additional eight fields were identified, 639 soil samples collected, and fertilizer applied. Many of the 639 soil samples collected in 2003 were from fields managed under no-till, so about one-fourth of these samples were collected from 0-2, 2-4, and 4-6 inch depths. Soil samples were collected from the initial five fields for a second time in 2003. Additionally, soil samples were collected monthly at three field sites. Preliminary results are available from fields identified and sampled in 2002. Five farmers are currently participating and additional cooperators will be identified for the next couple years of the study. Small-plot studies have been established in five fields this year. Average corn yield at the Topeka Field increased with 20 lb P2O5 per acre, but did not increase substantially with additional P
fertilizer. Average soil test P (STP) prior to fertilizer application was 11 mg per kg (Bray 1), ranging from 4 to 60 mg per kg and > 75 % of the samples had STP < 10 mg per kg. When yield responses were separated based on STP, the data suggest that greater yield was obtained with greater STP, and additional P fertilizer did not appear to compensate for low STP, at least in the year of fertilizer application. However, interpretation of these results must be approached with caution because treatments have not been randomized and significant differences have not yet been determined. Soybean yield in the other half of the same field at Topeka did not show the dramatic increase in yield with 20 lb P2O5 per acre, but with lower STP the yield response appeared more substantial. These yield data were collected using yield monitors from unconventional experimental designs, presenting a challenge and opportunity in data interpretation. One of the opportunities is evaluating data along a
transect (treatment strip) for the length of the field. Average soybean yield from the 120 lb P2O5 treatment was 3.0 bu per acre greater than compared to the control; however, most of this increase occurred in a portion of the field > 1000 ft from the west end of the field, representing an average increase of 7.6 bu per acre in this area. The yield response to the 40 and 80 lb P2O5 rates in this area was similar. This approach to data analysis and other unconventional (but statistically valid) approaches will be some of the exciting components of this project, and are examples of the research paradigm shift required to exploit precision agriculture technologies for modifying production input models. Average soybean yield response at another field and average grain sorghum yield response at the a third field were similar to the response observed at the Topeka Field. Average initial STP at these fields was 34 mg per kg and 15 mg per kg, respectively. More detailed data analyses
(spatially) have not been completed at these and other fields.
Impacts
Results from this project will be used to improve P fertilizer recommendations, which will improve the economic return for all Kansas? producers. Fertilizer recommendations will include a method for optimizing economic return to P fertilizer assuming some length of land tenure (this has never before been available). Success of this study would be a model for future on-farm / university research.
Publications
- Kastens, T.L., J.P. Schmidt, and K.C. Dhuyvetter. 2003. Yield Models Implied by Traditional Fertilizer Recommendations and a Framework for Including Non-traditional Information. Soil Sci. Soc. Am. J. 67:351-364.
- Schmidt, J., R. Gehl, L. Maddux, D. Leikam, and L. Baker. 2003. Whole-field Evaluation of Yield Response to Phosphorus Fertilizer. p. Agronomy Abstracts. ASA, Madison, WI.
- Schmidt, J., R. Taylor, T. Kastens, K. Dhuyvetter, and S. Staggenborg. 2003. A New Paradigm for On-farm Research in Kansas. p. Agronomy Abstracts. ASA, Madison, WI.
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Progress 01/01/02 to 12/31/02
Outputs
This project was initiated during the summer / fall of 2002, so there are few results or accomplishments on which to report. Five field sites have been identified with four cooperators and one field site has been established at the Kansas River Valley (KRV) Experiment Field. Georeferenced soil samples were collected at each site and phosphorus determined for each sample. Combines equipped with a yield monitor and global position system were used to collect yield data at every site. Grain yield was also determined at the KRV site by hand harvesting at every soil sample location. Three additional sites have been identified at which soil samples have been collected on monthly intervals since April 2002. We are in the process of identifying a graduate student for this project and plan to identify additional field sites prior to the 2003 growing season.
Impacts
Results from this project will be used to improve P fertilizer recommendations, which will improve the economic return for all Kansas? producers. Fertilizer recommendations will include a method for optimizing economic return to P fertilizer assuming some length of land tenure (this has never before been available). Success of this study would be a model for future on-farm / university research.
Publications
- No publications reported this period
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