Source: UNIV OF WISCONSIN submitted to
SOIL RESEARCH
Sponsoring Institution
State Agricultural Experiment Station
Project Status
TERMINATED
Funding Source
Reporting Frequency
Annual
Accession No.
0204054
Grant No.
(N/A)
Project No.
WIS04932
Proposal No.
(N/A)
Multistate No.
(N/A)
Program Code
(N/A)
Project Start Date
Oct 1, 2004
Project End Date
Sep 30, 2011
Grant Year
(N/A)
Project Director
Laboski, C. A.
Recipient Organization
UNIV OF WISCONSIN
21 N PARK ST STE 6401
MADISON,WI 53715-1218
Performing Department
SOIL SCIENCE
Non Technical Summary
Agriculture is under increased pressure to control nutrient losses to the environment. Managing nutrients to supply adequate amounts for crop production must be balanced with potential over application which reduces water and air quality. The purpose of this research is to improve our scientific knowledge about nutrient cycling in agricultural systems, and subsequently to improve nutrient application recommendations that will improve the environmental, agronomic, and economic sustainability of agriculture in Wisconsin.
Animal Health Component
80%
Research Effort Categories
Basic
10%
Applied
80%
Developmental
10%
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
1020110206160%
1021310206110%
1021599206110%
1021699206110%
1025210206110%
Goals / Objectives
The main focus of my research program is to improve our knowledge about soil fertility and nutrient management such that the agronomic, economic, and environmental sustainability of agricultural production in Wisconsin is improved. Specific objectives include: 1) Understand the availability of nutrients from manure to crops and potential environmental consequences of manure application. Manure nutrient availability is known to vary depending on animal species, manure storage, animal diet, application method, and soil type. Developing a matrix of nutrient availabilities from various manures produced and applied to the range of soils in Wisconsin is necessary to reduce the environmental impact of manure nutrients through improved recommendations and best management practices. 2) Research alternate soil analyses to current routine soil tests that will produce indices of nutrient availability which provide an improved basis for nutrient recommendations. Soil testing is our best method for determining how much nutrients are needed for crop production. However, soil testing is not perfect in that improvements can always be made with regard to the type of method used and interpretation of the subsequent data for making nutrient recommendations. 3) Assess methods to improve soil nutrient availability to crops such that fertilizer use may be reduced and water quality subsequently increased. Many soils contain high levels of nutrients from repeated manure and fertilizer application. However, some crops may still respond to nutrient additions even at high soil test levels. This indicates that the soil supplying capacity can not keep up with crop demand. Finding alternative methods to improve availability of soil nutrients such that additional nutrient applications are not needed will reduce the potential of nutrient loss to the environment and improve farm economics. Various aspects of the research program will focus on phosphorus, nitrogen, potassium, and liming.
Project Methods
Both field and laboratory research methods will be used to meet the objectives. For objective 1, field based studies will compare crop and soil response to applied manure vs. fertilizer with regard to changes in soil test levels, plant tissue nutrient content, and crop yield. As field studies of this nature are expensive and time consuming, laboratory incubations will be conducted with similar manures and fertilizers to assess how well correlated laboratory data is to field data. If lab and field data are well correlated, then a large lab experiment can be done to assess the nutrient availability of manure compared to fertilizer for a wide range of manure types and soils found in Wisconsin. A larger laboratory based study can provide data more quickly and economically than field based studies. The approach for objective 2 is to determine how new laboratory analyses predict crop nutrient needs. The new analyses may include testing published procedures, adapting published procedures, and establishing new procedures. Laboratory data obtained with any new procedure will need to be calibrated and correlated to changes in soil test level and/or crop response in incubation, greenhouse, or field studies. Data from these studies will be used to improve nutrient recommendations. Research techniques for objective 3 include field evaluation of various methods/materials that seek to increase soil nutrient availability by measuring changes in soil test levels, tissue nutrient concentrations, and crop yield. Additional laboratory research may include techniques to quantify changes in nutrient availability in a controlled environment which cannot be measured in the field. These analyses might include changes in dissolved organic carbon, speciation of organic acids, and dissolved iron, aluminum, and calcium concentrations all of which may impact soil nutrient availability.

Progress 10/01/04 to 09/30/11

Outputs
OUTPUTS: A wide variety of research was accomplished under this umbrella of Soils Research. The overall goal of the research program in 2009 was to elucidate the nutrient needs and nutrient use efficiency of field and forage crops, along with the cycling of nutrients in soils. Research conducted over the past year included: 1) Potassium fertilizer requirement for corn and soybean and soil test potassium drawdown; 2) Comparison of the nitrogen use efficiency and nitrogen needs of corn hybrids with and without transgenic corn rootworm resistance; 3) Maximizing nitrogen use efficiency, yield, and quality of grass pasture through the use of nitrogen fertilizer technologies; 4) Understanding plant availability of manganese in glyphosate resistant soybean systems; 5) Effect of dairy manure application timing and incorporation on nitrogen availability and ammonia emissions; 6) Evaluate the effectiveness of lime type (pell lime vs. traditional ag lime) and tillage system (notill vs chisel) on increasing soil pH with depth and crop yield; 7) Survey the adequacy of alfalfa nutritional status in Wisconsin as measured by in-season plant anlysis. 8) Effect of nitrogen fertilizer application timing and use of nitrification inhibitors on corn yield, nitrogen use efficiency, and profitable returns to fertilizer investment. Field and laboratory studies were completed to meet each individual project's objective. Data analysis is on going. Results are being added to the University of Wisconsin soil fertility databases and used to revise/create nutrient management decision making tools and best management practices. Research results were disseminated to target audiences at the Wisconsin Crop Management Conference; the Soil, Water, and Nutrient Management Meetings; Fluid Fertilizer Forum; numerous field days and County Extension meetings; crop management conferences in other states; Wisconsin Crop Manager Newsletter, Agri-view. In 2010, over 5,000 people have received information that was derived in whole or part from this research program. PARTICIPANTS: PI (1)- Supervised research, assisted plot establishment, reported results, extended results to clientele. Graduate Research Assistant (1) - conducted the laboratory and field research, responsible for sample collection and analysis, and supervised undergraduate student hourly Undergraduate Student hourly worker. (2) - assisted graduate student with sampling and analysis. Technical staff (2) - assisted in plot maintenance. Portions of this research were supported by the Wisconsin Fertilizer Research Council, Fluid Fertilizer Foundation, Wisconsin Soybean Marketing Board, Wisconsin Corn Promotion Board; Aglime research funds. Additional partners in this research are Dow Chemical and Agrotain. TARGET AUDIENCES: The target audience for information generated by this research are: 1) regulatory personnel who will use information to make decisions on nutrient management regulations; 2) agronomists who write farm nutrient management plans and/or advise farmers on fertilizer/nutrient applications; 3) farmers who are responsible for applying nutrients in a manner that complies with regulations and that maximizes farm profitability; and 4) other researchers who may find this information useful. PROJECT MODIFICATIONS: Not relevant to this project.

Impacts
Key results from project research found: 1) Soil test levels and soil type effect the amount of potassium that is fixed or released overwineter. 2) Corn hybrids with corn rootworm resistance do not appear to have different nitrogen needs than non-transgenic hybrids. Nitrogen use efficiency in a given corn hybrid varies from year to year. 3) When adequate rainfall occurs and there is little nitrogen loss, various nitrogen fertilizer technologies result in similar total season long yield of grass pasture. However, timing of N application affects when maximal yield occurs and suggests that growers can manage grass production with nitrogen timing. 4) Glyphosate did not appear to reduce manganese availability to soybean and no yield response to manganese applied as starter and/or foliar was observed even though tissues manganese concentrations at early flower were low. 5) Incorporating manure more than one day after spring preplant broadcast application resulted in reduced corn yield and nitrogen use efficiency compared to broadcasting and incorporating within in one days time or injection of spring preplant manure. Sidedressing manure resulted in reduced corn yields and nitrogen use efficiency compared to preplant applications. Pelletized lime was more effective than an aglime for adjusting the pH in no-till over 18 months. However, there was no effect soybean or establishment year alfalfa yield. Potassium and sulfur were found to be deficient in 51% and 64% of surveyed alfalfa fields (39 samples from 19 counties) and suggest that growers should pay more attention to these two nutrients for profitable alfalfa production. In a growing season with a wetter than average June and July, sidedress applications of nitrogen fertilizer were more efficient than preplant applications on a deep well drained soils. The use of a nitrification inhibitor with preplant nitrogen applications increased yield but not significantly. The profitability of nitrification inhibitor needs to be evaluated because reducing denitrification losses reduces agricultures contribution to greenhouse gas (nitrous oxide) emission. Results of this research have been used to provide guidance to agronomists and farmers to assist in making fertilizer management decisions at a time when fertilizer prices were very high and the overall farm economy in Wisconsin was very poor. As the most appropriate rate of fertilizer is selected for a given situation, a farm's overall profitability increases. An additional benefit is that reducing over application of nitrogen reduces the potential for water quality degradation.

Publications

  • Vitko, L.F. 2010. Field and laboratory investigations of potassium dynamics in Wisconsin soils. M.S. Thesis. University of Wisconsin-Madison.


Progress 01/01/09 to 12/31/09

Outputs
OUTPUTS: A wide variety of research was accomplished under this umbrella of Soils Research. The overall goal of the research program in 2009 was to elucidate the nutrient needs and nutrient use efficiency of field and forage crops, along with the cycling of nutrients in soils. Research conducted over the past year included: 1) Potassium fertilizer requirement for corn and soybean and soil test potassium drawdown; 2) Investigation of potassium buffer capacities of Wisconsin soils; 3) Comparison of the nitrogen use efficiency and nitrogen needs of corn hybrids with and without transgenic corn rootworm resistance; 4) Maximizing nitrogen use efficiency, yield, and quality of grass pasture through the use of nitrogen fertilizer technologies; 5) Understanding plant availability of manganese in glyphosate resistant soybean systems; 6) Survey of the fertility of subsoils in Wisconsin; 7) Effect of dairy manure application timing and incorporation on nitrogen availability and ammonia emissions; 8) Evaluate the effectiveness of lime type (pell lime vs. traditional ag lime) and tillage system (notill vs chisel) on increasing soil pH with depth and crop yield. Field and laboratory studies were completed to meet each individual project's objective. Data analysis is on going. Results are being added to the University of Wisconsin soil fertility databases and used to revise/create nutrient management decision making tools and best management practices. Research results were disseminated to target audiences at the Wisconsin Crop Management Conference; the Soil, Water, and Nutrient Management Meetings; the North Central Extension-Industry Soil Fertility Conference; numerous field days and County Extension meetings; and Crop and Soils Magazine. In 2009, over 5,000 people have received information that was derived in whole or part from this research program. PARTICIPANTS: PI (1)- Supervised research, assisted plot establishment, reported results, extended results to clientele Graduate Research Assistant (1) - conducted the laboratory and field research, responsible for sample collection and analysis, and supervised undergraduate student hourly; Undergraduate Student hourly worker (2) - assisted graduate student with sampling and analysis Technical staff (2) - assisted in plot maintenance Portions of this research were funded by the Wisconsin Fertilizer Research Council, Fluid Fertilizer Foundation, Wisconsin Soybean Marketing Board, and Wisconsin Corn Promotion Board. Additional partners in this research are Dow Chemical, Agrotain, and Agrium. TARGET AUDIENCES: The target audience for information generated by this research are: 1) regulatory personnel who will use information to make decisions on nutrient management regulations; 2) agronomists who write farm nutrient management plans; 3) farmers who are responsible for applying nutrients in a manner that complies with regulations and that maximizes farm profitability; and 4) other researchers who may find this information useful. PROJECT MODIFICATIONS: Not relevant to this project.

Impacts
Key results from project research found: 1) Exchangeable soil potassium levels are influenced by soil moisture content, the type of extractant used, and soil type. 2) Corn hybrids with corn rootworm resistance do not appear to have different nitrogen needs than non-transgenic hybrids. 3) When adequate rainfall occurs and there is little nitrogen loss, various nitrogen fertilizer technologies result in similar total season long yield of grass pasture. However, timing of N application affects when maximal yield occurs and suggests that growers can manage grass production with nitrogen timing. 4) Glyphosate did not appear to reduce manganese availability to soybean and no yield response to manganese applied as starter and/or foliar was observed even though tissues manganese concentrations at early flower were low. 5) Subsoil potassium fertility has decreased in two long-term rotation studies (18 and 44 years) while subsoil phosphorus has remained relatively stable over the same time period. Results of this research have been used to provide guidance to agronomists and farmers to assist in making fertilizer management decisions at a time when fertilizer prices were very high and the overall farm economy in Wisconsin was very poor. As the most appropriate rate of fertilizer is selected for a given situation, a farm's overall profitability increases. An additional benefit is that reducing over application of nitrogen reduces the potential for water quality degradation.

Publications

  • Sneller, E.G. and C.A.M. Laboski. 2009. P source effects on corn utilization and changes in soil test. Agron. J. 101:663-670.


Progress 01/01/08 to 12/31/08

Outputs
OUTPUTS: A wide variety of research was accomplished under this umbrella of Soils Research. The overall goal of the research program in 2008 was to elucidate the nutrient needs and nutrient use efficiency of field, forage, and potato crops, along with the cycling of nutrients in soils. Research conducted over the past year included: 1) Potassium fertilizer requirement for corn and soybean and soil test potassium drawdown; 2) Investigation of potassium buffer capacities of Wisconsin soils; 3) Comparison of the nitrogen use efficiency and nitrogen needs of corn hybrids with and without transgenic corn rootworm resistance; 4) Maximizing nitrogen use efficiency, yield, and quality of grass pasture through the use of nitrogen fertilizer technologies; 5) Understanding plant availability of manganese in glyphosate resistant soybean systems; 6) Investigation of the phosphorus requirement of potato and leaching potential in the Central Sands. Field and laboratory studies were completed to meet each individual project's objective. Data analysis is on going. Results are being added to the University of Wisconsin soil fertility databases and used to revise/create nutrient management decision making tools and best management practices. Research results were disseminated to target audiences at the Wisconsin Fertilizer, Aglime, and Pest Management Conference; the Soil, Water, and Nutrient Management Meetings; the North Central Extension-Industry Soil Fertility Conference; numerous field days and County Extension meetings; Crop and Soils Magazine; and The Badger CommonTater. PARTICIPANTS: PI (1)- Supervised research, assisted plot establishment, reported results, extended results to clientele Graduate Research Assistant (2) - conducted the laboratory and field research, responsible for sample collection and analysis, and supervised undergraduate student hourly Undergraduate Student hourly worker (1) - assisted graduate student with sampling and analysis Technical staff (2) - assisted in plot maintenance Portions of this research were funded by the Wisconsin Fertilizer Research Council, Wisconsin Potato and Vegetable Growers Association, Fluid Fertilizer Foundation, Wisconsin Soybean Marketing Board. Additional partners in this research are Dow Chemical, Agrotain, Specialty Fertilizer Products, and Agrium. TARGET AUDIENCES: The target audience for information generated by this research are: 1) regulatory personnel who will use information to make decisions on nutrient management regulations; 2) agronomists who write farm nutrient management plans; 3) farmers who are responsible for applying nutrients in a manner that complies with regulations and that maximizes farm profitability; and 4) other researchers who may find this information useful. PROJECT MODIFICATIONS: Not relevant to this project.

Impacts
Key results from project research found: 1) Soil potassium buffer capacities and drawdown of soil test levels vary by soil type. 2) Reducing nitrogen application rates for corn based on University of Wisconsin guidelines results in increased profitability. 3) Corn hybrids with corn rootworm resistance do not appear to have different nitrogen needs than non-transgenic hybrids. 4) When adequate rainfall occurs and there is little nitrogen loss, various nitrogen fertilizer technologies result in similar total season long yield of grass pasture. However, timing of N application affects when maximal yield occurs and suggests that growers can manage grass production with nitrogen timing. 5) Using manganese in a starter fertilizer for soybean resulted in no yield increase when foliar manganese was applied though foliar manganese could increase yield when no starter fertilizer was applied. 6) An economic yield increase is occurs when phosphorus fertilizer is applied to potato as starter fertilizer at rates not exceeding crop removal. These yield increases occur even when soil test phosphorus levels are very high (greater than 50 ppm). 7) Laboratory results show that phosphorus may leach on soils of the Central Sands with elevated soil test phosphorus levels even when no additional phosphorus is applied. In light of record high fertilizer prices, the results have proven timely in providing information to farmers and agronomists regarding the most economically advantageous nutrient application rates and best management strategies. Some farms have begun to reduce nitrogen application rates on corn and phosphorus on potato to improve economic profitability. An additional benefit, is that every pound of nitrogen and phosphorus fertilizer that is not applied and not needed, reduces the potential for water quality degradation.

Publications

  • Sweeney, A.E., K.A. Renner, C. Laboski, and A. Davis. 2008. Effect of fertilizer nitrogen on weed emergence and growth. Weed Sci. 56:714-721. Laboski, C.A.M., J.E. Sawyer, D.T. Walters, L.G. Bundy, R.G. Hoeft, G.W. Randall, and T.W. Andraski. 2008. Evaluation of the Illinois soil nitrogen test in the North Central Region of the USA. Agron. J. 100:1070-1076. Repking, M.J. 2008. Investigation of phosphorus requirement of potato in Wisconsin and phosphorus leaching potential in the Central Sands. M.S. Thesis. University of Wisconsin-Madison. p. 105.


Progress 01/01/07 to 12/31/07

Outputs
OUTPUTS: Research results for the phosphorus (P) availability to potato project were presented to approximately 300 potato growers and processors, regulatory personnel, and crop advisors at Wisconsin's Annual Potato Meetings and at two Field Days. These presentations showed that P fertilizer applications can be reduced and yields maintained. PARTICIPANTS: PI (1)- Supervised research, assisted plot establishment, reported results, extended results to clientele; Graduate Research Assistant (1) - conducted the laboratory and field research, responsible for sample collection and analysis, and supervised undergraduate student hourly; Undergraduate Student hourly workers (2) - assisted graduate student with sampling and analysis; Technical staff (2) - assisted in plot maintenance; Research was funded by the Wisconsin Potato and Vegetable Growers Association and Wisconsin Fertilizer Research Council. TARGET AUDIENCES: Target audiences include: 1)regulatory personnel who will use information to make decisions on nutrient management regulation; 2)crop consultants and fertilizer dealers who write farm nutrient management plans; 3)farmers who are responsible for applying nutrients in a manner that complies with regulations; and 4)other researchers who may find this information useful.

Impacts
In 2007 research on phosphorus (P) availability to potato was continued. This is a multi-year study assessing the effect of P fertilizer and soil amendments on P availability to the potato crop and the yield obtained. For Russet Burbank, yield increases in 2006 when Avail+MAP was applied compared to TSP may have been caused by not comparing the exact same fertilizer materials. In 2007, when Avail+MAP was compared to MAP, yield increases were small and yield decreased at one location when Avail was applied. Avail had no significant effect on mean tuber size for Russet Burbank. Sidedress application of of P fertilizer was ineffective at increasing yield. For Frito Lay 1867, use of Avail resulted in increases and decreases in marketable yield compared to TSP or MAP. When Avail was applied with MAP compared to MAP or TSP alone, mean tuber size was smaller at three locations, though only significant at one location. Because this variety is grown for seed, a smaller tuber size is desirable. If Avail can consistently produce tubers with a somewhat smaller size, then the cost of Avail (approx. $5-7/a) may be an economical investment for seed potato growers. Marketable Russet Burbank tuber yield was maximized with application of 65 lb/a of phosphate on coarse-textured soils with soil test levels ranging from very low to excessively high. On silt loam soils, marketable Frito Lay 1867 yield was maximized with application of 65 lb/a of phosphate on high P testing soils and with application of 130 lb/a of phosphate on low and optimum P testing soils. A few key potato growers began to reduce phosphate fertilizer application rates by 30 to 50 lb/a. Successful crop production with lower rates will show other growers that they too can reduce rates thereby increasing profitability and reducing the potential for water quality degradation. If UWEX phosphorus fertilizer recommendations are confirmed through this research, most potato growers will be able to reduce their P fertilizer rate by approximately 30 lb/a. This translates into approximately $630,000 across the potato production areas in Wisconsin. Potassium deficiency and fluctuating soil test levels are becoming more prevalent in Wisconsin even though growers may be following UWEX fertilization guidelines. The study started in 2006 was continued in 2007 with plots being planted to soybean. There was no effect of soil test potassium level on soybean yield which was unexpected because soil test levels varied from very low to low, where a yield response is expected, to excessively high, where no yield response is expected. Soil sample analyses have not been completed. Until soil sample analysis is complete, further data analysis can not continue. Understanding soil K dynamics is important to ensure that UWEX fertilization guidelines are adequate for economically viable grain and silage production in Wisconsin. This is particularly important because farmers often apply to little potassium fertilizer and the price of fertilizer has increased 300% in the last five years.

Publications

  • Peters, J.B. and C.A.M. Laboski. 2007. Garden fertilization UWEX Pub A2304. p.4.
  • Laboski, C.A.M. 2007. Nutrient management for potato production: balancing long-term economic and environmental sustainability. CommonTater 59(4):10-12.
  • Laboski, C.A.M. and K.A.Kelling. 2007. Influence of fertilizer management and soil fertility on tuber specific gravity: A review. Am. J. Potato Res. 84:283-290.


Progress 01/01/06 to 12/31/06

Outputs
In 2006, research on phosphorus (P) availability to potato was continued. This is a multi-year study assessing the effect of P fertilizer and soil amendments on P availability to the potato crop and the yield obtained. While potato responds to additional fertilizer P at high soil test P levels, over application of P fertilizer has the potential to cause P leaching in sandy soils. Research was conducted at three locations in the Central sands, two locations in Langlade Co., and one location in Washburn Co. Generally data from all plots confirms the current UWEX P application rate guidelines. The benefits of using Avail coated monoammonium phosphate (MAP) are not entirely clear cut on optimum to high P testing soils. On low P testing soils, Avail coated MAP showed greater benefits. There was no clear benefit to sidedressing P compared to applying it in starter fertilizer. Overall, there was no advantage, and minimal, if any, disadvantage to using alfalfa or poultry pellets as a source of P. Tissue P concentrations on various sampling dates did not vary much with treatment and were generally not correlated to final yield achieved. A preliminary experiment was conducted to ascertain how deep within a soil profile elevated soil test P and water extractable P concentrations could be found. Additionally the effect of source water on P extractability was briefly studied. Preliminary findings suggest that water quality may impact the amount of P available to a crop, particularly in fields where irrigation may supply the majority of the water for a crop. Additional research will be conducted in 2007 at more field locations on different soil types/environments. Research will also follow up on the potential effects of water quality of P availability and potential for P leaching in sandy soils. Potassium deficiency and fluctuating soil test levels are becoming more prevalent in Wisconsin even though growers may be following UWEX fertilization guidelines. In 2006 a study was initiated to gain a better understanding of potassium (K) dynamics in the soil and subsequent impacts on fertilizer K requirement for corn and soybean. The specific objectives include: 1) Understand the impact of soil drying on soil test K (STK) levels for soils with different parent materials. 2) Quantify the seasonal variability in STK for different soils. 3) Assess the interactive effects of soil test extract type with soil drying on STK. 4) Reaffirm critical STK levels for corn and soybean production. 5) Validate K crop removal values that are currently used. Preliminary results show that there was a yield increase to applied potash at only one of the five locations. A yield response was expected at all locations, further analysis of the data is needed to understand these results. Soil sample analysis is ongoing. Very preliminary results suggest that analyzing samples that were moist, air dried or oven dried impacts the amount of extractable K and the influence varies by soil location implying that clay mineralogy is affecting the results.

Impacts
If UWEX phosphorus fertilizer recommendations are confirmed through this research, most potato growers will be able to reduce their P fertilizer rate by approximately 30 lb/a. This translates into approximately $630,000 across the potato production areas in Wisconsin. Reducing over application of P will reduce the potential for degradation of surface water quality and may reduce the probability of P migrating to ground water. More importantly it is imperative that potato growers have the ability to implement nutrient management plans that are protective of water quality and allow for economic viability of the farm operation. Understanding soil K dynamics is important to ensure that UWEX fertilization guidelines are adequate for economically viable grain and silage production in Wisconsin.

Publications

  • Laboski, C.A.M., J.B. Peters, L.G. Bundy. 2006. Nutrient application guidelines for field, vegetable, and fruit crops in Wisconsin. UWEX Publication A2809. pp. 70.


Progress 01/01/05 to 12/31/05

Outputs
In 2005 research on phosphorus (P) availability to potato was initiated. This is a multi-year study assessing the effect of P fertilizer and soil amendments on P availability to the potato crop and the yield obtained. While potato responds to additional fertilizer P at high soil test P levels, over application of P fertilizer has the potential to cause P leaching in sandy soils. Soil amendments such as green manures have the potential to improve availability of soil P. The objectives of this study were to: 1) Assess the response of potato yield and quality and tissue P concentrations to applications on various quantities in P in starter fertilizer. 2) Determine if in-season application of P can increase P in tissue and improve potato yield. 3) Determine if application of alfalfa pellets can increase P in tissue and improve potato yield. Research was conducted at Hancock ARS and at the Antigo Airport. Soil samples were collected to 6 inches in each plot and analyzed for Bray P. An incomplete factorial design was used for the treatments: P in starter fertilizer at rates of 0, 65 or 130 lb phosphate/a, with and without 2 T/a of alfalfa pellets, and with and without sidedressing 65 lb phosphate/a at first flower. Sidedress treatments were not applied to plots that had 130 lb phosphate/a in starter fertilizer. Russet Burbank potato was planted at both locations. There was no significant difference in total yield, yield of US No. 1 tubers, or specific gravity between treatments at Hancock. At Antigo, there was no difference in total yield or specific gravity between treatments. The effects of alfalfa pellets and sidedressing were similar for yield of US No. 1 tubers. Sidedressing may have increased the amount of P available to the crop shortly after application (first flower). The alfalfa pellets likely acted as a slow release P source that may have increased P availability in mid-season. Alfalfa pellets supplied a total of 25 lb phosphate/a, however the effect on yield was similar to 65 lb phosphate/a of sidedressed fertilizer P. Thus, it seems likely that the slow release nature of the pellets and/or the release of P bound to the soil caused by compounds in the pellets was adequate to increase yields. Additional research will be conducted in 2006 at more field locations on different soil types/environments in an effort to better understand the results of 2005. Laboratory research will also be conducted as a means to understand how P and carbon sources along with soil type and irrigation water quality affect P availability to the potato crop. In 2005 proposals were written to obtain funding for new research. The objectives of the proposed study are to gain a better understanding of K dynamics in the soil and subsequent impacts on fertilizer K requirement for corn and soybean for improved economic viability of crop production in Wisconsin.

Impacts
If University of Wisconsin phosphorus fertilizer recommendations are confirmed through this research, most potato growers will be able to reduce their P fertilizer rate by approximately 30 lb/a. This translates into approximately $630,000 per year across the potato production areas in Wisconsin. Reducing over application of P will reduce the potential for degradation of surface water quality and may reduce the probability of P migrating to ground water. More importantly it is imperative that potato growers have the ability to implement nutrient management plans that are protective of water quality and allow for economic viability of the farm operation.

Publications

  • Withers, P.J.A., D.M. Nash, and C.A.M. Laboski. 2005. Environmental management of phosphorus fertilizers, pp. 781-828, Chapt. 25. In Sims, J.T., A.N. Sharpley, G.M. Pierzynski, D.T. Westermann, M.L. Cabrera, J.M. Powell, T.C. Daniel, and P.J.A. Withers. (eds) Phosphorus: Agriculture and the Environment. Agronomy Monograph 46. ASA-CSSA-SSSA. Madison, WI.