RELATIONSHIP OF ORGANIC PHOSPHORUS BIOAVAILABILITY AND PH TO PLANT GROWTH, PHOSPHORUS UPTAKE, AND MYCORRHIZAL ESTABLISHMENT

• Sponsoring Institution: National Institute of Food and Agriculture
• Project Status: COMPLETE
• Funding Source: HATCH
• Reporting Frequency: Annual
• Accession No.: 0192056
• Project Start Date: May 1, 2002
• Project End Date: Nov 30, 2007
• Program Code: [(N/A)]- (N/A)

Recipient Organization
UNIVERSITY OF NEBRASKA
(N/A)
LINCOLN,NE 68583

Performing Department
AGRONOMY & HORTICULTURE

Non Technical Summary
Management-induced surface and subsurface soil acidity (i.e., long-term N fertilization) is a potential threat to sustainable production and yield potential. The causes threatening production may be associated with toxic levels of Al and Mn, or due to depletion or unavailability of P and other essential nutrients. This research will attempt to understand how soil acidity affects soil solution chemistry, P uptake, and mycorrhizal infection/colonization.

Animal Health Component

25%

Research Effort Categories

Basic

75%

Applied

25%

Developmental

(N/A)

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
102	0110	1060	30%
102	0110	2000	50%
102	5210	2000	20%

Knowledge Area
102 - Soil, Plant, Water, Nutrient Relationships;

Subject Of Investigation
0110 - Soil; 5210 - Fertilizers;

Field Of Science
1060 - Biology (whole systems); 2000 - Chemistry;

Keywords

acidity

soil properties

liming

mycorrhizae

organic compounds

phosphorus

aluminum

toxicity

manganese

nutrient availability

soil ph

plant growth

nutrient uptake (plants)

soil plant nutrient relations

soil chemistry

fertilizers

irrigation management

soil management

management systems

sandy soils

environmental factors

rhizosphere

quantitative analysis

corn

soybeans

cropping systems

soil analysis

application rate

crop yields

data bases

Goals / Objectives
1. To assess the dominant cause(s) of surface and subsurface soil acidity under irrigated and conservation management systems of northeast Nebraska. The working hypothesis of this objective is that the extent and severity of soil acidity under irrigated systems on low buffering capacity sandy soils is dependent on management factors, inputs, and soil properties. 2. To determine the bioavailability of common (in soil and manure) organic P compounds for plant uptake at various organic/inorganic P ratios and pH. The working hypothesis of this objective is that the affinity of plants to uptake organic P is dependent on the ratio of organic/inorganic P and the chemical environment (as controlled by pH) of rhizosphere. The degree of hydrolysis depends on the structure of organic Po species and the pH. 3. To quantify corn, soybean, and mycorrhizae responses to pH-induced restricting elements in acidified sandy soil of northeastern Nebraska. The working hypothesis of this objective is that acidification of subsurface soil in Nebraska has resulted in Al and/or Mn levels that restrict root growth thus ensuing in poor P uptake even when P is well supplied. 4. To mitigate surface and subsurface soil acidity using different strategies and modes of application of agricultural lime for conservation and conventional soil management systems and improve P uptake efficiency. The working hypothesis of this objective is that efficacy of liming material to remediate soil acidity and P uptake depends on source (i.e., various liming materials) and characteristic of liming and ability of liming to reach subsoil.

Project Methods
The objective of this first experiment is to assess the predominant cause(s) of surface and subsurface soil acidity under irrigated and conservation management systems of northeast Nebraska. The working hypothesis of this objective is that there is high soil pH variability in the field due to management, landscape position, and parent materials. The survey will be on two major cropping systems, with two N fertilizer placement method, and three soil-landscape positions managed with conservation tillage system. Soil will be sampled to a depth of 30-cm at depth increment of 8-cm. Soil samples will be analyzed for pH, extractable aluminum and manganese and lime requirement. In addition to the management history and fertilizer type, relevant information such as fertilizer rate, years of fertilizer application, and historic yield will be included in the database for each sampling site if available. The objective of this second experiment is to determine the bioavailability of common (in soil and manure) organic P compounds for plant uptake at various organic/inorganic P ratios and pH. The working hypothesis of this objective is that the affinity of plants to uptake organic P is dependent on the ratio of organic/inorganic P and the chemical environment (as controlled by pH) of rhizosphere. The experiment will be done in the greenhouse using sandy soils at various pHs. In this study, all essential nutrients (except P) as recommended by a soil test will be added to the soils. The recommended rate of P will be supplied at different ratios of inorganic and organic P. Corn and soybean, will each be grown in the soil and plant P uptake, uptake efficiency, root surface area, phosphatase activity, and mycorrhizal colonization will be measured. The objective of this third experiment is to quantify corn, soybean, and mycorrhizae responses to pH-induced restricting elements in acidified sandy soil. Soil collected from farmer's fields will be used to mimic the field soil acidification gradient and profiles of Al or Mn. Root surface area, above ground plant biomass, mycorrhizal development, soil solution chemistry, and nutrient uptake of corn and soybean grown on sandy soil will be measured. The objective of this fourth experiment is to mitigate surface and subsurface soil acidity using different strategies and modes of application of agricultural lime for conservation and conventional soil management systems. The working hypothesis of this objective is that efficacy of liming material to remediate soil acidity and P uptake depends on source (i.e., various liming materials) and characteristic of liming and ability of liming to reach subsoil. Soil collected from farmer's fields will be used to mimic the field soil acidification gradient and profiles of Al or Mn. The soil will be limed in three different strategies (no-till, reduced tillage, and conventional tillage). Root surface area, above ground plant biomass, mycorrhizal development, soil solution chemistry, and nutrient uptake of corn and soybean grown on sandy soil will be measured.

Progress 05/01/02 to 11/30/07

Outputs
OUTPUTS: Four presentations were given at professional meetings. In addition, two NebGuides were produced evaluating factors contributing to acidification and control measures of soil acidification. Dissemination through Presentations at National Meetings McCallister, D.L., D.T. Walters, M. Mamo, and R. Renken. 2001. Manure phosphorus concentration and cropping systems effects on soil phosphorus partitioning. American Society of Agronomy National Meeting, Charlotte, NC, October 21-26. McCallister, D.L., M. Mamo, D.T. Walters, and R. Renken. 2002. Manure Phosphorus Concentration and Its Effects on Soil Chemical and Depth Phosphorus Distribution. American Society of Agronomy National Meeting, Indianapolis, IN, Nov. 10-14. Mamo, M, C. Wortmann, C. Brubaker. 2003. Manure P fractions: Extraction methods and the effect of manure type. American Society of Agronomy National Meeting, Denver, CO, Nov. 2-6. Mamo, M, C. Wortmann, R. Renken. 2004. Phosphorus sorption in soils of Ethiopia, Uganda, and Mozambique. American Society of Agronomy National Meeting, Seattle, WA, Oct. 31-Nov. 4. PARTICIPANTS: Charles Wortmann, University of Nebrsaka, Lincoln Rhae Drijber, University of Nebrsaka, Lincoln Roger Renken, University of Nebrsaka, Lincoln Gregory Miller, Nunhems,Parma, Idaho Corey Brubaker, USDA-NRCS, Lincoln TARGET AUDIENCES: Farmers Crop Consultants Scientists

Impacts
State allocated graduate research assistantship supported a student for 2.5 years to complete a research project evaluating pH stratification effect on yield, P uptake, and root biomass. A thesis was successfully completed and a peer journal publication produced. The affect of pH on organic phosphorus was not conducted due to lack of success in acquiring federal funds to support the work. The summary of the soil pH affect on sorghum growth is described below. Soil acidity restricted root growth and biomass yield. Soil amendment in a band below the seed row greatly increased root growth below the layer of acidic soil for greatly increased capacity for uptake of nutrients and water. The increase in plant growth with band amendment of the acidic soil layer was less than with full amendment of the acidic layer, although the full amendment would require 3.4 times as much lime as band amendment.

Publications

• Greg Miller. 2006. Sorghum response to stratified soil pH and localized lime placement. MSc. thsis. Univ. of Nebraska, Dept. of Agronomy and Horticulture.
• Miller, G., M. Mamo, R. Drijber, C. Wortmann, and R. Renken. 2008. Sorghum growth, root responses, and soil solution aluminum and manganese in pH stratified sandy soil. Journal of Plant Nutrition and Soil Science. (In Press).
• Mamo, M., C. Wortmann, and S. Brubaker. 2007. Manure P Fractions: Analytical methods and the effect of manure types. Comm. Soil and Plant Anal. 38:935-947.
• Garcia, J.P., C.S. Wortmann, M. Mamo, R. A. Drijber, J.A. Quincke, and D. Tarkalson. 2007. One-time tillage of no-till: effects on nutrients, mycorrhizae, and phosphorus uptake. Agron. J. 99: 1093-1103. (MSc. co-advisor
• Wortmann, C., M. Mamo, and S. Shapiro. 2003. Management Strategies to Reduce the Rate of Soil Acidification. NebGuide G03-1503-A. University of Nebraska Cooperative Extension, Lincoln, NE.
• Mamo, M., C. Wortmann, C. Shapiro. 2003. Lime use for soil acidity management. NebGuide G03-1504-A. University of Nebraska Cooperative Extension, Lincoln, NE.

Progress 10/01/05 to 09/30/06

Outputs
Development of acidic soil is a long known by-product of production agriculture. A stratified sub surface layer of acidic soil can develop in minimally disturbed soil such as no till receiving injection of nitrogen fertilizer such as anhydrous ammonia. The objective of this study is to determine the effectiveness of band-applied lime in alleviating Al3+ and Mn2+ toxicities on sorghum yield and mycorrhizae. Soil columns 41 cm in length were packed with soil (Valentine fine sand mixed mesic Typic Ustipsamment and Thurman loamy sand mixed Mesic Udorhentic Haplustoll) with treatments applied at the 10 to18 cm depth to mimic soil pH stratification. The treatments at this depth were: 1) soil at pH of 3.7; 2) band lime application to pH of 5.8; 3) band lime application to pH of 6.3; and 4) conventional liming to pH of 5.8. The band treatment mimicked lime application to a section within the 10 to18 cm soil layer keeping the rest of the soil to pH 3.7. The soil above and below the 10 to18 cm depth was at pH 5.8. Sorghum (Sorghum bicolor L. Moench) was grown in the soil columns under controlled environment for six weeks. Toxic levels of Al3+ were found in soil at pH 3.7. Conventionally limed soil with pH of 5.8 throughout the soil columns produced significantly greater top growth, although all other pH or liming strategies performed better than the no lime or pH 3.7 treatment. The banded lime allowed roots to grow below the acidic layer of soil, but root growth was still significantly less than in the conventionally limed soils at pH 5.8. Mycorrhiza was able to grow equally well in the limed soil, but was significantly lower in the layer with pH 3.7, possibly due to Al3+ toxicity. It is recommended that more research be carried out to determine the effectiveness of banded lime applications in field conditions.

Impacts
Band lime application could allow preferential growth of roots and potential reduce the rate of lime needed to correct soil pH and aluminmum toxicity.

Publications

• Miller, Greg. 2006. Sorghum and mycorrhizal responses to liming strategies in pH stratified soil MSc. Thesis. University of Nebraska, Lincoln.

Progress 10/01/04 to 09/30/05

Outputs
This research will attempt to understand how soil acidity affects soil solution chemistry, P uptake, and mycorrhizal infection/colonization. The research is attempting to answer three hypotheses. Hypothesis 1-Localized lime application into a slot through the acidic layer will facilitate roots to grow through the acidic layer into the less acid subsurface soil to access water and nutrients. Hypothesis 2-Slot placement of lime in the acidic layer at different rates (to = pH 5.2 and 6.3) will not significantly increase sorghum performance. Hypothesis 3-Localized placement of lime in acidic layer will increase plant/mycorrhizal growth. An MSc. graduate student has completed experiments and is writing results. Thesis will be completed within the next 3 months.

Impacts
None to report

Publications

• No publications reported this period

Progress 10/01/03 to 09/30/04

Outputs
Long-term ammonium based N fertilizer use can lower the pH of a soil to the point where Al and Mn concentrations increase to toxic levels for plants. Whether the N fertilizer is surface applied, or injected into the soil, it is usually within the top 7 inches of the surface. Stratified acidification (distinct differences in pH as dependent on the depth in a soil) resulting from the fertilization can develop. Plant roots will potentially be unable to penetrate an extremely acidic layer because of the toxic nature of Al and Mn in soil solution. Arbuscular mycorrhizal (AM) fungi have a symbiotic relationship with plants that increase the plant potential for nutrient and water uptake. Little is known on how pH stratification affects the sorghum fungal relationship. Some argue that liming should be done to correspond with and rectify Al toxicity, otherwise making the soil non-toxic to a specific crop. The other and more traditional theory is that liming should be done to neutralize the pH, to bring the pH of the soil to a range of 6.5 to 7.0. We are conducting this experiment in soil columns in a greenhouse with soil collected from farmers fields. Within these soil columns we have packed soil to mimic different field conditions associated with stratified soil pH and liming practices. An acidic layer of soil is at the 10 to 18 cm depth with different liming treatments through it, representing the two theories of liming, as stated above. The limed areas are in the soil to represent a banded lime application. Our working hypotheses are: 1) Localized lime application into a slot through the acidic layer will facilitate roots to grow through the acidic layer into the less acid subsurface soil to access water and nutrients; 2) Slot placement of lime in the acidic layer at different rates (to pH 5.2 and 6.3) will not significantly change sorghum performance; 3) Localized placement of lime in acidic layer will increase plant/mycorrhizal growth. The objectives are: 1) To quantify the effect of amending a slot through an acidic soil layer on above ground and below ground biomass in sorghum grown in pH stratified soil columns; 2) To quantify the effect of amending a slot through an acidic soil layer on roots distribution and surface area of sorghum in pH stratified soil columns; 3) To quantify the effect of amending a slot through an acidic soil layer on N and P nutrient concentration and uptake in sorghum plants grown in pH stratified soil columns; 4) To measure the effect of amending a slot through an acidic soil layer on Al3+ concentration in soil and solution of pH stratified soil columns; 5) To quantify the effect of amending a slot through an acidic soil layer on Arbuscular Mycorrhizae on soil and roots at different soil depths through an extraction of Fatty Acid Methyl Esters (FAME). Both the soil and roots will be analyzed.

Impacts
None to report

Publications

• No publications reported this period

Progress 10/25/02 to 10/25/03

Outputs
A preliminary greenhouse experiment was carried out to study the availability of phosphorus to plants by manipulating the relative percentages of inorganic to organic P applied to the plant. A low P soil taken from a depth of about 10 cm was air dried, mixed and ground to pass through a 2-mm sieve. Each pot was filled with 2.4 kg of dry soil and saturated with water and allowed to stand to get to field capacity. 0.6 Kg of the soils were mixed with the treatment and placed as a layer on top of the soils in the pots. Each pot received blanket applications of ammonium nitrate (0.93 g) along with the treatments. The following amount of TSP and glucose-1-phosphate were applied: For the 100:1 ratio 0.34 g of ground TSP, 75:25 (0.25 g TSP and 0.17 g of glucose-1-Phosphate, 25:75 (0.0840 and 0.51) and 0: 100(0.68 g of glucose-1-phosphate), all these were applied based on fertilizer recommendation of 70 Kg per hectare of P2O5. Four sorghum seeds were planted in each pot and the seedlings were thinned out after one week. The shoot to root ratio was not significantly different among the treatments. The shoot to root ratio of the controls however was significantly greater than that of the other treatments. This is expected since P is needed for root development and a lack of P in the control pots resulted in poor root development. For the dry weight there were only significant differences between the control and the treatments but not among treatments. Soil and root mycorrhizae, enzyme activities and P fractions are being evaluated.

Impacts
None to report

Publications

• No publications reported this period

Progress 10/01/01 to 09/30/02

Outputs
Two sites have been selected based on soil textural class (coarse and fine texture) and P levels. These soils have low soil test P levels (< 7 ppm) and will be used to conduct greenhouse studies. In addition, a soil from northeastern Nebraska with stratified soil pH and Al levels has been collected. Preliminary experiments have been established in the greenhouse to evaluate the effect of organic to inorganic P ratios on corn P uptake, corn root characteristics, mycorrhizal infection, and soil P fractions. These results will help refine future laboratory and field experiments.

Impacts
At the completion of this study, it is expected that we will understand the relationship between soil acidity and the ability of mycorrhizae to infect roots. We expect that soil acidity will strongly influence root characteristics, which will in turn, impact the ability of mycorrhizae to thrive. The limited availability of mycorrhizae will coordinately reduce the bioavailability of phosphorus, due to decreased root-fungi interactions. These studies will help fine tune P management by improving P availability to plants and reducing loss of P to the environment.

Publications

• No publications reported this period