Download presentation
Presentation is loading. Please wait.
Published byTavion Enderby Modified over 10 years ago
1
Phosphorus Indices: an Understanding of Upper Mississippi Strategies John A. Lory, Ph.D. Division of Plant Sciences University of Missouri
2
Outline Overview Phosphorus indexes: why do we need them? Does it make sense that every state is different? Missouri P index Our objectives. What you need to make it work.
3
Many streams and lakes are phosphorus limited. Jones and Knowlton 1993 Water Clarity as measured by Secchi depth (m) Missouri reservoirs
4
Challenge: Where, when, and how to apply manure to minimize P loss to surface water.
5
Runoff volume Method of application Time since application Application rate Soil test P Soil type Cultivation Vegetative cover Factors affecting runoff of P
6
Nutrient planners are required to assess phosphorus loss on all fields receiving manure.
7
You choose the method Agronomic soil test recommendation Objective: does the crop need P? Phosphorus threshold Phosphorus Index Objective: will applied P be vulnerable to losses?
8
Low N-based Applications Medium N-based Applications High P-based Applications Very High No Manure Applications Phosphorus Assessment
9
Assessment tools are state specific. Index Target: - Runoff - Irrigation - Runoff - Irrigation Long-term Runoff - Runoff - Leaching
10
Assessment tools are state specific. Approach: Multiplicative tabular factors Simplified model Additive tabular factors Simplified model
11
Do Differences Between States Make Sense?
12
Missouri’s approach: 2 choices Agronomic soil test recommendation Objective: does the crop need P? Phosphorus threshold Phosphorus Index Objective: will applied P be vulnerable to losses?
13
Missouri P index objectives Strategic planning tool for use in writing a 5-year nutrient management plan. Identify fields where field characteristics are likely to result in high P loss in runoff. Simple to use with readily available information for people with an NRCS conservation plan.
14
6 Factors in the Missouri P index Soil test result include units and sampling depth Tillage Tilled vs. notill and forages RUSLE estimate of erosion Land cover Soil hydrologic group A, B, C or D Distance from water feature
15
Simple model approach Sediment P Function of RUSLE-2 erosion, soil test P and sediment delivery ratio. Soluble P Function of runoff volume (curve number approach and soil test P).
16
Higher standard in the clear-water region of the state.
17
P index rating system RatingClear-water region Other Low<1 <3 Medium>1 and 3 and <7 High>5 and 7 and <12 Very High>10 >12
18
6 Factors in the Missouri P index Soil test result include units and sampling depth Tillage Tilled vs. notill and forages RUSLE estimate of erosion Land cover Soil hydrologic group A, B, C or D Distance from water feature
19
Surface applications require a tactical tool. Educational tools being developed to identify times of year runoff least likely Inputs: Ground cover- County Soil hydrologic group- Soil condition Soil moisture Output Evaluation of runoff risk (low, medium, high) Predicted rainfall amount needed to initiate runoff
20
P index developed cooperatively by MU and NRCS. Based on best professional judgment. Available as a spreadsheet at: http://nmplanner.missouri.edu/
21
Future P index integrated into RUSLE 2 Email notification system to help evaluate timing of manure applications.
Similar presentations
© 2025 SlidePlayer.com. Inc.
All rights reserved.