# Presentation: 717853

## N and P Management 

**N and P Management **

## Pasture Systems and Watershed Management Research Unit Mission 

**Conduct research leading to the development of land, water, plant, and animal management  systems, which insure the profitability and sustainability of northeastern grazing and cropping enterprises while maintaining the quality of ground and surface waters.**

## PSWMRU CRIS Projects

**Integrated Farming Systems**
**Grassland Ecology**
**Nutrient Management**

## Nutrient CRIS Objectives – Basic 

**Quantify P, N, and C cycling in soils impacted by fertilizer, manure, crop and grazing management**
**Develop methodology to link critical source areas and transport pathways of P and N by relating soil nutrient levels to losses in surface runoff and leachate and delineating hydrologic processes controlling nutrient loss from watersheds**

## Nutrient CRIS Objectives - Applied

**Develop and apply models and indices  to assess and rank site vulnerability to nutrient loss**
**P and N indices **
**Evaluate best management practices aimed at minimizing nutrient transfers from agricultural lands to water****.**
**P sequestering agents**
**Ash pavement **

## Forest

**Forest**

**Animal Agriculture**

**Grazing Lands**

**Croplands**

**Rural and Urban**** ****Communities**

##     Why the Concern ?

-   **Nitrates in ground waters**
**Health risk to infants **
**  ****Eutrophication**
**Algae & weed growth and blue-green toxins**
**Coarse fish numbers and fish kills**
**Chlorination of eutrophic drinking waters**
**carcinogenic risk.****  **

## Impacted Watersheds

**Chesapeake Bay**
**Watershed**

**New York City Watersheds **

## The Good Old Days !

**P**

**N**

**P**

**N**

**P**

**N**

**The Good Old Days !**

**Pre 1939 - N & P cycles were  sustainable**

## Today’s N & P Cycles are Fragmented

**Today’s N & P Cycles are Fragmented**

**P Rock**

**Manure N & P**

**Manure N & P**

**N Fertilizer**

## N-Based Manure Managementresults in excess P application

**N-Based Manure Management****results in excess P application**

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## N-Based Manure Management

**P added in manure exceeds crop removal**

## Farming System and P Balance

- Cash crop
- 30 ha

- 65 Holsteins
- 40 ha

**Farming System and P Balance**

- Pennsylvania farms

## P Accumulation is Localized w/in Farms!

- Dairy farm: 0.3 a.u./ha

- Barn

- Barn

## Soil Test P Survey, 1997

**30 - 50%**
**>50%**

**Soil Test P Survey, 1997**

- Percent of soils tested that had more P than crops need

## P Accumulates at Soil Surface

**P Accumulates at Soil Surface**

- Soil Test P, mg/kg

- Soil depth,
- cm

- Poultry litter added
- kg P/ha/yr for 10 years
- No manure
- 50 kg P/ha/yr
- 100 kg P/ha/yr

-   This is the zone that serves as the source of P to runoff!

## Runoff P Increases with soil P 

- Mehlich-3 soil P, mg/kg

- Dissolved P
- in runoff,
- mg/L

- Sandy loam

- Clay

- Loam

- Loam

- 0.5

- 0

- 1.5

- 1

- 2

- 0

- 200

- 400

- 600

## How much is too much?Agronomic and Environmental Thresholds

- Mehlich-3 soil P, mg/kg

- Dissolved P
- in runoff,
- mg/L

- 0.5

- 0

- 1.5

- 1

- 2

- 0

- 200

- 400

- 600

- 220

- 175

- 50

- Agronomic
- Environmental

## Excreted Dietary P 

**50-60%,~9 kg/6 months grazing**
**50-60%,~4 kg/6 months grazing **
**50-70%,~1 kg/6 months grazing**

## Fate of excreted P

**80% of P in inorganic form and available**
**Accumulates in surface soil**
**About 5% of area**
**Most susceptible to runoff **
**Accumulates in camping and feeding areas**
**Surface runoff can be high**
**Portion in feces increases with excess dietary P **

## P in Runoff 

- Area grazed

- Dissolved P  (mg L-1)

- 0

- 1.0

- 2

- 0.5

- 1.5

## Dietary P and Fecal P 

- Adapted Wu, Z. and V. Ishler, 2000.

- Dietary P (%)

- Fecal P (%)

## How Much Phosphorus feeding?

**How Much Phosphorus feeding?**

**What most dairy producers feed**

**0.3%**

**0.4%**

**0.5%**

**NRC Recommendation for >80 lb/d milk**

**Absolute waste!**

## Excreted Dietary N 

**75-80%, 30-120 kg/yr.**
**90-95%, 30-90 kg/yr.**
**85-95%,  5-25 kg/yr.**

## Excreted dietary N

**60% in urine, 40% in feces**
**But, on only about 15% of the pasture.**
**500 - 1000 kg N /ha rate under urine and fecal patches.**
**~20 % urine N leaches below root zone **
**Portion in urine increases with dietary N **

## Nitrate in Leachate 

**Nitrate in Leachate**** **

## Levels of Cooperative Work

**National**
**Project/Scientist level **
**Multi-laboratory/institution/agency**
** ****Mahantango Watershed**

## National P Research Project 

## National P Research Project 

## Project/scientist level cooperation

## Multi-laboratory/institution/agency cooperation

**MD eastern shore –  P sequestering, surface and subsurface P transport; coop with UMES and U Del**

## Mahantango Watershed Projects

**FD-36 – soil P-runoff P **
**relationships at watershed scale**

**Brown Watershed – runoff **
**generation processes**

**Ground water age dating – USGS**

**Pathogen transport – ARS-BARC**

**Mahantango Watershed Projects**

## N and P Sources and Pathways

**Subsurface**
**flow**

**Tile flow**

**N leaching large**
** ****P leaching**
**is small**

**N leaching**

**N leaching - most of watershed**

**P runoff -10% of watershed**

## The Critical Source Area Concept

## N and P Loss Factors

**N Loss**
**Transport**
**Soil texture**
**Soil permeability**
**Source**
**Fertilizer N**
**Manure N**

**P Loss**
**Transport**
**Soil erosion**
**Irrigation erosion**
**Runoff class**
**Contributing Distance**
**Source**
**Soil test P**
**Fertilizer P**
**Manure P**