Introducing a New Soil Test Methodology to Determine Nitrogen Fertilizer Rates. Introduction

Transcription

1 Introducing a New Soil Test Methodology to Determine Nitrogen Fertilizer Rates Rick Haney and Daren Harmel Introduction Current environmental issues Excessive nutrients in water degrade ecological function increase water treatment costs diminish recreational opportunities Current agro-economic climate Difficult time for farmers and ranchers high costs of inputs, equipment, land steady commodity prices increased regulatory pressure (current and future) 1

2 Nutrient sources Introduction Agricultural and urban fertilization Land application of animal by-products Waste water treatment plants Septic systems, sewer lines Natural/background New strategy needed to reduce input of N fertilizer from agriculture into US waters Traditional Strategy Fertilizer N application rates typically based on: Unrealistic yield goals (maximum yields) Conventional soil test methods -or- recent history -or- fertilizer dealer recommendations Production goal = maximize yield Fertilizer vs. rain Over application of N often results Contributes to water quality problems Limits on-farm profitability 2

3 New Strategy Fertilizer N application rates based on: Realistic yield goals (average yields) Enhanced soil test method Production goal = maximize profit Fertilizer vs. rain This strategy optimizes fertilizer rates such that N needs are met for actual growing conditions reduces N runoff and leaching maximizes on-farm profitability only needed fertilizer applied, which reduces input costs and lessens risk Enhanced Soil Test Method Enhanced Soil Test Method Accounts for all sources of plant available N NO 3 -N NH 4 -N mineralizable organic N Conventional Soil Test Methods Only account for NO 3 -N 3

4 Enhanced Soil Test Method Mineralizable organic N This important nutrient source is not directly considered in traditional soil test fertilizer recommendations. Microbes provide plant available N in the form of NH 4 -N and NO 3 -N when they break down (mineralize) soil organic matter Haney et al. (2000, 2004, 2008) developed methods to quickly and accurately quantify microbial activity (CO2 released) and relate it to the amount of N released as NH 4 -N and NO 3 -N. Enhanced Soil Test Method 120 Plant available N lbs/ac hour CO 2 4

5 Enhanced Soil Test Method N forms and values in Central Texas soils NO 3 -N average 20 lb/ac = $12/ac NH 4 -N average 7 lb/ac = $4/ac Mineralizable organic N average 10 lb/ac = $6/ac Simply accounting for all sources of plant available N can save substantial $$$ *Value based on $256/ton , Belton Feed & Supply, Aug. 25, 2009 Method Evaluation Research and demonstration project Efficient Nitrogen Fertilization: Accounting for Field Nitrogen Mineralization Funded by: USDA-ARS 319(h) grant from Texas State Soil and Water Conservation Board and USEPA Region 6 5

6 Method Evaluation Established demonstration sites in seven Texas counties Method Evaluation At each demonstration site, established 3 fields Fields were managed the same except for fertilizer 1 field received Enhanced Soil Test recommendations 1 field fertilized based on landowner preference 1 field not fertilized control no fertilizer ARS 70 lb N/ac 20 lb P 2 O 5 /ac traditional 100 lb N/ac 20 lb P 2 O 5 /ac 6

7 Method Evaluation For each field Collected soil sample prior to planting determined fertilizer rate with Enhanced Soil Test method Collected data on: fertilizer rate, cost crop yield control no fertilizer ARS 70 lb N/ac 20 lb P 2 O 5 /ac traditional 100 lb N/ac 20 lb P 2 O 5 /ac profit ( throughput = revenue fertilizer cost) water quality data (at USDA-ARS Riesel Watersheds) Compared results for, wheat/oats, sorghum Water Quality 7

8 Results Wheat/Oats yield (bu/ac) control ARS traditional Results Wheat/Oats 30 N rate (lb/ac) control ARS traditional 8

9 Results profit throughput ($/ac) Wheat/Oats 0 control ARS traditional Conclusions Critical to carefully manage fertilizer inputs to Maximize and sustain profitability Minimize contribution to water quality degradation **Difficult to convince farmers to change their approach to fertilizer use** This Enhanced Soil Test Method determines the total amount of plant available N in the soil Allows farmer to apply the correct amount of fertilizer to meet any N deficiency for a reasonable yield goal (production level) Also includes methods for plant available P determination 9

10 Questions??? To send soil samples: Dr. Rick Haney USDA-ARS 808 East Blackland Rd. Temple, TX For simple answers: Daren Harmel For better answers: Rick Haney