Fertiliser Use Phil Humphrey

Transcription

1 Fertiliser Use Phil Humphrey Name Name - Date year (click your master to change)

2 What is the Farming Advice Service? Basically an extension of the Cross Compliance Advice Service Funded by Defra, Managed by AEA (with tech input from ADAS) Delivered by a selection of local consultants & advisers Advice is funded to be delivered on the following subject areas:- - Cross Compliance - Nutrient Management - Climate Change - Competitiveness

3 Introduction This talk will cover the following:- 1. Some Basic principles regarding Fertiliser planning. 2. Understanding the jargon associated with nitrogen planning. 3. A brief guide to how nitrogen fertilisers work and how to manage different types of nitrogen.

4 Some Basic Principles Crop yield is usually limited by a series of limiting factors throughout the period from sowing to maturity and harvest. The most limiting factor at any given time can be regarded as the Click first to limiting edit factor. Master title style First limiting factors are not always nutrition and are not always obvious!

5 Some Basic Principles Some common limiting factors in combinable crop production are:- Poor drainage and/or soil structure. This leads to water-logging or susceptibility to drought. Poor soil ph, leading to poorer access to and utilisation of soil nutrients. Manganese deficiency The most common trace element deficiency locally, but easy to spot and stop!

6 Some Basic Principles Targets for soil nutritient status P index of 2 (16-25 mg/litre) K index of 2- ( mg/litre) Click Mg index to edit of 1 (26-50mg/litre) Master title style ph 6.5 for arable crops, or 6 for long term grassland. Remember sulphur, especially for OSR, 2 nd Wheat and grassland that is mainly cut. Note K releasing clays V light soils for inputs of K fertilisers. Remember not just N, but P, K and sulphur etc. value of manures.

7 Typical Values for some Organic Manures

8 Using Nitrogen some jargon Soil Mineral Nitrogen (SMN) = the amount of nitrogen in a crop available form within the rooting zone of a crop. Soil Nitrogen Supply (SNS) = SMN + N that the crop has already taken up + an estimate of likely additional conversion of N in the soil to N that a crop can use within its growing period before application of any fertiliser. This is a necessary figure to have as part of a nitrogen plan. Total Nitrogen = the total quantity of nitrogen a fertiliser product contains (fertiliser products can include manure, slurry, compost etc.) Available Nitrogen = The % of the Total Nitrogen that can be expected to be used by the crop the fertiliser product is applied to. For manufactured N fertilisers, this will be the same as the %N quoted as being in the product.

9 Available & Total N in some Manures Pig slurry Cattle slurry Slurry High available N Click to edit Master Broiler litter title style Layer manure Poultry Manures High available N FYM Low available N 'Old' FYM Ammonium-N Uric acid-n Organic N 'Fresh' FYM

10 Using Nitrogen some more jargon Nitrogen Use efficiency (of manures or slurries) = The % of the Total N that can be regarded as available N to the crop to which the product is applied. Efficiency of Crop Uptake = the % of the potentially available nitrogen from either the soil or fertiliser products applied that actually gets taken up by a crop. For manufactured fertilisers this figure is usually expected to be around 60% (55% on shallow soils or up to 70% on sandy soils). Apparent Utilisation Efficiency (often expressed as a %) = N content of crop yield + fert. - N content of crop yield with no fert. kg/ha of N applied

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12 NVZ Compliance N max & manures

13 N Efficiency of organic manures in NVZs Manure Type Application time % available NVZ Likely real % available Potential fertilser gap (kg/ha) FYM Autumn Cattle Slurry Autumn Cattle Slurry Spring Pig Slurry Autumn Pig Slurry Spring Poultry Manure Autumn

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16 What type of Nitrogen to Use? Main debate is Urea V Ammonium Nitrate. Supporting one over the other has developed into a national commercial sport! Both have high energy costs and pollution risks, so need to be used with due respect. Urea + side, more resistant to nitrate leaching losses. - side, higher risk of loss of N as ammonia gas into atmosphere and leaching of Urea-N. Ammonium Nitrate + side, low risk of high levels of ammonia loss. - side, higher risk of nitrous oxide pollution and nitrate leaching losses if wet at application Mitigating nitrate leaching is the focus of NVZs. (Refs. Defra, NT2605, WP1a,1b,WP2 & WP4 reports 2005/06)

17 Nitrous Oxide Emissions

18 Changes in Nitrous Oxide Emissions

19 Ammonium Nitrate & Urea Ammonium Nitrate = Nitric Acid (HNO 3 ) + Ammonia (NH 3 ) NH 4 NO 3 Urea = Carbon Dioxide (CO 2 ) + Ammonia (2NH 3 ) CO(NH 2 ) 2 + H 2 O

20 An Example of Manufacturing Progress Reductions in the energy used to manufacture ammonia Source:- (Indian Farmer Fertiliser Co-operative)

21 Urease Inhibitors Urea + Moisture = Carbon Dioxide + Ammonia Chemical reaction = (NH2)2CO + H20 CO2 + 2NH3 Urease is an enzyme that catalyzes this reaction. When soil is dry, Click Ammonia to edit gas volatises Master into title the air. style If wet, it converts to Ammonium-N (NH4-) in the soil which binds to soil particles. Agrotain is a common example of an inhibitor product. (eg Koch Advanced Nitrogen) based on nbtpt = N-(n-butyl) thiophosphoric triamide. High soil temperatures at application and high soil ph also increase the risk of losses as ammonia

22 The Nitrogen Cycle Yellow arrows indicate human sources of nitrogen to the environment. Red arrows indicate microbial transformations of nitrogen. Blue arrows indicate physical forces acting on nitrogen. Green arrows indicate natural, non-microbial processes affecting the form and fate of nitrogen.

23 Nitrification Inhibitors Slow down the conversion of Urea & Ammonium-N to Nitrites and Nitrates. Didin (dicyandiamide or DCD) is a common example

24 Other ways to enhance nitrogen fertilisers 1. Polymer coatings eg Nutrisphere-N 2. Spray on N fixing bacteria eg TwinN

25 Nitrate leaching from excess nitrogen

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27 Costing of Nutrients Always calculate costs on the basis of pence per kg of nutrient (not per tonne of product). For straight fertilisers: Cost (pence per kg) = Price per tonne ( ) x 10 % nutrient For compound fertilisers, manures, composts etc, calculate the cost of NPK in the straight fertilisers that could be used. Use these costs (pence per kg) to calculate an equivalent cost of the compound compared to the same nutrients applied as straights.

28 Break Even Ratio (BER) BER = cost of nutrient (p/kg) Click to value edit Master of produce title style (p/kg)

29 BER example 34.5% 275 / t = 275 X 100 = 80 p/kg 34.5 X /t = 150 X 100 = 15 p/kg = BER of 5.3 : 1 15

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