Soil Testing for Nutrient Management on Vegetable Farms Becky Maden February 2018
What is Nutrient Management? Sufficient nutrients for maximum economic return Maximizing on-farm nutrient resources Minimizing nutrient loss to the environment Maintaining/improving soil physical, chemical, and biological properties
4 Rights of Nutrient Stewardship right right right right
Soil Sampling Basics
Steps of Soil Testing 1) Soil sampling 2) Soil analysis 3) Interpretation of results 4) Recommendations
To make a plan, you need to identify management ICF Rotation units on Blocks your farm
Soil Test Basics Uniform soil type Avoid abnormal areas Collect at least 10 samples Use a zig zag pattern
Soil Test Basics If possible, use a soil probe or augur. Sample 6-10 deep. Mix the soil sample in a bucket. Break up all clods and mix evenly. Pack ½ cup of evenly mixed soil in a plastic bag. Refrigerate until you mail/ deliver to lab.
Which test to use? Standard* (lab must use Modified Morgan Extract) Tests for ph, SOM, Macro and micro nutrients Nutrient management planning and first year high tunnels. UVM, UMAINE, UMASS, Dairy One PSNT (Pre Sidedress Nitrogen Test) Use just before normal sidedress time to determine if crop needs N. Long season crops that may need a nitrogen sidedress UVM, UMAINE, UMASS, Dairy One Tissue Sampling Use to determine deficiencies on longer season crops For perennial fruits or tunnel tomatoes UMAINE, UMASS, Dairy One SME (Saturated Media Extract) Tests for levels of available nutrients. For potting media or high tunnels UMAINE, UMASS.
Comparison of Soil Labs Lab--------> Waypoint Logan UVM ph 7.3 7.4 7.8 OM% 7.1 8.78 8.2 Sulfur 19 ppm 19 ppm 10 ppm Phosphorous 220 ppm* 398 ppm* 65.7 ppm Calcium 4859 ppm 2675 ppm 13795 ppm Magnesium 158 ppm 153 ppm 224 ppm Potassium 196 ppm 302 ppm 202 ppm Sodium 20 ppm 64 ppm 16 ppm
Soil Analysis Unavailable Available Increasing availability Melich 3 Bray Morgan
Soil Test Recommendations
Soil Analysis Soil Bank Minerals Organic Matter Colloids Stored nutrients ($avings account) Soil Solution Available nutrients (ATM)
Yield Soil Test Interpretation Critical soil test level Very Low Low Optimum Soil Test Level Above Optimum
P Interpretation example Relative yield of alfalfa in 31 Vermont soils with a range in soil test P (low to high). Critical soil test P = 4 ppm Magdoff et al., 1999. Soil Sci. Soc. Am. J. 63:999-1006
P interpretations for Modified Morgan (mg/kg or ppm) Very Low Low/ Below Optimum Medium Optimum Above Optimum Excessive MA all crops 0-2 2-4 4-14 14-40 > 40 CT Agronomic Crops 0-6.5 9-10 10-17.5 > 17.5 VT all crops 0-1.9 2-3.9 4-7.9 8-39.9 >40 ME established lawn 0-1.75 1.75-3.5 3.5-5 >5 ME potatoes 0-1.75 1.75-5 5-25 >25 SARE 'Building Soils for Better Crops' 0-2 2-4 4-7 7-20
Nitrogen use curves
Phases of broccoli crop nitrogen (N) uptake rate (lb/acre per day) and cumulative N uptake in lb/acre (1 lb/acre = 1.1209 kg ha 1 ) compared with broccoli biomass accumulation in ton/acre (1 ton/acre = 2.2417 mg ha 1 ) (Sullivan et al., 1999).
Questions?
Using Compost for Fertility Step 1: Get a soil test Step 2: Get a compost test Step 3: Determine crop nutrient needs Step 4: Do some math! Step 5: Get a soil test again next year
Step 2: get a compost test Vegetable Program
Step 3: Determine crop nutrient needs https://nevegetable.org/crops/cabbage-broccoli-cauliflower-and-other-brassica-crops Vegetable Program
Table 5: Approximate Nutrient Removal by Selected Vegetable Crops. Vegetable Yield per acre 1 Nutrient removal, lbs/acre N P 2 O 5 K 2 O Ca Mg Snap beans Total 250 bu 30 20 35 7 3 Broccoli heads 5 tons 20 2 45 other 145 8 165 Total 165 10 210 Cabbage Total 20 tons 125 30 130 28 10 Carrots roots 25 tons 80 20 200 tops 65 5 145 Total 145 25 345 Cauliflower 6 tons 45 18 43 4 3 Celery tops 50 tons 170 380 roots 25 55 Total 195 80 435 110 27 Cucumbers 24 tons 100-200 33-72 100-400 Eggplant 16 tons 207 46 34 Vegetable Program
Step 4: do some math! Cubic yards of compost required to cover a specific area: ft 2 x inches of compost x 0.0031 = yd 3 Example: 43,560 ft 2 x 1 inch of compost x 0.0031 = 135 yd 3 per acre Vegetable Program
Nutrient Content Compost application rate (yd 3 /area) x nutrient content (lbs/yd 3 ) = lbs of nutrient/specific area Example: x (from test) = 135 yd 3 /A 6.56 lbs N/yd 3 885.6 lbs Total N/A Vegetable Program
Calculating Soluble Nitrate in compost Convert moist weight mg/kg to %: 146 mg NO 3 /kg (from test) x 0.0001 = 0.0146 % Calculate lbs NO 3 /yd 3 of compost: 0.0146% NO 3 x bulk density 1,025 1025 lbs/yd 3 (from test) /100 = 0.15 lbs NO 3 /yd 3. Calculate soluble nitrate available to your crop at the time of application: 0.15 lbs NO 3 /yd 3 x 135 yd 3 /acre = 20.25 lbs NO 3 /acre 135 yd 3 /acre Vegetable Program
Calculating Plant Available Nitrogen (PAN) from compost First season: 10% (885.6 lbs Total N/acre x 0.1) = 88.56 lbs PAN Second season: 5% (885.6 lbs Total N/acre x 0.05) = 44.28 lbs PAN Third season: 2.5% (885.6 lbs Total N/acre x 0.025) = 22.14 lbs PAN Vegetable Program
Calculating Phosphorus in compost Convert P to P 2 O 5 : 0.86 lbs P/yd 3 (from test) x 2.29 = 1.97 lbs P 2 O 5 /yd 3 P 2 O 5 in compost: 135 yd/acre x 1.97 lbs P2O5/yd 3 = 266 lbs P 2 O 5 /acre Vegetable Program
Release Rates Quick Very Slow Vegetable Program
Calculating Potassium in compost Convert K to K 2 O: 1.66 lbs K/yd 3 (from test) x 1.2 = 1.99 lbs K 2 O /yd 3 K 2 O in compost: 135 yd/acre x 1.97 1.99 lbs P2O5/yd K 3 2 O 3 = 269 lbs P 2 O 5 /acre Vegetable Program
Common Organic Fertilizers N: dried blood, Chilean nitrate*, seed meals (alfalfa, soy, peanut) P: rock phosphate, bone meal, whey K: potassium sulfate, sul-po-mag, greensand Ca: lime, gypsum Mg: lime, sul-po-mag, epsom salts Blends: pelletized poultry manure, etc. Micros: borax, chelates, sulfates
Blood meal 12-0-0 Quick-release form of organic N Used for side dressing, potting mixes Watch rates, timing, to avoid NH 3 toxicity Avoid direct root contact as it can burn $82 for 50lb = $13.67 per lb N
Chilean nitrate 16-0-0 highly soluble, thus available to plants NaNO 3 mined from a desert in northern Chile cannot exceed 20% of crop s total N need 26% sodium but no big deal in small quantities $45 for 50 lb = $5.62 per lb N
Rock phosphate 0-3-0 Contains ~30% P; only ~1-3% is available, used to build up reservoir of P in soil Colloidal phosphate less total P ~16%, but it is more available ph affects availability of P, so lime first $24 for $50 lb = $16.00 per lb available P @ 3%
Steamed Bone Meal 1-11-0 + 22% Ca rapidly soluble but expensive source of P good for banding and side dressing Precipitated has twice as much available P, little N; powdery thus hard to work with. $42 for 50 lb = $7.64 per lb P
Bone Char 0-16-0 calcined (burned) bone meal 16% available P 2 O 5 and 32% total phosphate significantly less needed than rock phosphate to supply same amount of available P $25 for $50 lb = $2 per lb available P Not likely to be available anymore
Sul-Po-Mag 0-0-22 + 11% Mg mined mineral K and Mg source use only if Mg is needed, otherwise KSO 4 soluble, use in cropping season $38 for 50 lb = $3.45 per lb K
Potassium sulfate 0-0-52 both natural (mined) and synthetic forms, check that brand is allowed before buying inexpensive material that adds K without any other cations Relatively soluble, should be used when crops are growing or can be lost to leaching $54 for 50 lb = $2.16per lb K
Greensand and Granite Dust Granite dust (0-0-6) Greensand (0-1-7 with 3% Mg) Slow release K sources, used to build soil reservoir, not for immediate crop needs
Limestone Dolomite contains about 25% calcium and about 10% magnesium = best value for Mg Calcite contains ~38% calcium Use either one unless Mg is high or low
Seed Meals alfalfa 2-1-2, soy 7-2-1, peanut 8-1-1, etc. medium release rate several months won t burn plants good value per unit of N, animal feed prices
50 lb soy meal $17 = $4.86 per lb N 50 lb peanut meal = $32 = $8 per lb N 50 lb alfalfa meal $31 = $20.67 per lb N
$11/ lb N $14/ lb P $14/ lb K
$9/ lb N $15/ lb P $11/ lb K
Trace Minerals Azomite 2.5% K, 5% Ca, 67 trace elements and minerals Acronym for A to Z of minerals including trace minerals Derived from volcanic mineral deposit Contains over 70 minerals and trace elements Micronized or powder for quick release Granular for slow release Does contain 6.2 ppm of lead, 21.7 ppm of cesium, 4 ppm of uranium (http://www.nantahala-farm.com/azomite-certificate-of-analysis-s.shtml) Greensand 0-1-7, $29.50 for 50# For soils that also need K Contains 30 trace minerals - micronutrients
How To Manage for N Availability Assume ¾ availability for most organic bagged fertilizer (so multiply your fertilizer # by 1.3) Use slow(er) release materials at planting time. Use PSNT 30 days after planting if in doubt about sidedress needs. Sidedress with quicker release materials 30-40 days after planting when needed.