Scientific Gardening & Agriculture Guides
From Soil Science to Harvest: Data-Driven Growing
These guides combine horticultural research with practical tools to help you:
- Apply plant physiology principles to spacing decisions
- Calculate nutrient mineralization rates in organic amendments
- Balance soil ecosystems using NPK ratios
For educators: Includes student exercises with solutions. For professionals: Covers commercial-scale calculations.
1. The Science of Plant Spacing
Why Spacing Matters: Light & Root Competition
Plants follow the "Law of the Minimum" - growth is limited by whichever resource (light, water, nutrients) is scarcest. Our spacing tool accounts for:
- Light interception: Leaf Area Index (LAI) requirements for photosynthesis
- Root architecture: Fibrous vs. taproot systems' spatial needs
- Allelopathy: Chemical inhibitors from certain plant roots
Spacing Calculator
Based on peer-reviewed density formulas from:
- Horticultural Science journals
- USDA planting guidelines
- Permaculture design principles
Formula: √(10,000 ÷ plants/ha) = cm spacing
Case Study: Biointensive Spacing
At UC Davis' Student Farm, hexagonal spacing increased yields by 18% compared to rows:
(24" hex)
(12" interplant)
(6" filler)
Calculator input: 19 plants/sq m (vs 12 in rows)
Student Exercise: Spacing Efficiency
Calculate how many more zucchini plants (36" spacing) fit in a 100 sq m area when using offset rows vs. traditional rows:
Traditional: 100 ÷ (3×3) = 11 plants
Offset: 100 ÷ (3×2.6) = 13 plants (18% increase)
The Ecology of Companion Planting
Nitrogen fixation: Beans add 30-50 lbs N/acre to soil through rhizobium symbiosis.
Trap cropping: Radishes attract flea beetles away from brassicas (20% pest reduction).
2. Organic Fertilizer Mineralization
From Amendment to Availability
Organic fertilizers require microbial decomposition before nutrients become plant-available. Our calculator factors:
- C:N ratios: Below 20:1 causes rapid mineralization
- Temperature effects: 10°C drop halves microbial activity
- Lignin content: Woody materials break down slower
Fertilizer Calculator
Converts between units while accounting for:
- First-year availability: 50% N from manure, 10% from bark
- Salt index: Chicken manure (3.0) vs. compost (0.5)
- pH effects: Phosphorus locks up below pH 6.0
N-mineralization = (Total N × % availability) ÷ C:N ratio
Commercial Vegetable Farm Example
To meet 150 lbs N/acre requirement using 4-3-2 compost:
- Calculator determines 3,750 lbs compost/acre (40% first-year N release)
- Adjusts for 6.5 pH (10% P availability)
- Recommends supplemental potassium for fruiting crops
Data source: UW Extension Organic Fertilizer Guidelines
Soil Science Lab Exercise
Calculate how much 5-3-4 fish meal is needed to provide 25 ppm nitrogen to 100 sq ft of raised beds:
25 ppm = 0.5 lbs N/100 sq ft
0.5 ÷ (0.05 × 0.6) = 1.67 lbs fish meal
Organic Material Mineralization Rates
| Material | C:N Ratio | Year 1 N Release | Best Application Timing |
|---|---|---|---|
| Blood meal | 3:1 | 90% | Pre-planting |
| Composted manure | 15:1 | 50% | Fall or spring |
| Wood chips | 400:1 | 5% | Mulch only |
Integrated Soil Fertility Management
For Students: Research Concepts
- Liebig's Barrel: Visualizing limiting factors
- Nutrient cycling: Microbial biomass calculations
- Soil food web: Trophic level interactions
For Professionals: Field Protocols
- Pre-sidedress nitrate tests (PSNT) timing
- Cover crop nitrogen credits calculation
- Bulk density adjustments for compost