Nutrient Management Research Database

• Tissue analysis can have merit for organic production
• Conventional P and K sufficiency standards should apply to organics, but some modification necessary for N status
• Developing your own database across years most useful

This presentation includes the following sections:

1. Differences in soil test interpretation for organic as compared to conventional
2. How does organic management change soil fertility
3. The theory of nutrient balance
4. What can you infer from a soil test about soil nitrogen status?
5. Tissue analysis in organic production
6. Petiole and whole leaf sampling

1. Differences in soil test interpretation for organic as compared to conventional

Same interpretation for pH, extractable P, extractable K, cation saturation, and micronutrients. However organic matter and N status require adjustments for organic systems.

2. How does organic management change soil fertility

Organically managed soils often have higher Olsen-P and exchangeable K levels.

3. Nutrient Balance

Crops can actually handle a wide range of nutrient ratios, and the economics of attempting to achieve nutrient balance often make it unrealistic.

4. Inferring from soil tests

Soil organic matter is related to total soil N and N mineralization potential. Nitrate-N values need to be interpreted in light of when during the season the samples were taken.

5. Tissue analysis

Nutrient sufficiency/deficiency can usually be predicted with soil test results, so tissue testing is secondary. Organic crops take up the same forms of N and process it identically to conventionally grown crops.

6. Petiole and whole leaf sampling

Tentative petiole nitrate-N levels of 5,000 ppm at early flowering and 2,000 at full bloom are useful for determining sufficiency. Whole leaf sampling is useful for organic production, with a level of 4% at first flower and 3.5% at full bloom indicative of sufficiency/deficiency.