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Nutrient management for organic vegetable production in NC Part I.

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Presentation on theme: "Nutrient management for organic vegetable production in NC Part I."— Presentation transcript:

1 Nutrient management for organic vegetable production in NC Part I

2 Nitrogen Phosphorus Potassium Average rates of N, P 2 O 5 and K 2 O applied to vegetable crops in the US Why are these rates so high ? (lbs/acre)

3 Most growers believe that high rates of nutrients are needed to produce high yields of high quality vegetables

4 Jalapeno pepper production in Fresno County, California Total cost of production: $4392 Total fertilizer costs: $170 Fertilizer costs = 4% of total costs

5 N K Ca Mg P S macronutrients micronutrients air & water Soil ~ 16 elements have been identified as essential for the growth of all plants C O H Cl Fe Mn Zn B Cu Mo Na Co Si VNi Needed by some plants

6 Micronutrients are critical components of enzymes

7 Soil solids contain nutrients minerals organic matter

8 exchangeable ions Soil soup Humus Clay Na + Ca +2 H+H+ K+K+ Mg +2 K+K+ H20H20 H20H20 H20H20 H20H20 H20H20 H20H20 H20H20 H20H20 H20H20 H20H20 H20H20 H20H20 H20H20 H20H20 H20H20 H20H20 H20H20 Soil water contains nutrients

9 What’s in the soil soup ?? Adapted from Brady and Weil (2002) Ca +2 NO 3 - Ca +2 K+K+ K+K+ Mg +2 Ca +2 Mg +2 Ca +2 Mg +2 Ca +2 NO 3 - SO 4 -2 NO 3 - H 2 PO 4 - DOM Cu +3 Fe +3 Zn +2

10 Which forms of nutrients are available to plants ? solution exchangeable “active” OM passive “OM” weatherable minerals

11 Re-seasoning the soup Modified from Havlin et al. (1999) Poorly buffered Highly buffered

12 …… Nutrient availability Crop yield Deficiency Symptoms

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15 Understanding nutrient uptake Transpirational stream Root growth H20H20 H20H20 Root exudates activate soil microbes

16 ? Acute root disease Feed the soil vs. Feed the crop ? Chronic root malfunction Both strategies are important ! Healthy roots need available nutrients ! Unhealthy roots use nutrients inefficiently…

17 The acid infertility complex

18 Nutrient availability varies with pH

19 Understanding aluminum toxicity Toxic forms of Al are bioavailable at low pHs Aluminum toxicity is minimal above pH 5.5

20 Exchangeable Al +3 Brady and Weil (2002) 100% 50% 0% 75% 25% Percentage of maximum cation exchange capacity

21 Avoid over-liming !! Micronutrient deficiencies frequently occur when naturally acid soils are over-limed

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