PRIMARY (MACRO) NUTRIENTS

Transcription

1 Session 8 Earth: Fertility in the forest garden Lewis McNeill May 2014 Recap on nutrients Sixteen plant food nutrients are essential for proper plant and crop development. Each is equally important to the plant, yet each is required in vastly different amounts. These differences have led to the grouping of these essential elements into three categories; macro (primary) nutrients, secondary nutrients, and micronutrients. PRIMARY (MACRO) NUTRIENTS Primary (macro) nutrients are nitrogen, phosphorus, and potassium. They are the most important nutrients to consider when thinking about building fertility into your forest garden as they are needed in the greatest total quantity by plants. NITROGEN N Necessary for formation of amino acids, the building blocks of protein Essential for plant cell division, vital for plant growth Directly involved in photosynthesis Necessary component of vitamins Aids in production and use of carbohydrates Affects energy reactions in the plant PHOSPHORUS P Involved in photosynthesis, respiration, energy storage and transfer, cell Promotes early root formation and growth Improves quality of fruits, vegetables, and grains Vital to seed formation Helps plants survive harsh winter conditions Increases water-use efficiency Hastens maturity division, and enlargement POTASSIUM K Carbohydrate metabolism and the break down and translocation of starches Increases photosynthesis Increases water-use efficiency Essential to protein synthesis Important in fruit formation Activates enzymes and controls their reaction rates Improves quality of seeds and fruit Improves winter hardiness Increases disease resistance SECONDARY NUTRIENTS The secondary nutrients are calcium, magnesium, and sulphur. For most crops, these three are needed in lesser amounts that the primary nutrients. CALCIUM Ca Utilized for Continuous cell division and formation essential for root tip growth Involved in nitrogen metabolism Reduces plant respiration Aids translocation of photosynthesis from leaves to fruiting organs Increases fruit set Determines soil ph Stimulates microbial activity MAGNESIUM Mg Key element of chlorophyll production Improves utilization and mobility of phosphorus Activator and component of many plant enzymes Increases iron utilization in plants Influences earliness and uniformity of maturity 1

2 SULPHUR S Integral part of amino acids Helps develop enzymes and vitamins Promotes nodule formation on legumes Aids in seed production Necessary in chlorophyll formation (though it isn t one of the constituents) MICRONUTRIENTS The micronutrients are boron, chlorine, cooper, iron, manganese, molybdenum, and zinc. These plant food elements are used in very small amounts, but they are just as important to plant development and profitable crop production as the major nutrients. Especially, they work "behind the scene" as activators of many plant functions. BORON B Essential of germination of pollen grains and growth of pollen tubes Essential for seed and cell wall formation Promotes maturity Necessary for sugar translocation Affects nitrogen and carbohydrate CHLORINE Cl Not much information about its functions Interferes with P uptake Enhances maturity of small grains on some soils COPPER Cu Catalyzes several plant processes Major function in photosynthesis Major function in reproductive stages Indirect role in chlorophyll production Increases sugar content Intensifies color Improves flavour of fruits and vegetables IRON Fe Promotes formation of chlorophyll Acts as an oxygen carrier Reactions involving cell division and growth MANGANESE Mn Functions as a part of certain enzyme systems Aids in chlorophyll synthesis Increases the availability of P and Ca MOLYBDENUM Mo Required to reduces nitrates to ammonium in plant Aids in the formation of legume nodules Needed to convert inorganic phosphates to organic forms in the plant ZINC Zn Aids plant growth hormones and enzyme system Necessary for chlorophyll production Necessary for carbohydrate formation Necessary for starch formation Aids in seed formation In addition to the 13 nutrients listed above, plants require Carbon, Hydrogen, and Oxygen, which are extracted from air and water to make up the bulk of plant weight. Soil ph is one of the most important soil properties that affects the availability of nutrients. Macronutrients tend to be less available in soils with low ph. Micronutrients tend to be less available in soils with high ph. An apparent nutrient deficiency in a plant may be down to soil ph being too acid or alkaline. 2

3 Fig.1 Soil triangle Fig. 2 Comparative size of sands, silt and clay. If clay was the size of the dot on the page, silt and sands would be a comparative size. 3

4 Fig. 3 Soil texture by feel chart 4

5 Fig. 4 The soil food web (from The Holistic Orchard) 5

6 Fig. 5 Root nodules on N-fixing plant Fig. 6 N-fixing in an actinorhizal plant (woody plant that forms symbiosis with frankia spp bacteria) 6

7 Fig. 7 Russian comfrey Bocking 14 ; one of the easiest and versatile onsite nutrient sources Fig. 8 Amazing mycorrhizae! This close up shot shows the tiny hyphae connected to a tree s feeder root Fig. 9 Here a Mycorrhizal hyphae has lassoed a root-eating nematode, thereby protecting the host tree! 7

8 The Soil Food Web Gardening Rules (from Teaming with Microbes) 1. Some plants prefer soils dominated by fungi; others prefer soils dominated by bacteria. 2. Vegetables, annuals and grasses prefer their nitrogen in nitrate form and do best in bacterially dominated soils. 3. Perennials, shrubs, and trees prefer their nitrogen in ammonium form and do best in fungal dominated soils. 4. Compost can be used to inoculate beneficial microbes and life into soils around your yard and introduce, maintain or alter the soil food web in a particular area 5. Adding compost to the surface of the soil will inoculate the soil with the same soil food web in the compost. 6. Brown organic materials support fungi while green supports bacteria. 7. Fresh, green mulches tend to support bacterial populations; aged, brown mulches support fungal growth. 8. Mulch laid on the surface tends to support fungi while mulch worked into the soil tends to support bacteria. 9. If you wet and grind mulch thoroughly, it speeds up bacterial colonization. 10. Coarse, dryer mulches support fungal activity. 11. Sugars help the bacteria multiply and grow while kelp, humic and fulvic acids and phosphate rock dusts help fungi grow. 12. Depending on the compost and the nutrients added, you can make teas that are fungal dominated, bacterially dominated or an even ratio of both. 13. Compost teas are very sensitive to chlorine and preservatives in the brewing water and ingredients. 14. Applications of synthetic fertilizers kill off most or all of the soil food web microbes. 15. Stay away from additives that have high NPK numbers. 16. Immediately follow any chemical spraying or soil drenching with an application of compost tea. 17. The roots of conifers as well as hardwood trees including birch, oak, beech, and hickory form mycorrhizae with Ectomycorrhizal fungi. 18. Shrubs and softwood trees form mycorrhizae with Endomycorrhizal fungi. 19. Rototilling and excessive soil turning destroys or severely damages the soil food web. 20. Always mix endomycorrhizal fungi with the seeds of annuals and vegetables at planting time or apply them to roots at transplanting time. Reading list: Creating a forest garden, working with nature to grow edible crops, Chapter 6: Fertility in forest gardens, Martin Crawford Teaming with Microbes, The organic gardener s guide to the soil food web, Jeff Lowenfels & Wayne Lewis Teaming with Nutrients, The organic gardeners guide to optimizing plant nutrition, Jeff Lowenfells Roots Demystified, change your gardening habits to help root thrive, Robert Kourik The Holistic orchard: tree fruits and berries the biological way, Michael Phillips Interesting and accessible paper on carbon sequestration in soils The most exemplary nature is that of the topsoil. It increases by experience, by the passage of seasons over it, growth rising out of it and returning to it, not by ambition or aggressiveness. It is enriched by all things that die and enter in to it. It keeps the past, not as history or as memory, but as richness, new possibility. It s fertility is always building out of death into promise. Death is the bridge or the tunnel by which its past enters its future. - Wendell Berry 8