All Foliage No Fruit - Knowledgebase Question

SAVANNAH, Ge
Question by DRWAYNEHODGE
June 30, 2010
Most plants good at making exuberant foliage, but now flowers and fruit, or minimal and drop off. What does the soil need?


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Answer from NGA
June 30, 2010

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Here?s some basic info on fertilizer and nutrients that plants require. The 3 numbers on a fertilizer bag refer to the percentage of N (nitrogen), P (phosphorus), and K (potassium) in the bag. There are different formulations for different purposes. In general terms, nitrogen produces lush green growth, phosphorus helps strengthen stems and produce flowers, and potassium keeps the root system healthy. If you're applying fertilizer to fruiting (e.g., tomatoes) or flowering plants, you're not as interested in the plant developing leaves as you are in it flowers and fruit, so you'd use a formulation lower in nitrogen and higher in phosphorus, such as 15-30-15.

To improve your soil, incorporate plenty of compost. In sandy soils, compost improves soil fertility, water and nutrient retention. In clay soils, it improves fertility and drainage. Add a 4-6 inch layer of compost and incorporate it about 12-18 inches deep. You can use manure if it is well-aged (6 months) or you won't be planting until it has lost it's heat and decomposed. Each planting season, add more compost. Incorporate a balanced fertilizer (e.g., 10-10-10) or add organic fertilizers. Follow package instructions.

Organic sources of nutrients:

Nitrogen: alfalfa meal, blood meal, coffee grounds, cottonseed meal, fish emulsion, seabird guano.
Phosphorus: bone meal, rock phosphate
Potassium: greensand, seaweed, kelp

There are positives and negatives to both organic and chemical fertilizers. Organic fertilizers are made from the remains of once living things, therefore they contain carbon. Inorganic fertilizers are man-made from mineral salts, and contain no carbon. (The definition of organic varies widely, but it usually contains carbon.) Miracle Gro is considered inorganic. At the smallest level that plant roots are taking up nutrients, there is no difference to the plant. However, organic fertilizers (such as fish emulsion, alfalfa meal, blood meal, bone meal) provide long-term benefits to the soil, by giving soil microorganisms and earthworms food. Organic matter also improves the structure and workability of soil over time. Organic fertilizers are less likely to burn plants because they have low concentrations of nutrients (e.g., 5-3-1). Organics are slower working, but remain available to the plants longer. They are usually more expensive.

Inorganic fertilizers are usually less expensive, work faster, and have higher nutrient concentrations (e.g., 15-30-15). However, they leach through the soil faster, and can burn plant roots if improperly applied. Because they contain no organic matter, they don't improve the soil over time. Because they are made of mineral salts, they can cause salt build-up over time.

After planting, add a 1-2 inch layer of mulch. Mulch is great to help retain soil moisture, reduce weeds, and as it breaks down it provides nutrients to the soil. Any organic matter can be used as mulch. Try compost, bark, wood chips, straw, or pine needles. As it breaks down, dig it into your soil and add more.

Other nutrients that plants need, but in lesser amounts, are referred to as micronutrients and include: calcium, magnesium, sulfur, boron, chlorine, copper, iron, molybdenum, and zinc. These are usually available in the soil in sufficient amounts. However, you might wish to have a soil test done to see precisely what is missing.

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