Getting Ready for New Garden Seasons at LBCGA

At the beginning of each growing season it is important to add some fertilizer, especially nitrogen, to help your plants grow. Gypsum helps break up the soil and allows for better drainage of salts. Organic compost helps improve soil tilth and adds nutrients such as phosphate and potassium. Soil test results from Wallace Labs show that the garden soil is fertile and has abundant nutrients. Only nitrogen, gypsum and compost are usually needed. A good rule to follow is to only add what you know you need. It is easier to add than to remove things from your soil. If in doubt, get your soil tested.

Some Examples

  • For a full-size plot combine:

    • 12 lbs. Blood meal, feather meal or other organic nitrogen fertilizer with NPK around 15-0-0.

    • 100 lbs. organic compost or manure, enough for about 1.5 inches.

    • 25 lbs. gypsum

    Till or dig into soil. Water deeply. Wait a few days before planting. Wait at least 1 week to plant seeds.

    For your safety, wear a mask when working with fertilizers.

    If you have raised beds or multiple walkways in your plot, reduce by a quarter. You can reduce nitrogen by 2 lbs. if using manure.

  • For a full-size plot combine:

    • 8 lbs. calcium nitrate or ammonium sulfate[1].

    • 100 lbs. compost or manure[2], enough for about 1.5 inches.

    • 25 lbs. gypsum

    Till or dig into soil. Water deeply. Wait a few days before planting. Wait at least 1 week to plant seeds.

    For your safety, wear a mask when working with fertilizers.

    If you have raised beds or multiple walkways in your plot, reduce by a quarter.

    Ammonium sulfate will lower soil pH.

    You can reduce nitrogen by 2 lbs. if using manure.

  • For a full-size plot combine:

    • 150 lbs. horse manure, enough for about 2 inches.

    • 40 lbs. gypsum

    Till or dig into soil. Water deeply. Wait a few days before planting. Wait at least 1 week to plant seeds.

    Consider adding additional nitrogen such as fish emulsion if growth is slow.

Soil Issues

  • High levels of salt in the soil may cause poor seed germination, slower growth and lower production of vegetables.  Manure and nitrogen fertilizers are the main contributors of salt.  Be sure to add gypsum to the soil which will help leach the salts out of the soil.

    To reduce the level of salt, it is suggested to apply the manure as a mulch around plants once they are large enough.  This helps to retain moister in the soil and allows the salts to leach out slowly when they are less likely to affect plant growth.  It can then be mixed into the soil at the end of the growing season.

    Salt levels in soil can be measured with an EC (electrical conductivity) meter.   Budget meters cost around $60 while higher quality models cost hundreds of dollars.  An EC value under 1 is considered normal.  A value between 1 and 2 will affect a few plants.  Values over 4 will cause moderate damage to many plants.

    The chart here shows the sensitivity to salt of some common vegetables.  For example, beans will be affected if the EC value is over 1.0.  Broccoli and tomatoes are more salt tolerant.

    Source: 
    University of California IPM
    http://ipm.ucanr.edu/PMG/GARDEN/ENVIRON/salttoxicity.html

    Salt index information:  
    https://www.canr.msu.edu/news/avoiding_salt_injury_from_nitrogen_fertilizers_in_orchards

  • Zinc is an important nutrient.  The optimal concentration of zinc is several parts per million for best growth.  Our native soil has about 3 times that amount. If zinc is too high, growth is inhibited by toxicity. Sensitive plants such as woody plants need plant available zinc below about 30 parts per million. Herbaceous plants need zinc below about 50 parts per million. Excessive zinc causes stunting, dieback and discoloration. High zinc restricts the uptake of potassium and other micronutrients.

    Avoid using fertilizers containing zinc such as Miracle Gro, Azomite, Ironite, and enhanced bagged compost products like Bumper Crop.

  • Aluminum restricts growth by interfering with the metabolism of phosphorus and calcium.  It causes stunting and discoloration.  Foliage may turn a dull gray green.  Aluminum is high in poorly aerated soil and in overly acidic soils.

    Make sure your soil doesn’t get compacted by poor watering or lack of compost.  Do not allow your soil to become acidic by applying too much sulfur.  Soluble calcium helps to reduce the toxicity of aluminum.

  • The pH (hydrogen ion concentration) value of your soil is important to know.  If the value is too low or too high, your plants may have problems absorbing nutrients from the soil.  A value of 7 is neutral.  Below 7 is acidic and above 7 is alkaline.  A desirable range is between 6.5 and 7.5.  Optimal for most garden plants is between 6.5 and 7.0.

    Adding sulfur to your soil will lower your pH.  Fertilizers like ammonium sulfate have a high concentration of sulfur.  Lime can be used to raise the pH level.

    Easy to use pH soil testing kits are found at most garden shops and online.  It is a good idea to check your soil about once a year.

  • In 2021, soil tests were performed on garden plots and under trees in the orchard. The results have been published here.

Detailed Information

  • Fertilizers usually have 3 numbers on the label that tell you how much nitrogen (N), phosphate (P) and potassium (K) they contain by weight.  For example, a fertilizer with an NPK of 10-15-5 means that 10% is nitrogen, 15% is phosphate and 5% is potassium.  The rest (70%) are other ingredients.

    Common high nitrogen fertilizers are:

    • Ammonium sulfate (21-0-0). Contains 28% sulfur. pH lowering

    • Calcium nitrate (15-0-0). Contains 17% calcium. pH neutral

    • Urea (47-0-0). pH neutral.

    • Blood meal (12-1-1). pH lowering. May burn young plants if too much.

    • Feather meal (12-0-0). pH neutral.

    • Fish emulsion (5-1-1). pH neutral.

    Blended fertilizer products usually add nitrogen from one of these or other sources so check the label.  It is more economical to buy a nitrogen fertilizer without additional ingredients that you probably don’t need.

    For an average plot size of 600 sq. ft., this chart will help you calculate the amount you may need.  Adding too much nitrogen may harm plants.

    10-0-0 (16 lbs)
    15-0-0 (12lbs)
    21-0-0 (8lb)
    27-0-0 (6lb)
    48-0-0 (4lb)

    Small amounts of nitrogen may be added every 3 to 4 weeks during the growing season.  If compost is not added to the soil, it may be necessary to add a small amount of phosphate at the rate of 4 lbs. of a 0-20-0 fertilizer once a year.  Scale down these values if your growing area is smaller.

  • For a typical plot size of 600 sq. ft., about 25 lbs. of gypsum per growing season is sufficient.  Double this amount if you have high levels of salt in your soil.  Gypsum needs to be mixed well into the soil to avoid clumping when wet.  Granular form is usually easier to apply but is costlier.  Gypsum (calcium sulfate) contains sulfur and breathing the dust may injure lungs.  It is strongly recommended to wear a mask and gloves when applying.

  • For a typical plot size of 600 sq. ft., about 100 lbs. of compost is sufficient.  This usually works out to be around 1.5” deep.  It is best to mix it in to the depth of the root zone which will help roots grow deep and strong.

    You can purchase compost at most garden stores or use the horse manure compost provided by the garden.  Composted manure (horse, cow, chicken) will give you nitrogen but contains high levels of salt. See issues with salt below.

    If you compost your garden waste, be sure that it maintains a temperature of 150 degrees for 5 days before using otherwise you may be spreading harmful pathogens into your soil.

    Mulch (wood chips) and the spent brewer grain (spelt) provided in the SE corner are not composted and should not be mixed into the soil.