If you plan to cover soil with plastic mulch, test it the autumn before spring planting to ascertain its pH and nutrient needs and to learn if it is bullied by little, round worms known as nematodes. Soil to be covered by plastic mulch is typically disked or tilled at least one month before the bend to split it up, remove clods, rocks and debris and to include the residues of earlier crops.
Soil Testing
Most garden supply centres sell fundamental soil-testing kits that will reveal the soil pH and indicate the presence or lack of the significant soil nutrients nitrogen, phosphorus and potassium. Get in touch with your extension service about testing your soil for nematodes. If your soil has nematodes, fumigate the soil before planting with a multi purpose fumigate that controls nematodes, soilborne diseases and weeds.
Adjusting Soil pH
Soil pH, optimally adjusted at the fall before planting, measures the acidity or alkalinity of the soil over a scale of 1 to 14. Soils below 7, usually found in areas with more rainfall, are more acidic. Soils above 7, usually located in arid climates, are more alkaline. Soil pH affects the ability of plants to utilize soil nutrients, and different plants have different requirements. Soil pH is typically lowered with the addition of sulfur and increased with the addition of lime.
Adding Fertilizer
Following the needs indicated by the soil test, add fertilizer before planting and mulching. At least half the nitrogen conditions should be met with a nitrate. Nitrates can leach in the soil, but they are protected by plastic mulch. Organisms in the soil change ammonium forms of nitrogen into nitrates. If you fumigate your soil to destroy nematodes, adding ammonium forms of nitrogen may be toxic to the harvest.
Fertilizer With Drip Irrigation
If you use drip irrigation, which is standard with plastic mulching, add one half of the nitrogen, phosphorous and potassium before planting and mulching Utilize drip chemicals to bring the remaining balance of nutrients in water-soluble calcium nitrate, sodium nitrate, 15-0-14 or 20-20-20 fertilizer or potassium nitrate. If you include all the fertilizer from the bed before planting and mulching, the crops don’t get as much helpful nutrients. The fertilizer numbers suggest the ratio by weight of nitrogen, phosphorous and potassium.