Well-rotted or properly composted cattle manure is usually a versatile organic soil improver before growing tomatoes. Well-rotted horse manure can also work, while poultry manure is much more concentrated and requires particular care. No manure should be applied simply because tomatoes are planted every year: the soil may already contain plenty of nutrients.
Cattle, horse or poultry manure: how do they differ?
Mature cattle manure adds organic material and helps improve soil structure, moisture retention and biological activity. Its exact nutrient content varies with the animal’s feed, bedding and storage. It is not a fixed recipe, so use a suitable product and adjust the amount to the soil’s condition.
Horse manure can be useful when fully rotted. If it contains a lot of wood shavings or other fresh carbon-rich bedding, decomposition may temporarily tie up some available nitrogen. Do not put actively heating, fresh material in contact with tender tomato roots.
Poultry manure contains much higher concentrations of nutrients and salts than typical cattle manure. Apply only according to the particular product’s analysis and label. A handful of dried pellets is not equivalent to the same weight of traditional manure.
Should you choose pellets or traditional manure?
Pelleted products vary widely: they may be derived from cattle, poultry, horses or a mixture. Compare nitrogen, phosphorus and potassium on the label and follow the stated rate. Some concentrated products are best incorporated before planting rather than placed in a hole beside roots.
When should you add manure before tomatoes?
Suitable, mature organic material can be worked into garden soil during preparation or spread as a surface amendment, depending on the gardening method. Less decomposed manure needs a longer interval and appropriate safe handling. On edible crops, untreated fresh manure also raises microbiological food-safety concerns.
Avoid putting fresh manure directly into the planting hole. High concentrations of ammonia or soluble salts can damage new roots. If the bed is already rich from previous years, use a soil test or observe the crop before adding more.
Does every tomato plant need manure every year?
No. Organic matter improves soil over time, and nutrients can remain from earlier applications. Adding full amounts repeatedly can build up phosphorus, salts or nitrogen beyond what tomatoes need. Too much nitrogen favours large leaves and soft growth rather than balanced fruiting.
Extra care in a greenhouse or polytunnel
Soil under cover is not washed through by rainfall as often as an outdoor bed. Repeated heavy dressings may gradually increase soluble salts. Check soil condition, watering and nutrient supply before deciding that another large manure application is required. Tomatoes in containers may need a different feeding programme.
Manure from an unknown source can damage tomatoes
Certain persistent herbicides used on grassland, including aminopyralid and clopyralid, can survive through animal feed into manure. Susceptible crops such as tomatoes may develop distorted new shoots and leaves. Ask the supplier about the origin of the manure; where there is doubt, test a small sample with sensitive plants before spreading it across the whole vegetable plot.
Not every twisted tomato leaf is caused by herbicide. Heat, moisture stress and pests can create similar concerns. Our guide to why tomato leaves curl helps narrow the diagnosis.
Is manure enough for the entire tomato season?
Not always. Tomatoes need a balanced supply of nutrients throughout growth and fruiting. A rich manure dressing may supply ample nitrogen but cannot guarantee the right balance of potassium and other elements later. Use soil analysis and product directions, and avoid adding more high-nitrogen material merely because fruits are developing.
Sources
RHS – Weedkiller contamination in manure; University of Minnesota Extension – Growing tomatoes.