Chicken manure is a rich source of plant nutrients. When properly composted and carefully applied it is a safe soil amendment even for use on organically produced raspberries. Research at Washington State University also suggests that chicken manure and other organic soil amendments can be effective treatments for raspberry root rot. Even so, it's important to monitor soil and plant health for signs of nutrient deficiencies.
Well-drained sandy loam soil rich in plant nutrients and high in organic matter is ideal for raspberries. Red raspberries are vulnerable to root rot, a fungal disease fostered by excess soil moisture or poorly drainage. Applying a balanced fertiliser such as 10-10-10 once or twice a year at the rate of one pound of nitrogen per 100 feet of row is the standard recommendation for raspberry fertiliser. But start any fertilisation program based on a comprehensive soil test. Soils already well supplied with phosphorous and potassium may need only supplemental nitrogen.
Of manure fertilisers, chicken or poultry manure is particularly high in nitrogen. In fact, nitrogen levels in fresh chicken manure can be so high that application can damage tender roots and plant vegetation. But with any organic nutrient source--where plant nutrients are bound up in organic compounds--it's impossible to know exactly how much of any nutrient is available, and precisely when it will be available to plants. There are strict safety regulations regarding manure applications for organic growers. However, properly composted poultry manure can safely be applied any time.
Red raspberries are vulnerable to Phytophthora or raspberry root rot, though the fungal soil disease does little damage to black and purple raspberries. Growing resistant raspberry varieties can help. Rich soils high in organic matter, calcium and nitrogen help suppress the fungus. Planting in poorly drained or clay soils then adding mulch can encourage it. Cornell researchers say amending soil with gypsum and calcium sulphate reduces raspberry root rot.
A 2004 report entitled the Organic Management of Raspberry Root Rot summarises Washington State University's recent research. Applying poultry manure to plants infected with raspberry root rot increased raspberry production by 38 to 71 per cent compared to untreated plants. Only treatment with BioVita, a biologically active soil amendment, was more effective. The study concluded that organic and biological treatments could both improve crop yields and decrease raspberry root rot.
But monitor soil dynamics carefully if you plan to rely on chicken or other poultry manures to fertilise or treat raspberry plants. According to the National Sustainable Agriculture Information Service, chicken and other poultry litters are fairly high in phosphate, and high levels of phosphorus in soils can cause zinc deficiency in raspberries and other brambles. Growing green manures as winter between-row cover crops is one way to add just nitrogen to the soil. Applying cottonseed meal is another high-nitrogen, low-phosphate fertiliser option.