Broadcast amendments

Broadcast amendments are applied prior to planting to adjust soil pH or to increase the supply of Ca, K, N and P. Rock-phosphate, lime, animal manure and well-composted organic material have all been used successfully in pineapple culture systems under the right conditions. Benefits from broadcast amendments should not be assumed; thus, diagnostic soil testing is needed to verify specific deficits, such as soil pH (for lime), Ca and K (for lime and manures) and P (for phosphates).

Amendments must be broadcast uniformly and incorporated to the desired depth to provide the most benefit for the developing root system. Major problems can arise when soil amendments are not applied and incorporated uniformly. Among the serious problems is a localized high pH, which favours the infection of susceptible pineapple plants by Phytophthora and Pythium fungi (see Rohrbach and Johnson, Chapter 9, this volume). When manure is used, extreme care must be taken to avoid adverse effects in areas where the manure is temporarily stored in the field before spreading, or where spreading is not uniform and the quantities applied exceed desirable levels. Salts leached from cattle manure can severely restrict growth. Similarly, high soil pH resulting from the application of chicken manure or coral scraped from feedlot sites has led to spotty outbreaks of heart rot caused by Phytophthora.

Pineapple responds well to the use of organic manures. Growers in 18th-century England allowed sheep to trample their droppings and urine into oak leaves that would be used to make potting compost. More recently, experiments in Hawaii with sewage sludge, chicken manure and dairy or feedlot cattle manure all resulted in substantial yield increases from incorporation of up to about 45 t ha-1 (about 20 tons acre-1) of manure into lands that had been continuously planted to pineapple for ten to 15 crop cycles. Manures are especially regarded for their high K content. However, virtually all broadcast amendments need to be tested and monitored to ensure that adequate nutrient concentrations are present. To ensure that no surprises occur from the use of manures, representative samples should be analysed both to identify nutrient levels of key elements and to determine pH and soluble salt levels.

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