Canola Response to Nitrogen, Sulfur, Phosphorus, and Potassium Fertilization in Arkansas

Canola (Brassica rapa) is an oilseed crop that is related to broccoli (Brassica oleracea var Italica) and turnip (Brassica campestris var Rapifera). The name ‘canola’ actually stands for ‘Canadian oil, low acid’. Canola’s low erucic acid content differentiates it from rapeseed (Brassica napus) and is sometimes referred to as LEAR or ‘low erucic acid rapeseed.’ Canola seed contains about 40% oil and increasing its production in the southern U.S. is of interest for biofuel production. Canola is grown on just over 1.1 million acres in the U.S. with about 90% of the acreage in North Dakota where it is planted in the spring (USDA-NASS, 2008). The average canola yield in the U.S. usually ranges from about 1200 to 1600 lb/acre (24 to 32 bu/acre). In the southern USA, canola is planted in the fall and harvested in the late spring similar to winter wheat (Triticum aestivum). For canola to be successfully grown and adopted by growers, agronomic recommendations regarding appropriate fertilizer rates must be developed. Fertilizer recommendations from the University of Kentucky suggest canola should receive about 120 lb N/acre (Herbeck and Murdock, 1992), performs best when soil pH is between 6.0 and 7.0, is sensitive to P deficiency, and seldom responds to S despite its high S requirement. Our overall research goal is to develop research-based fertilizer recommendations for canola varieties adapted to Arkansas. Our research objectives were to determine canola yield responses to i) P and K fertilizer rates, ii) S fertilization, and iii) N fertilizer rate, source, and application time in eastern Arkansas.