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Fluid Journal : Fall 2012
Fall 2012 The Fluid Journal 14 Study includes major vegetable and fruit crops grown on calcareous soils in Texas. Establishing Realistic Nutrient Removal Values For Major Crops The Fluid Journal • Ofﬁcial Journal of the Fluid Fertilizer Foundation • Fall 2012 • Vol. 20, No. 4, Issue# 78 The impacts of fertilizer use on crop productivity and basic nutritional quality parameters (proteins, minerals, vitamins, and essential oils) are well documented. Relatively high levels of fertilizer applications are required to ensure adequate yields and quality of many high-value crops. During the course of the growing season, crops take up and accumulate various nutrients in biomass, some of which are eventually removed from the site with harvested products. Nutrients in crop residues that are left in the field can partially add to soil nutrient reserves as the residues decompose. Information regarding crop nutrient removal amounts is essential in determining the amounts that must be reapplied to sustain yields and quality while maintaining soil fertility. Nutrient uptake is influenced by soil, climate, and plant factors. Low soil moisture, poor aeration due to compaction or excessive moisture, low soil temperatures, unfavorable pH conditions in the root zone, nutrient imbalances, and other factors may restrict uptake of plant nutrients. Plant factors such as rooting density and growth rate as well as soil nutrient imbalances can also limit nutrient uptake rates and eventually result in poor crop yields and quality even though soils contain adequate nutrient levels. This is often the case in the predominantly calcareous soils in South Texas and other major production regions where excessive levels of soil calcium (Ca) and magnesium (Mg) can interfere with the availability and uptake of potassium (K), leading to an apparent K deficiency. Information regarding nutrient removal amounts is essential in establishing accurate crop requirements (amounts) as well as the appropriate placement, application methods, and times. Summary: Selected for this study were major fruit and vegetable crops grown on calcareous soils in South Texas. Nutrient removal amounts were estimated for spring-grown muskmelons (2011) and onions planted in the fall (October) and harvested in the spring (April, 2009). Removal rates by grapefruits from commercial orchards were also estimated. Preplant soil N, P2O5 and K2O test levels were slightly lower in 2011 than in previous years. Melon yields ranged from 11 to 19 t.A-1 and were generally greater than those recorded in 2009. Estimated nutrient removal amounts in 2011 ranged from Nat45to84lbs/A,Pat7to17 lbs/A and K at 60 to 128 lbs/A compared to N at 18 to 37 lbs/A, Pat7to11lbs/AandKat44to 90 lbs/A in 2009. Nutrient removal estimates for sweet onion were also higher in 2011 than in 2009, consistent with higher yields in 2011. Grapefruit yields averaged 311 eighty-pound boxes per acre (12.4 tons/A of fresh fruit) and nutrient removal estimates ranged from 24 to 31 lbs/A of N,6to9lbs/AofP,and60to71 lbs/A of K. Dr. John Jifon
Late Spring 2012