Sign up for email alerts of new Fluid Journal issues!
Fluid Journal : Fluid Journal 2002-2004
Fall 2004 Optimal Nutrient Levels Required For High-yielding Potatoes Drs. Jeff Stark and Bryan Hopkins Summary: Potatoes require optimal levels of essential nutrients throughout the growing season to ensure rapid, steady tuber growth and normal tuber development. Seasonal nutrient requirements vary widely, with crops yielding from 400 to 500 ctw/A taking up nitrogen (N) at the rate of 180 to 240 lbs/A, phosphorus (P) at 25 to 35 lbs/A, potassium (K) at 260 to 320 lbs/ A, and S at 18 to 24 lbs/A during the growing season. Daily nutrient uptake rates during tuber growth also vary greatly, ranging from 2.5 to 4 lbs/A/ day for N, 0.30 to 0.40 lb/A/day for P, 4.0 to 6.0 lbs/A/day for K and 0.10 to 0.15 lbs/A/day for S. Potatoes have a relatively shallow root system and are commonly grown in very intensively managed cropping systems on coarse- textured soils. Consequently, it is important for crop managers to develop an efficient nutrient management program, using the most effective nutrient sources, application timings, and methods of placement. Achieving optimal goals requires an efficient nutrient management program, using the most effective nutrient sources, application timings,and methods of placement. Fluid Journal 1 Crop managers should adopt potato fertilizer practices consistent with the characteristics of the cropping system that efficiently use available equipment, fertilizer materials, and other resources to provide flexibility in responding to changing nutrient requirements. Fertilizer application methods commonly used for potatoes include 1) preplant broadcasting followed by incorporation, 2) banding at markout or planting, 3) sidedressing after planting, 4) applying foliar nutrient sprays, and 5) injecting liquid fertilizer through the sprinkler system. Nitrogen management Efficient N management is an essential part of any potato fertilization program. About 60 percent of the seasonal N requirement is taken up in the first 75 days after planting. Consequently, adequate N must be available to the crop early in the season to allow for sufficient canopy development. Research shows that about 150 to 180 lbs/A from soil and fertilizer N is required to affect the canopy closure needed to provide for optimum plant development and yield. Total seasonal N fertilizer recommendations are presented in Table 1. The recommended rates are based on the total N requirement adjusted for yield potential, soil test NO3-N, and NH4-N in the top 12 inches, plus the previous crop. The recommendations assume an average N rate of 60 lbs/A of mineralized N that is accounted for in the table. Split N. The most efficient N management systems for potatoes use split N management with onehalf to three-fourths of the total seasonal N topdressed and/or applied through the irrigation system in several small applications during tuber growth. Several liquid N sources such as urea ammonium nitrate (28 to 32% N) and ammonium polyphosphate (10-34-0) can be applied by this method. N is also a component of many other liquid fertilizers containing P, K, and S that can be injected through sprinklers. When properly used, split N can significantly increase N-use efficiency and reduce N leaching potential, while improving potato yield and quality. Monitoring N status. Relationships between tuber bulking rates and daily or weekly N requirements can be used to initially estimate in-season N applications. However, weekly petiole NO3-N concentrations should be used to monitor actual plant N status. Petiole NO3-N should be maintained above 15,000 ppm during tuber growth for optimal yield. NO3-N concentrations in the top 18 inches of soil also can be used to monitor N availability. Phosphorus management P recommendations for potatoes are presented in Table 2. The primary factors used in determining potato P recommendations are the soil test P concentration (STPC) and the amount of free or excess soil lime. The rates presented in the table represent the amounts of P2O5 that should be broadcast in the fall or spring to raise the STPC to adequate levels. In addition to the broadcast P recommendation, an additional 40 to 80 lbs/A should be applied in a starter or markout band to improve early P availability. When high rates of P are applied, it is important to make sure that zinc availability is
Fluid Journal 1999-2001
Fluid Journal 2005-2007