Temporal Variability in Tissue Nutrient Concentration.

The use of plant tissue test analysis for mineral concentrations as an alternative method for fertilizer recommendation has steadily gained interest by farmers and crop advisers in Oklahoma. A study was conducted at Lake Carl Blackwell near Stillwater, OK to evaluate the stability of corn nutrient concentrations across time of day, among days and growth stages as affected by fertilizer application as a tool for mid-season recommendation. Leaf tissue samples from fertilized and unfertilized fields were collected at V4, V8 and R1/R2 growth stages in the morning, noon and evening for three consecutive days (day 1, day 2, and day 3). Samples were analyzed for macronutrients (N, P, K, Ca, Mg, Mn) and micronutrients (S, Cu, Bo, Fe, and Zn) concentrations. Tissue concentrations of all nutrients varied widely among time-of-the-day and among days at all stages for both fertilized and unfertilized plots. Nutrient concentrations generally were highest in the morning and lowest in the evening regardless of sampling day, stage of crop or fertilization. More variability in nutrient concentrations were observed among days at V8 than at V4 and R1/R2 corn. However, fertilizer application and time-of-the-day caused more nutrient content fluctuations at V4 and R1/R2 stages. While the use of plant analysis remains a useful tool in observing crop status, it should be noted that nutrient concentrations varies depending on the time of the day, sampling day, growth stages and fertilization. Thus, plant tissue analysis should not be used to provide mid-season nutrient recommendation.