Does Timing Matter When Sampling Corn and Soybean Tissue for Nutrient Analysis

Tissue analysis can play an important role in determining if corn and soybean are getting adequate nutrition. Tissue samples can be pulled at various stages of development, but one of the most common times is when crops enter the reproductive stages (R1). Prior to R1, corn and soybean are in a rapid growth phase with very high nutrient uptake over several weeks. Sampling at R1 allows us to determine if their nutrient needs are being met, or if a particular nutrient is deficient. But how important is it that the tissue sampling happen right at flowering? If the sampling is a little earlier or later, will you get different results?

We addressed these questions by sampling 6 corn and 6 soybean fields across Ohio (Darke, Highland, Mercer, Miami, Paulding, Ross and Wayne County). At each field, leaves were sampled 2 weeks before, 1 week before, at flowering (R1), 1 week after, 2 weeks after flowering. Tissue samples were dried and analyzed for total nutrient concentrations. The Tri-State Fertilizer Recommendations has sufficiency ranges that indicate if tested samples are ‘below, ‘sufficient’, or ‘above’ normal levels.

The two figures below show macronutrient concentrations with trendlines over the 5-week period for corn and soybean. Over all the sites, macronutrient concentrations varied widely, representing differences in fields, hybrids or varieties and environments. Some nutrient concentrations increased or decreased, while others remained consistent over time. These results demonstrate that nutrient concentrations do fluctuate before and after R1. Therefore, care should be taken to sample as close to flowering as possible, so that the lab results obtained are consistent and meaningful with published reference values (Table below).

Nutrient sufficiency ranges at flowering

(Adapted from Table 24 of Tri-State Fertilizer Recommendations)