The 2011 growing season was a very busy plant analysis season for AGVISE. In this article, I would like to share some summary data with you. Table 1 is a summary of the plant analysis results for corn, wheat, and soybeans. Only nutrients with a significant percent of the samples testing below the critical level have been included in the table. In the case of wheat and corn, the table is a summary of three different growth stages. The data may be skewed to the low side because some samples in this summary may have been taken to diagnose visual symptoms of nutrient deficiency observed in the field.
The corn data indicates we had a significant number of fields testing low in nitrogen, phosphorus, potassium, sulfur and zinc. The large number of tissue samples testing low in nitrogen may be partially due to the loss of nitrogen from both fall and spring applications. The above normal precipitation events certainly resulted in both leaching and denrificaton of nitrogen in many of the fields.
The wheat tissue data shows many of the same trends noted in corn. A significant number of fields tested low in nitrogen, phosphorus and potassium. Sulfur does not appear to be as much of an issue on wheat as corn. The number of wheat tissue samples testing below the critical level for zinc is somewhat surprising to me. The large number of wheat tissue samples testing below the critical level for zinc could be due to the fact most wheat tissue samples come from areas where zinc fertilizer has never been applied. Chloride is another issue in the wheat tissue samples we tested in 2011. 43% of the wheat tissue samples tested below the critical level of chloride. This number again should not be surprising as many of the wheat fields from our western trade area do not have a history of potash (potassium chloride) application.
The data from soybeans indicates fewer nutrient issues than either wheat or corn. The two nutrients with the highest frequency of samples testing below the critical level are zinc and copper. I have seen very little research on soybean yield responses to either zinc or copper. It is possible that the critical level for these nutrients needs to be updated with new research. I do not know what impact, if any, these levels of zinc or copper will have on yield.
In summary, we need to be aware that a significant percentage of tissue samples tested below the critical levels for macronutrients nitrogen, phosphorus and potassium. Eliminating deficiencies of these macronutrients should be the first priority. There are also some issues with sulfur, chloride, zinc and copper which should be addressed once the problems with N, P and K have been resolved.