Diagnosing Plant Nutrient Status Under Different Irrigation Levels in Southwest KS.

The use of visual symptoms has long been used to identify nutrient deficiency. However, often times the application of the proposed deficient nutrient does not result in the correction of the observed visual symptoms. This is because essential nutrients do not operate independently of each other or independently of the overall plant health and growing condition. A study was initiated in 2016 to utilize both soil and plant analysis to identify toxicities or hidden deficiencies that could be limiting corn yield at various irrigation capacities. Soil sample prior to planting and plant sample at tasseling were collected from corn grown under five irrigation capacities and dryland conditions. Irrigation capacities were 0.25, 0.17, 0.13, 0.10, 0.08 inches/day. Relationships among plant nutrients and corn yield was developed to identify possible nutrients that could be limiting corn yield. Soil analysis showed soil pH of around 8 and organic matter of around 2 %. In general, as expected soil pH did increase with reduction in irrigation capacity. Sulphur (S) was the only nutrient found to be of concern within the soil analysis. Sulfur was also found to be of concern in the plant analysis. As S concentration was right at the lower limit of the sufficiency level. All other nutrients were within the required sufficiency level. However, Mn (110 ppm) concentration was found to be higher than that of Fe (94 ppm). Whenever Mn concentration in a plant is higher than that of Fe regardless of concentration, it is an indication of Fe deficiency. Moreover, a significant relationship (P value =0.05) was observed for plant Fe concentration and corn grain yield at the 10% significance level. Likewise, an even stronger significant relationship (P value = 0.035) was observed for Fe/Mn ratio and corn grain yield at the 5% significance level. These results suggest that Fe deficiency could be the hidden deficiency limiting corn yield.