The first funding period began on October 1 2013, but we advanced essential work since the spring of that year with complementary funding from other sources to start sooner and be able to include the 2013 crop year in the project and also work with crops to be planted in 2014. We could do this by delaying chemical analyses and study of all tissue samples until the beginning of the funding period. Therefore, at this time we have completed preliminary results for 2013 crop year, and are harvesting the crops for the 2nd crop year (2014). In 2013, tissue samples and grain yields were collected from plots of field response trials established at several ISU research farms. There were 33 soybean trials (16 for P and 17 for K; and 18 with tillage and 15 with no-till) and 30 corn trials (11 for P and 19 for K; and 20 with tillage and 10 with no-till). In 2013 we sampled plants at the V6 growth stage in June, sampled corn leaves at the R1 stage and soybean leaves at the R2-R3 stage, harvested grain yield, and took soil samples for the 2014 trials. Since January 2014 we worked on data management and new field trials.
Data management: We worked on corn and soybean data collected in 2013 to study relationships between tissue-test concentrations and grain yield response. Results summarized in the report figures for this first year suggest that tissue testing has potential to be used as a diagnostic tool only for P in corn, but not for others. Even in this case, however, tissue testing seems no better than soil testing as has been demonstrated by previous research. However, no strong conclusions or estimates of tissue sufficiency levels are possible until data from trials established in 2014 are available. We need observations from another year and should consider year effects since rainfall amount and distribution affect the yield response to fertilization.
Work for new field trials: In spring we established 63 trials (29 with soybean and 34 with corn), and collected tissue samples as for the previous year (plants at V6 and leaves at midseason). However, in late July we found out with great disappointment that ISA will not fund the work with corn for the second year, for which we would receive the funding in October. Therefore, we stopped all work with corn. I am trying to find other funding to complete the corn work because one year of data is useless. Work in the soybean trials continues at this time by analyzing about 700 soybean tissue samples and harvesting grain.