You can analyze paired observations of a measurement variable using a paired t –test , if the null hypothesis is that the mean difference between pairs of observations is zero and the differences are normally distributed. If you have a large number of paired observations, you can plot a histogram of the differences to see if they look normally distributed. The paired t –test isn't very sensitive to non-normal data, so the deviation from normality has to be pretty dramatic to make the paired t –test inappropriate.
On behalf of the Potassium Nitrate Association (PNA), Landlab research station in Quinto Vicentino (Italy), conducted a trial to test the effect on winter wheat yield of two foliar applications with potassium nitrate (KNO 3 ) in spring.
The time and placement of foliar application of potassium nitrate caused 17% yield increase even at the highest K level in the base dressing. The foliar application of KNO 3 is promoting a higher yield compared to the untreated entries and the foliar applied K is efficient for increase of yield, mainly due to more ears/m 2 . The yield results are clear and statistically strongly supported at a very high level of confidence.
The study is confirming the benefit of potassium nitrate applied twice as foliar spray, in the key moment of the crop cycle, at 10 kg/ha/application over all four levels of K in the base dressing nutrition.