The article presents results of research on the bulk and shaken density of two commercial fertilizers: Pulgran urea and universal nitrogen fertilizer Salmag. A statistical analysis of the obtained results of average density at the assumed level of significance proved a significant difference between shaken and bulk density investigated with the use of Engelsmann apparatus and shaken density tested with a laboratory shaker for both investigated fertilizers. The obtained test results and uncertainty of the measured values served for calculation of uncertainty of the standard complex bulk and shaken density determined in case of many uncertainties. Further, an analysis of the impact of error sources on the value of complex uncertainty was conducted. The final results of the measurement were presented according to the convention of the Central Office of Measures.
Three different types of nozzles (different wear rate) were used in this study. They are classified depending on the severity of their wear to three groups: new, worn and damaged nozzles. Those nozzles were spraying with the same application rate (303 l/ha) on two-year field trials; this was achieved by changing the spraying pressure for each group of nozzles in order to get the same application rate. This practice is usually done by operators of sprayers, who calibrate the sprayers on the same application rate every year without changing the nozzles, so they tend to reduce the spraying pressure in order to compensate the flow rate increase due to the nozzles yearly wear. Two types of plant growth regulators (PGR) agents were used in this study, namely: Moddus and Kelpak, they were applied to wheat plants field to reduce lodging. The results showed that applying PGR in the year 2015 produced an increase in the wheat yield and reduction in the plant height regardless the nozzle type, although there was not any occurrence of wheat lodging. In the year 2016, the new nozzles produced higher values of wheat yield than other two types of nozzles.
Two tests were carried out to measure the standard flat fan nozzles wear during a specific period of an accelerated wear procedure. The first test aimed at getting 10% increase in the flow rate compared to the nominal flow rate, which is the threshold to replace the nozzles according to the nozzles testing standards. The second test was to wear the nozzles intensively (100 hours of accelerated wear), which represents the use of nozzles beyond the allowed threshold. The results showed that the flow rate reached 1.31 l·min−1 (equal to 10% increase) for the tested nozzles after 35 hours of the wear test. For the second test, the 10% increase of the flow rate was reached after approximately 30 hours. The wear rate reached 27.5% at the end of the test and this is 2.7 times more than the standardized threshold.