NIRS as a fast screening technique for total nutrients in strawberry leaves and in spent growing media

The first aim is to test the potential of NIRS to forecast the nutrient concentrations in strawberry leaves, which would then allow for assessing the total nutrient uptake by strawberries. A database with 272 strawberry leaf samples with known concentrations of N, P, K, Ca, Mg, Fe, Mn and Na on dry matter (DM) was scanned with near-infrared reflectance spectroscopy (NIRS). These samples originated from different trials in variable conditions, with different growing media blends and a range of fertilizer types and doses. As a result, the database covered a range of leaf concentrations of 0.6-3.5%N/DM, 0.7-6.3 g P kg^‑1 DM and 2-29 g K kg^‑1 DM. The calibration test indicated the potential for this application, with R² values of 0.90 or higher for N, K, Ca and Mg concentrations in the leaves. The second aim is to test NIRS for assessing the composition and basic characteristics of spent growing media, including the total nutrient content. The first test with 218 compost samples indicated the potential for this application, with R² values of 0.90 or higher for organic matter, EC and total N, and with R² values of 0.85 or higher for total P and K content, C/N and biochemical composition. Focus is on assessing the use of the compost calibration data set for screening of nutrient concentrations in spent growing media.