Assimilation capacity by non-destructive in situ measurements in longterm experiment of maize (Zea mays L.) under different plant density and nitrigen supply in Chernozem

We conducted a long term experiment (set up in 1983) to examine the effects of fertilization and plant density on SPAD and LAI values as well as yield in 2017 and 2018, in two maize hybrids (Sushi, Fornad) in chernozem soil. Hybrid yields varied between 10.2– 16.7 t ha-1 in 2017 and between 9.3–15.9 t ha-1 in 2018, depending on fertilization doses and plant density. The hybrids had SPADmax values in early July (55.5–60.4 in 2017 and 54.9–63.9 in 2018), whereas they got LAImax values in early July (3.0–5.3 m2 m-2 in 2017) and early August (3.5–4.4 m2 m-2 in 2018). Research data evaluated by Pearson correlation calculations proved that fertilization was the main factor that had a significant effect on SPAD and LAI values in the different maize phenophases (r = 0.6**–0.8** for SPAD, r = 0.5**–0.8** for LAI). Correlation among plant density, hybrid and SPAD and LAI values showed very weak correlations in both years (r = 0.1–0.3). The yield of the maize hybrids was most significantly affected by fertilizer in 2017 (r = 0.672**) and plant density in 2018 (r = 0.517**).