Root Distribution in Additive and Substitutive Pea-Oat Intercropping using FTIR-Spectroscopy for Species Discrimination

Legume-cereal intercropping often shows higher yields and effective resources use compared to sole crops. The different rooting system of legumes and cereals could lead to higher resource efficiency in the intercropping. To study species specific rooting patterns, the roots have to be distinguished according to species. We used Fourier Transform Infrared (FTIR) spectroscopy to determine species specific root biomass in the intercropping.

In a field trial (2013 and 2014, block design, four replicates), the root biomass of pea and oat in pure stands and in three intercrops were recorded. Additive and substitutive sowing designs were investigated: pure stands of pea, cultivar Santana, pure stands of oat, cultivar KWS Contender, intercrops with 100 % pea and 20 % oat (100/20), 100 % pea and 50 % oat (100/50), and a mixture with 50 % pea and 50 % oat (50/50). Root biomass was collected by root auger on and between the sowing rows down to 90 cm soil depths. Dried and ground roots were measured by FTIR spectroscopy. Relative yield (RY) and relative yield total (RYT) regarding root biomass were calculated to detect overyielding. Root spectra showed species specific peaks, clearly separated by cluster analysis, and were used for a quantification model to identify species proportion in the intercrops.

Total root biomass was highest in pure stand of oat and lowest in pure stand of pea in both years. Pea and oat root systems intermingled in the mixtures. Oat roots were found mainly under oat rows, but up to 17 % also under pea rows. The same is true for pea roots. RYT of roots were above 1 in all mixtures in 2013, but only in mixture 50/50 in 2014. RY of pea was above 0.5 in all mixtures; RY of oat only in mixture 50/50.