Crop Growth Analysis of Autumn- and Spring-Sown Wheat–Pea Intercrops

Intercropping of arable crops might provide yield benefits over monocrops. To assess the effect of sowing date and sowing ratio on biomass formation and competition over time, a two-year field experiment with wheat and pea plants was performed in Eastern Austria with two sowing times (autumn vs. spring) and with the following substitutive wheat–pea sowing ratios (%:%): 100:0, 75:25, 50:50, 25:75, 12.5:87.5 and 0:100. For both crops, facultative cultivars were used. Compared to spring-sowing, autumn-sowing resulted in earlier development of plants, taller plants, faster soil coverage, a higher crop growth rate up to mid-May in the first year and early June in the second year, more above-ground dry matter production and in the second year also in a higher land equivalent ratio (LER) of intercrops. Sowing ratios affected absolute and relative growth rates of wheat and pea plants. Wheat, which was generally the stronger partner in the intercrops, out-competed pea plants in all intercrops in the first year due to a higher early crop growth rate and in the second year, when the monocrop biomass of wheat was lower than that of pea plants, even in the intercrops with lower wheat and higher pea share. All intercrops resulted in a yield advantage compared to the monocrops as indicated by the LER. At final harvest, this yield advantage was over both sowing times and all four intercropping ratios 14% in the first and 10% in the second year. The competitive abilities of individual crops in mixtures, as indicated by the partial LER, were not affected by the sowing time.