Nitrogen Conservation With Cover Crops: Effect Of Cn Ratio And N Losses Over Winter On The Potential To Supply Succeeding Crops

Summary

A field trial with different cover crops was carried out in 2018 in Hennef, Germany, to clarify the fate of plant nitrogen over winter. High amounts of nitrogen (up to 100 kg ha-1) were taken up by aboveground plant biomass before winter. Nitrate leaching was avoided in a large scale compared to the untreated control. After winter 10 to 55 % of shoot nitrogen were lost with the highest decline in legumes and the lowest in crucifers. If mulched, losses raised up to 90 %, e.g. for narrow-leaved lupin. Nitrogen losses were slightly lower, when mulch was incorporated by rotary tilling. The CN ratio in stems became wider after winter. Only in leaves the CN ratio was narrow enough to cause an effect on nitrogen supply to the succeeding crop. A trend to higher soil mineral N in spring was only noted in treatments with frost hardy cover crops.