Root‐and‐shoot growth and yield of different grass–clover mixtures

Abstract

The effect of different grass–clover mixtures on yield, root biomass, root length and the symbiotically fixed N quantity was investigated in a two‐factorial field experiment at a location in Freising (Germany). Three grass–clover mixtures with different compositions were tested in two different management systems (various harvest and mulching): a standard mixture (SM) consisting of 40% legumes and 60% grass; a multi‐species legume–grass mixture suitable for forage use (FM) and a mixture adapted for green manure (GM) with a high share of legumes (70%) and herbs (5%). The botanical composition shifted in favour of the amount of grass in mulching variants. Certain herbs managed to do well in the mixtures despite intensive management with four cuts. Grass–clover mixtures with herbs and legumes achieved high shoot yields (15.9–16.5 t ha−1). Due to its lower share of grass, GM showed the smallest root length (95 km m−2). FM and SM achieved a length of 130 km m−2 (depth: 0–30 cm). The measurement of root biomass gave high dry matter yields (FM 8.1 t ha−1, GM 6.5 t ha−1, SM 5.3 t ha−1). N uptake depended on the share of legumes and on the management system. The amount of symbiotically fixed nitrogen that accumulated in shoots and roots was about 90 kg N ha−1 (SM), 290 kg N ha−1 (FM) and 340 kg N ha−1 (GM). The C input was increased by mulching systems and a high root biomass. FM has shown possibilities for optimizing grass–clover mixtures with respect to the root parameters, effects on soil fertility and increasing C input without a decline in yield. The rooting patterns can be used to compose grass–clover mixtures with a higher root biomass and root penetration.