Forage quality in cereal/legume intercropping: A meta-analysis

Meta-analyses have highlighted several advantages of cereal/legume intercropping for food compared to sole cropping, but none report on fodder quality and yield. In forage production, mixtures may more effectively balance fiber and crude protein concentrations of the forage in view of nutrient requirements of ruminants than sole crops. However, productivity, quality and the trade-off between these in cereal/legume intercropping of fodder species have not been systematically reviewed. This paper reports on a meta-analysis of a database of global literature on intercropping of forage-producing cereal and legume crops to evaluate the effect of intercropping on dry matter (DM), crude protein (CP), acid detergent fiber (ADF), neutral detergent fiber (NDF), non-CP non-NDF yields and concentrations of intercrops as compared with the respective sole crops. A literature search was carried in Web of Science searching in ‘all fields’ with as search terms: (intercrop* OR “mixed crop*” OR “crop mix* ” OR “mixed cultivation*” OR “polyculture*” OR “row crop*”) AND (forage OR fodder) AND (quality OR "nutri* content" OR "nutri* concentration" OR "nutri* value"). Out of the 759 papers further selection yielded a database based on 61 publications on cereal/legume intercropping reporting total biomass and at least one quality component for both sole crops and their intercrops. The net effects for DM (1.76 ± 0.38 Mg/ha), CP (0.20 ± 0.05 Mg/ha), NDF (1.01 ± 0.25 Mg/ha), ADF (0.63 ± 0.15 Mg/ha) and non-CP non-NDF (0.76 ± 0.22 Mg/ha) yields showed production of all increased upon intercropping. The difference in relative increase in total DM and the four components did not lead to any change in %CP, %NDF, %ADF and %non-CP non-NDF. The change in DM yield was due to enhanced cereal yield. Moreover, the cereal %CP in the intercrops was higher than expected and the cereal %NDF and %ADF in the intercrops was lower than expected, while the overall quality of the legume in the intercrops did not change. Intercropping cereal and legume species will neither improve nor reduce the quality of produced feed, but it makes more effective use of the land through a higher production per unit area. This study reports the combined forage quality and quantity in cereal/legume intercropping. The quantity/quality balance of forage production with cereal/legume intercrops is necessary to design intercropping for forage production. The results can be utilized to establish cereal/legume intercropping systems with different forage production aims.