Maize-Brachiaria grass intercropping: A meta-analysis of major productivity drivers in Brazil

Abstract

Context or problemIncreasing crop intensification while enhancing soil conservation is an important aspect of global food security. Intercropping (syn. interseeding) between cash crops and tropical forages improves soil cover, prevents soil erosion, and enhances land use via crop and livestock integration. In Brazil, intercropping between maize (Zea mays L.) and Brachiaria grass (Urochloa spp.) is the most commonly adopted system, with opportunities for expansion across tropical and subtropical landscapes worldwide. Nonetheless, there is little consensus on the effects of intercropping on the performance of each individual crop species. Objective or research questionA meta-analysis was conducted to quantify the effect of intercropping on maize grain yield and Brachiaria grass biomass production and to understand the impact of environmental and management factors on intercropping performance. MethodsA literature search was conducted to retrieve peer-reviewed studies carried out on this intercropping system under field conditions. Manuscripts were scrutinized and included in this meta-analysis when they met the following criteria: i) data on maize grain yield and Brachiaria grass biomass under intercropping were reported, ii) inclusion of a control treatment (monocropping) for at least one species, and iii) field trials with at least three randomized replications. Our database included 429 data points extracted from 56 published manuscripts from all regions of Brazil. ResultsRelative to monocropping, intercropping reduced maize grain yield (−5.6 %) and Brachiaria grass biomass production (−64 %) in all scenarios. The intercropped maize grain yield was less affected under the following conditions: i) in the subtropical climate zone (−3.6 %), ii) sowing the intercrop early in the season (−5.8 %), iii) applying monocot-selective postemergence herbicides (−4.4 %), iv) relay temporal arrangement (−2.8 %), and v) with N and P fertilization rates above 150 and 35 kg ha-1, respectively. In relative terms, Brachiaria grass performance was more affected by i) intercropping adoption, with a reduced biomass penalty under a tropical climate (−63.9 %), ii) late sowing time for the intercrop (−59.5 %), iii) application of N fertilizer at a rate above 50 kg ha-1 (−70.5 %), and iv) non-use of postemergence herbicides (−21.9 %). ConclusionMaize-Brachiaria grass intercropping was an effective alternative to produce residue (no-till system adoption) or forage (crop-livestock integrated system adoption) with reduced maize grain yield penalties, diversifying cropping systems in Brazil. Implications or significanceDespite the production penalties for both crop species, considering different relative values, specific management practices and climate conditions could minimize yield penalties. Scenarios favoring maize yields may be preferred for intercropping systems focused on improving soil quality; in contrast, Brachiaria grass biomass may benefit the integration of crop-livestock systems focused on ensuring forage production.