A meta-analysis of relative crop yields in cereal/legume mixtures suggests options for management

Abstract

Intercrops of cereals and legumes are grown worldwide, both in smallholder agriculture in developing countries and in organic farming systems in developed countries. The competitive balance between species is a key factor determining productivity in mixtures. Management factors, e.g. sowing time, sowing density and rate of N fertilizer, affect the relative competitiveness and performance of intercropped species. There is a need for an overarching analysis to elucidate general principles governing the relative performance of legumes and cereals in mixtures. We therefore conducted a meta-analysis of published studies to explore how the relative yield of legumes and cereals in mixtures responds to relative sowing time, relative density and nitrogen fertilizer. An index for relative sowing time, RST, was developed to quantify the relative difference in sowing time between the intercropped species. RST is defined as the amount of time that a species is sown earlier or later than its companion species, relative to the length of its own growing period. RST is smaller than zero if a species is sown earlier than its companion species and greater than zero if it is sown later. Relative performance of a species was characterized by its relative yield (or partial land equivalent ratio, PLER) in the intercrop compared to the yield in the sole crop. In 409 out of 552 cases, the cereal had a greater relative yield than the legume. Sowing a species earlier than its companion increased its relative yield, and vice versa. An increase in density of a species increased its relative yield and decreased the relative yield of the companion species. The relative yield of cereals increased and that of legumes decreased with the amount of N fertilizer. The negative effect of N on the relative yield of legumes was mitigated if the legume was sown before the cereal. The study shows how the performance of cereals and legumes in an intercrop is affected by sowing densities, relative sowing times, and nitrogen fertilizer. Growers can 3 exploit these relationships to manage competition between cereals and legumes in mixtures and enhance species complementarity, total productivity and economic profit.

Agronomic and Economic Benefits of Pea/Maize Intercropping Systems in Relation to N Fertilizer and Maize Density

“…Legume/cereal intercropping has been broadly practiced in many short-season areas, such as the northern Great Plains of Latin America, North America, northwest Eurasia and northwest China where the temperatures only permit one crop per year [1][2][3]. The advantages of legume/cereal intercrops are often assumed to arise from the complementary use of N sources by intercropping with legumes, because intercropped legumes can meet their N demand due to the complementarities between symbiotic N 2 fixation, soil N acquisition and intercropped cereals uptake of more N from the soil than they stand in sole cropping [4][5][6].…”

Wheat Growth Is Stimulated by Interspecific Competition after Faba Bean Attains Its Maximum Growth Rate

“…Better growth and yield were achieved when a nonlegume crop was intercropped with a legume crop (Yu et al, 2016). However, the facilitation was modulated by field N and P conditions.…”

“…A similar result was found in this study (i.e., wheat yield increased when wheat was intercropped with faba bean, but intercropping decreased faba bean yield; Table 1). In short, crop management, including sowing time (Yu et al, 2016), row ratio (Surve and Arvadia, 2012), row spacing (Campiglia et al, 2014), and fertilization and sowing density (Pelzer et al, 2016), and climatic condition such as solar radiation, precipitation, and temperature (Harris et al, 2007;Brainard et al, 2011) are highly related to yield performances in intercropped systems. Similarly, other research illustrated that cereal could improve legume yield by increasing Fe availability (Zuo et al, 2004).…”

Yield and nitrogen uptake of sole and intercropped maize and peanut in response to N fertilizer input

“…Intercropping is defined as the cultivation of two or more crop species in the same field for the whole or a part of their growing period (Li, Zhang, & Zhang, ; Li, Zhang, Ma, et al, ). Intercropping contributes to high yields and high land use efficiency due to complementarity in resource requirements between plant species (Franco, King, & Volder, ; Yu, Stomph, Makowski, Zhang, & Werf, ). This complementarity enables a better overall capture of resources (Gou et al, ; Zhang et al, , ).…”