Advantages intercropping

EVALUATION OF YIELD ADVANTAGE INDEXES IN CARROT-LETTUCE INTERCROPPING SYSTEMS
Francisco Bezerra Neto, Eliane Gonçalves Gomes, Rychardson Rocha de Araújo, Eliane Queiroga de Oliveira, Glauber Henrique de Sousa Nunes, Leilson Costa Grangeiro and Celicina Maria da Silveira Borges Azevedo
SUMMARY The aim of this study was to estimate the effect of the association between carrot and lettuce crops inseveral intercropping systems through different yield advantage indexes, as well as to assess which system is better for the environmental resources management with respect to productivity and economic indicators. A ‘group balanced block’ experimental design was used, with four replications. Cultivars of lettuce crispleaf (‘Lucy Brown’, ‘Tainá’, ‘Laurel’ and ‘Verônica’) and looseleaf (‘Babá deVerão’, ‘Maravilha das Quatro Estações’, ‘Elisa’ and ‘Carolina’) groups were evaluated in intercropping systems with ‘Alvorada’ and ‘Brasilia’ carrot cultivars. The land equivalent ratio (LER) and yield efficiency index (YEI) were estimated, besides economic indicators such as gross (GI) and net (NI) income, modified monetary advantage (MMA), return rate (RR) and profit margin (PM). The evaluatedindexes showed that carrot is the dominant and lettuce the dominated crop. Higher biological/agronomic efficiency indexes and economic indicators were observed in intercropping systems with ‘Brasilia’ carrot as component crop and that based on the crispleaf lettuce group.

Introduction The use of intercropping systems has been one of the strategies used by producers in order to reach highproductivity and promote sustainability of their agricultural production systems. The main given reason for the utilization of these systems is that they enable efficiency increase in the use of the environment resources (Park et al., 2002). As a consequence, an increase in the total biological productivity per area unit of land and in sustainability occurs. Recently, the interest in cropping systems withcrop associations involving vegetables has received more attention; these associations have contributed to an increase in the vegetable

activity, especially because of the economic advantages, due to the intensive use of renewable or non-renewable resources (Cecílio Filho and May, 2002). The efficiency and the advantage of an intercropping system are fundamentally dependent of thecomplementarities between the component crops. In ecological terms, complementarities minimize the overlap of niches among associated species, reducing competition. When the period of greater demand for environmental resources by the component crops is not coincident, competition among such crops can be minimized. This situation can be named as temporal complementarity (Montezano and Peil, 2006).

On theother hand, when differences in plant architecture of the component crops help a better utilization of the available resources, or when biochemical differences exist among crops in their response to environmental resources, spatial or physiological complementarity occurs (Liebman, 2002). Several factors, such as competition among crops, type of sowed cultivar and spatial arrangement of planting, canhave a significant impact in yield and growth rate of component crops in the intercrop (Dima et al., 2007). Lettuce and carrot are examples of vegetables that can be combined, due to biological, nutritional, economic and social reasons, representing an alternative for food produc-

tion and income (Oliveira et al, 2005a, b; Barros Júnior et al., 2005; Bezerra Neto et al., 2005a, b). With thedevelopment of new lettuce and carrot cultivars and their adaptation to the northeastern Brazil conditions, information is needed concerning competition indexes and advantage indicators of the systems, and comparative data about the behavior of the materials used in the intercropped agro-systems is required. Several indexes have been developed in order to quantify competition and agro-economic...