摘要
Intercropping is the cultivation of more than one crop species on a single parcel of land. Intercropping seeks toexploit species complementarities to capture more of the available light, water and nutrient resources, and thusincrease combined crop yield[1]. Intercropping is well known in China, where smallholder farmers practice a greatdiversity of species combinations to increase their yields[2]. Figure 1 illustrates intercropping as done by a farmer inGansu Province, China, who chose to combine wheat, soybean and maize. This three-way combination offersseveral species complementarities. First, the growing period of wheat ends earlier than that of soybean and maize,so the soybean and maize can use all the light, water and nutrient resources of the land after wheat harvest. With thewheat covering only around half of the area, the plants will still produce about 70% of the normal yield for wheatgrown as a sole crop, because the wheat has virtually no competition for resources early on, resulting in greatercapture of light, water and nutrient resources in the intercrop than in a sole crop[3]. Furthermore, soybean and maizehave a complementarity for nitrogen acquisition, with maize requiring nitrogen from soil, but soybean being able to fixit from the air. Therefore, this combination can reduce fertilizer requirements.
