目标:自古以来在美洲,玉米,豆子和南瓜在被称为“三姐妹”的多元文化中一起种植。在土地当量基础上,这种混种及其玉米/豆变体的产量高于成分单种。这项研究表明,地下生态位互补性可能有助于这种产量优势。
方法:玉米的单一栽培和多重栽培,豆和南瓜在氮(N)和磷(P)利用率不同的田地中生长了两个季节。使用改良的基于DNA的技术来区分不同物种的根,从而确定了单个作物和整个多培养物的根生长模式。
结果:在土地当量基础上,玉米/豆/南瓜和玉米/豆的混培比单一栽培具有更高的产量和生物量产量。生物量产量的增加主要是由互补效应而不是选择效应引起的。“三个姐妹”的组成部分之间的根冠结构和垂直根分布的差异表明,这些物种具有不同的,可能是互补的,营养觅食策略。玉米觅食相对较浅,普通豆更平等地探索了垂直土壤剖面,南瓜的根部位置取决于P的可用性。在多培养物中,所有物种的侧根分枝密度均显着大于单种。
结论:可以得出结论,根系觅食策略中的物种差异增加了土壤勘探总量,从而对这些古老的多元文化的生长和产量产生积极影响。
OBJECTIVE: Since ancient times in the Americas, maize,
bean and squash have been grown together in a polyculture known as the \'three sisters\'. This polyculture and its maize/
bean variant have greater yield than component monocultures on a land-equivalent basis. This study shows that below-ground niche complementarity may contribute to this yield advantage.
METHODS: Monocultures and polycultures of maize,
bean and squash were grown in two seasons in field plots differing in nitrogen (N) and phosphorus (P) availability. Root growth patterns of individual crops and entire polycultures were determined using a modified DNA-based technique to discriminate roots of different species.
RESULTS: The maize/
bean/squash and maize/
bean polycultures had greater yield and biomass production on a land-equivalent basis than the monocultures. Increased biomass production was largely caused by a complementarity effect rather than a selection effect. The differences in root crown architecture and vertical root distribution among the components of the \'three sisters\' suggest that these species have different, possibly complementary, nutrient foraging strategies. Maize foraged relatively shallower, common
bean explored the vertical soil profile more equally, while the root placement of squash depended on P availability. The density of lateral root branching was significantly greater for all species in the polycultures than in the monocultures.
CONCLUSIONS: It is concluded that species differences in root foraging strategies increase total soil exploration, with consequent positive effects on the growth and yield of these ancient polycultures.