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在大平原南部地区,雨量不足和分布不均是限制作物生产的主要因素.特别是单种或复种的夏季作物尤为如此.本研究是于1976-1987年在俄克拉何马的Bixby植物研究站进行的,试验地为粉砂壤土(Gumulic Haplaquclls).目的是测定雨养条件下同一块地里小麦、大豆和粒用高粱长期复种对维持籽粒产量的效应.12年的单作小麦平均产量为3050kg/ha,而与大豆和粒用高粱复种的小麦产量分别为2510kg/ha和2450kg/ha.12年中有11年,采取常规耕作单种大豆和粒用高粱及麦后免耕复种大豆和粒用高梁.单种大豆的平均产量为2470kg/ha,而免耕复种的产量为1930kg/ha;单种粒用高粱的平均产量为5130kg/ha,而免耕复种的产量为4200kg/ha.在降雨量接近30年平均雨量及其分布的那些年份(11年中有5年),复种大豆和粒用高粱的产量与单种产量不相上下.这些结果表明,小麦、大豆和粒用高粱复种的产量可以长期维持.在俄克拉何马东部地区,中等质地土壤中复种比单种能更有效地利用气候、土地、劳力和设备等资源,从而获得更高的籽粒总产量.
In the southern part of the Great Plains, low rainfall and uneven distribution are the main limiting factors on crop production, especially single or multiple crops.This study was conducted at the Bixby Botanical Research Station in Oklahoma from 1976 to 1987 For the purpose of determining the effect of long-term multiple cropping of wheat, soybean and grain sorghum on the maintenance of grain yield in the same land under rainfed conditions.The average 12-year single-crop yield was 3050kg / ha, while the wheat yield with soybean and grain sorghum was 2510kg / ha and 2450kg / ha respectively in the middle of the year of eleven years. Conventional tillage soybean and grain with no-tillage soybean and sorghum The average yield of single sorghum was 2470kg / ha, while that of no-till seed multiplication was 1930kg / ha; that of single sorghum was 5130kg / ha and that of no-till double cropping was 4200kg / ha. In those years (5 years in 11 years) where rainfall was close to the 30-year average rainfall and its distribution, the yields of multiple crop and sorghum were comparable to those of single crops.These results showed that wheat, soybean and grain sorghum Multiple crop production can be maintained over the long term. Oklahoma eastern region, medium texture soil revaccination than a single more efficient use of resources, climate, land, labor and equipment, resulting in higher grain production.