盐碱地人工栽培枸杞营养元素分配、累积及输出特征

Allocation,accumulation, and output characteristics of nutrient elements of Lycium barbarum grown on secondary saline land

枸杞(Lycium barbarum)是我国干旱地区重要的传统药用植物,也是近年来干旱区盐碱地改良利用中优先选择的经济型灌木,具有改良盐碱地和增加农户经济收入的双重作用。为掌握不同营养元素(碳、氮、磷、硫、钾和灰分)在枸杞植株不同构件(花、果、叶、枝条、主杆和根系)、不同空间层次(地上0—50、50—100、100—150 cm和150—200 cm;地下0—100 cm)的分布特征,在地处干旱地区的甘肃景电灌区,选择盐碱地人工栽培的4年生、7年生和11年生枸杞林,研究了人工栽培枸杞营养元素的分配、累积和输出特征。结果表明,成龄枸杞不同构件营养元素含量显著不同,其中花富含碳、氮、磷和钾,果实富含碳、钾和硫,叶富含碳、硫和灰分,主杆和枝条富含碳,根系富含碳和氮。碳是构成枸杞各构件的最主要元素,在主杆的含量最高,达到44.25%;在叶片的含量最低,但也达到29.8%,占到主杆的67.3%。单株枸杞不同构件和空间层次营养元素的累积量也显著不同。其中,成龄单株枸杞不同构件营养元素的累积总量表现为根系≈主杆>枝条>叶>果实>花,碳是主要累积物质,其累积量所占生物量干重的比例均超过30%;而氮、磷、钾和硫累积量所占生物量干重的比例均在3%以下。成龄单株枸杞不同空间层次营养元素的累积总量在150—200 cm层最少;50—100 cm层最大,是栽培管理的关键层次。成龄枸杞林落叶、果实采收与枝条修剪每年造成大量营养元素输出。植物必须三大营养元素氮、磷和钾在枸杞林的输出量全年累积达到190.4 kg/hm^2,其中果实产生的输出量达到91.1 kg/hm^2,占到全年累积输出量的47.7%;枝条修剪产生的输出量达到23.2 kg/hm^2,占到全年累积输出量的12.2%。上述结果说明枸杞不同构件对不同营养元素的吸收不同,而且每年因果实采收与修剪造成大量营养元素流失。因此,合理施肥对保持枸杞林健康生长以及维持高产量十分关键,而修剪枝的粉碎还田也十分必要。

Lycium barbarum （Wolfberry） is an important traditional medicinal plant that grows in arid areas of China. In recent years, it has been widely cultivated on saline lands not only for its significant economic benefits （ due to the use of its fruit in medicine and health products）, but also for improvements in the saline soil of arid regions. In order to trace the distribution characteristics of the main nutrient elements （ C, N, P, S, K, and ash） in different modules （flowers, fruits,leaves, branches, stems, and roots） and vertical tree layers （ aboveground ： 0--50 cm, 50--100 cm, 100--150 cm, and 150--200 cm; belowground： 0--100 cm） of L. barbarum, 4-, 7-, and ll-year-old L. barbarum plants in their fruiting periods were selected at the Jintai electrical-irrigation area in Gansu Province. The results showed that the contents of C, N, P, K, S, and ash in different modules of adult plants were significantly different. Flowers were rich in C, N, P, and K; fruits in C, K, and S; leaves in C, S, and ash; stems and branches in C; and roots in C and N. C was the most important constituent in all modules of the plant. Its content in the stems reached 44.25%, which was highest among the modules, whereas that in the leaves was the lowest （29.8%） and only accounted for 67.3% of the stems. The accumulative amount of nutrient elements in different modules and vertical tree layers were also significantly different. The order of the total accumulative amount of nutrient elements in different modules was as follows： root 〉 stem 〉 branch 〉 leave 〉 fruit 〉 flower. C, as the major accumulative matter, accounted for more than 30% of dry biomass of the different modules, whereas N, P, K, and S each accounted for less than 3%. Aboveground, the total nutrient elements in the 0-50 cm, 50-100 cm, 100-150 cm, and 150-200 cm layers accounted for 26.9%, 42.3%, 24.5%, and 6.2%, respectively. This indicates that nutrient elements accumulate mainly in the 50-100 cm layer, which is a key layer for management. In addition, defoliation, fruit harvesting, and pruning annually result in the export of large amounts of nutrient elements, and the annual cumulative output of the three essential elements N, P, and K reached 190.4 kg/hm：, of which the output of fruits was 91.1 kg/hm2, accounting for 47.7%, and that of pruned branches was 23.2 kg/ hm2, accounting for 12.2%. The results showed that the different modules of the plant absorb different amounts of nutrient elements, and fruit harvesting and pruning caused significant losses of nutrient elements. In conclusion, rational fertilization is vital for maintaining the growth and high yield of L. barbarum plantations, and it is also essential to return shredded pruned branches to saline lands.