摘要
Sulphur (S) cycling and implications on S fertilizer requirement in sheep-grazed pastures receiving three levels of S fertilizer at rates of 0, 30 and 60 kg S/hm 2 in 1995 and 1996 were studied using a mass-balance approach which accounted both for S inputs to and outputs from the soil-plant-animal system. Results indicated that S fertilizer increased by 50% of herbage S uptake and 15% or more of S bio-cycling rate in grazing system. The total S recovery of 30 and 60 kg S/hm 2 treatments from 1995 to 1996 was 74.0% and 37.6% respectively. Mineralization of organic S may be an important source of S for pasture when other S sources are low, accounted for 70% of the total S inputs without S fertilizer. The grazing sheep has an important ecological function, the feature of S cycling in grazed pastures was that 90% of herbage S ingested by grazing sheep was returned to soils as excreta. The amount of S released by sheep excreta accounted about 30% of the total released S through S bio-recycling. Loss from soil S leaching beyond the major plant rooting zone was the main S output from grazing system. However, urinary and fecal S losses, including transfer and leaching losses, also affected S budgets of grazing system. It is therefore important to investigate the recycling rate of both urinary and fecal S under field conditions. Based on the mass-balance principle, at least 10 kg S/hm 2 per year may be necessary for sustainable development of grazing system.
应用总体平衡（mass-balance)法研究了施硫肥（0，30及60kgS/hm^2)对内蒙古典型草原放牧生态系统硫循环的影响及在硫肥需要量上的应用，结果表明，施硫肥使牧草硫的吸收量提高了50%，并使放牧系统硫的生物循环速率提高了15%以上，1995和1996年两年内两种硫肥处理30和60kgS/hm^2的硫的利用效率分别为74.0%和37.6%，当其他硫的来源较低时，土壤中有机硫的矿化是草原有效硫的主要来源，约占整个有效硫输入量按劳取酬0%，放牧家畜在物质循环中具有重要的生态功能，其硫采食量的90%左右以排泄物的形式返回到土壤，经过排泄物而释放的有效硫量约占硫的生物再循环量的30%，土壤中硫的淋溶损失是放牧系统中硫的主要输出形式；同时，家畜尿和粪中硫的损失（包括转移到非生产区和淋溶损失）也影响着放牧系统硫的平衡状况，因此，应该深入研究粪尿硫的再循环速率及其影响因素，基于总体平衡原则，该地区放牧系统中至少每年应施入10kgS/hm^2才能保持有效硫的平衡状态。
基金
国家重点基础研究项目 (G2 0 0 0 0 186 0 3)
国家自然科学基金 ( 3990 0 10 3)
中德农业部合作项目 (C12 96 3 1)~~
