Nutrient Load in Runoff from Small Plots: Laboratory and Field Rainfall Simulation Tests on Chinese Loess Soils

摘要

Due to severe soil erosion the fertility of the soils of the Chinese loess plateau decreases. Together with the sediment also nutrients are lost. Near Luoyang (Henan province, China) field plots were constructed to measure nutrient and soil losses under different tillage practices. In addition to the measurements under natural rainfall conditions, rainfall simulations were carried out on bare soil on the field and in the laboratory. Rainfall simulations in the lab were used to correlate nutrient losses to sediment losses. The average enrichment ratios of phosphorus, organic carbon and CaCO_3 varied between 1 and 1.3. The influence of the unit sediment load on the enrichment values was limited. Similar values were found for the rainfall simulations on the field. In the beginning of the rainfall simulation a preferential transport of fine particles took place, but after 30 minutes the clay enrichment ratio decreased towards 1. Nutrient analyses of the runoff from the field plots under natural rain indicated much higher enrichment ratios for organic carbon and available phosphorus. Possibly these values are due to application of P fertilizer, but additional field measurements have to confirm this.