Motivating effect of different dairy manure addition on soil initial fertility formation and ryegrass growth in coastal mudflat soil

【Objectives】 Costal mudflats belong to the seashore saline soil family and are characterized by high salinity, low degree of development, inferior structure and low fertility. The increasing mudflats can act as an important land reservoir to mitigate the shrinking of agricultural land. Exploitation and amendment of mudflats have been widely concerned. This experiment was conducted to investigate short-term effects of dairy manure application(DMA)on initial fertility motivation and green manure plant ryegrass growth in a newly-reclaimed mudflat. 【Methods】Using ryegrass as an indicator plant, a field experiment of complete randomized block(RCB)design with three replicates was carried out in a newly reclaimed mudflat. Five rates of dairy manure(0, 30, 75, 150 and 300 t/hm2)were designed. Soil and ryegrass were sampled 60 days after the sowing, salinity the soil pH and the contents of water stable aggregate in different sizes, and organic carbon, the contents of N and P in mudflat soil and ryegrass biomass were measured. 【Results】 The contents of water stable aggregate 0.25 mm in 0-10 cm and 10-20 cm layers of mudflat were increased with the increase of manure addition, and the increments were significant in the treatments of 150 and 300 t/hm2, compared with the control. With the manure addition of 30, 75, 150 and 300 t/hm2, the organic carbon were increased by 17.4%, 32.6%, 55.0% and 205.8%, respectively, the salinity decreased by 25.2%,75.8%,76.0%,75.9%, the pH was not decreased significantly. With the increase of dairy manure addition, the soil total nitrogen, total phosphorus, alkali-hydrolyzable nitrogen and available phosphorus were increased as well. Both the dry weights of aboveground and root part of ryegrass were enhanced with the increased amount of manure, and the increments in ryegrass height were 52.6%, 46.1%, 74.2% and 56.2% at the DMA rates of 30, 75, 150 and 300 t/hm2, respectively. The root length, root average diameter, root surface area and root volume of ryegrass were increased in the same trends. 【Conclusions】 Based on the results of this study, addition of dairy manure could improve the soil ventilation, decrease soil pH and improve the nutrient contents, so can be used as the fertility motivator in soils like coastal mudflat. As the use of dairy manure also provides an ecologically sound way of the disposal of dairy farm wastes, this results is prospective in the amelioration of coastal mudflat.