城市污泥堆肥对栽培基质保水能力和有效养分的影响

Effects of Sewage Sludge Compost on Available Nutrients and Water Retention Ability of Planting Substrate

盆栽试验表明 ,城市污泥堆肥不仅可以明显提高栽培基质的有效氮、磷含量 ,而且可以增强栽培基质的保水性能和植物的抗旱能力 ,但是栽培基质的萎焉点也随着其用量的增加而增高。因此 ,从保证植物水分供应的角度考虑 ,虽然可以大量地使用城市污泥堆肥 ,但是其用量并不是越多越好 ;当用量超过 75 %时 ,继续增加城市污泥堆肥的比例 ,则植物的吸水能力反而会略有下降。从养分供应和保水性能等角度综合考虑 ,采用经过堆肥化处理的城市污泥作为植物栽培基质 。

Sewage sludge compost is a kind of excellent fertilizer due to its abundant nutrition and organic matter. After composting, the sewage sludge could be sold as a commodity to make profits that could be improved by adding inorganic fertilizer. So land application has become one of the best ways for sewage sludge, especially for the developing countries with limited cultivated lands, expanding land application of sewage sludge is very essential with the precondition of resolution of pathogen, vector, and heavy metal.Lots of studies have being done on the effects of sewage sludge compost on plants and environment. Some researches reported that total N, total P and organic matter of surface soils were enhanced by the application amount of sewage sludge compost. When sewage sludge compost was used as the substrate of container breeding, the chemical and biological properties of soils were improved. Few studies on the effects of sewage sludge compost on water retention ability of planting substrate have been reported by now.In order to study the effects of sewage sludge compost on water retention ability and soil nutrient availability of planting substrate, pot experiment growing wheat was carried out in the greenhouse. Three experimental series were designed as follows: (1) Series I——the growing substrate without plant was incubated for 30 days, and investigated the moisture of growing substrate, available N and P on day 30; (2) Series II——wheat plant was grown for 30 days, and investigated the soil moisture, available N and P on day 30; (3) Series III——wheat plant was grown for 30 days, and the dynamics of the moisture of growing substrate and wilting point of the plant were tested until the wheat went to death due to lacking of water after stopping the irrigation on day 30. Each series consisted of five treatments, i.e., treatment 1 (100% soil), treatment 2 (25% compost + 75% soil), treatment 3 (50% compost + 50% soil), treatment 4 (75% compost + 25% soil), treatment 5 (100% compost). The results showed that the biomass of wheat increased due to more sewage sludge compost was added (R 2 =0.998). The more the compost was used, the higher water retention ability of plant substrate would be. The wilting point of the all treatments with compost was found to range from 78 h in treatment 1 (without compost) to 170~220 h in treatment 3 and 4. From the view of point of the water retention ability of the planting substrate, it was better when the proportion of sewage sludge compost was 50%~75%. According to the simulation, it could be calculated that the maximum time of wilting point was 235h when the proportion of sewage sludge was 77%. It could be concluded that the water retention ability of the substrate could be improved evidently when using sewage sludge compost as plant substrate. When the proportion of sewage sludge compost was appropriate, the wheat plant could survive for 10 days without irrigation. It is indicated that sewage sludge compost could improve the drought-resistant ability of plant due to the evaporation of water of substrate was reduced. The manpower of irrigation could be reduced if sewage sludge compost was used as a plant substrate in agricultural and horticultural production. Although more than 91% nitrogen of sewage sludge compost is organic nitrogen, it could evidently enhance available nitrogen of the growing substrate in all treatments with or without plant. The available nitrogen was found to be positively correlated to the application rate of sewage sludge compost. Not only did sewage sludge compost provide nitrogen that was necessary for plant, but also enhanced the available nitrogen of planting substrate. Similar trends were also found in available phosphorus. Using sewage sludge compost as planting substrate could provide nitrogen and phosphorus for plant and enhanced the available nitrogen and phosphorus of planting substrate. Considering the nutrient supply and water retention ability, utilization of sewage sludge compost as planting substrate is feasible way to reuse and dis