Soil Nutrient Accumulation Properties And Fertilization Effects In Newly-Built Solar Greenhouse

Solar greenhouses, being a special facility cultivation technology in China, make itpossible to produce vegetables during the winter without additional heating and lighting inlarge parts of northern China. Due to its remarkable economic and social benefits, this systemhas become the mainstay industry in some regions in north China. However, the phenomenonof overuse of fertilizer and manure in greenhouse system is serious, which gives rise to aseries of problems accordingly. These issues deeply influence the production benefits of thissystem and its sustainable development. Therefore, investigating vegetable fertilizermanagement, soil nutrient balances and accumulation properties in solar greenhouse is criticalin theory and practice for building up scientific nutrient management system in solargreenhouse, promoting the sustainable development of this planting system and fulfilling theeconomic, ecological and social benefits.At present, most research about the soil nutrient accumulation properties concentrate onthe old greenhouses, and little research is conducted on newly-built greenhouse. So, we chosethe newly-built solar greenhouses in Yangling, Shaanxi province as research object. Thisstudy was carried out to investigate the soil nutrient balances and accumulation properties fornewly-built solar greenhouse through surveying fertilization status and measuring soilproperties over two years, and compare the effects of different fertilization treatments ontomato yield and soil nutrient balances through greenhouse fertilizer experiment. The mainresults were as follows:1.165newly-built greenhouses were surveyed over two consecutive years. The resultsindicated that farmers applied manure and inorganic fertilizers at average annual rates of1776kg N ha^-1,1507kg P2O5ha^-1and1614kg K₂O ha^-1. Manure was the main source of nutrient innewly-built greenhouse, which accounted for65%of the total N input,58%of the total Pinput and56%of the total K input. The annual nutrient input rates were much greater than thecrop required. The average annual apparent nutrient surpluses were1313kg N ha^-1,1395kgP₂O₅ha-1and880kg K₂O ha^-1, which were equivalent to289%of the N uptake,1275%of theP uptake and122%of the K uptake. 2.13newly-built greenhouses were chose to investigate the soil nutrient accumulationproperties over two years. The results indicated that soil organic matter, total N, available P,available K and electrical conductivity （EC） increased significantly over two years in thetopsoil （0-20cm depth）, which increased by100%,107%,948%,98%and84%, respectively.Soil available P increased exponentially over two years. By contrast, little change took placein the subsoil （20-100cm depth）.3. The nitrate-N concentrations （mg N kg^-1） of the0-100cm depth increased by163%-336%over two years, with the biggest increase rate maintaining in the topsoil. Theaverage nitrate-N content （kg N ha^-1） of the0-100cm depth increased by241%over twoyears and leveled out at511kg N ha^-1, with the largest value of1085kg N ha^-1. The nitrate-Ncontent of the0-200cm depth averaged1015kg N ha^-1, with the largest value of1767kg Nha^-1. In conclusion, over-fertilization led to large nutrient surpluses in the soil of newly-builtgreenhouses.4. The results of field experiment over two years indicated that, in comparison with theconventional fertilization treatment, the yields of tomato for formula fertilization treatmentsdid not significantly decrease when the rates of N, P, and K inorganic fertilizer applied weredecreased by12%-45%,39%-55%and19%-47%, respectively; it indicated theover-application of fertilizer for conventional fertilization treatment. Reducing the use ofinorganic fertilizer could mitigate the accumulation of soil available nutrients to some extent.