| Green manure has many functions, such as increasing soil nutrients, improving soil properties, reducing fertilization, raising fertilizer use efficiency and so on. Recently,there are large areas of winter fallow field in North China which cause many negative results. Orychophragmus violaceus(L.)O.E.Schulz was introduced as winter green manure, which could mitigate the above-mentioned problems. Orychophragmus violaceus belongs to colewort of cruciferae, which is biennial herbage. This experiment investigated the growth and nutrition characteristics of Orychophragmus violaceus, the effects of fertilization and sowing date on Orychophragmus violaceus, the decomposing and nutrient release pattern of Orychophragmus violaceus in sandy soil and the effects of using Orychophragmus violaceus as winter green manure on spring maize (Zea mays L.). The main results were showed as follows:1.Growth characteristics of Orychophragmus violaceus.Orychophragmus violaceus budded and bolted almost synchronously. Flowering stage and silique mature stage were overlapping during some time. The growth stages of Orychophragmus violaceus could be divided into 6 stages as follows: seeding stage (September 15November 25), winter dormant stage (November 26March 14), returning green stage (March 15 March 26), budding stage (March 27April 14), flowering stage (April 8May 8) and silique mature stage (April 26early June). The flowering stage could be subdivided into early flowering stage (April 8April 17), full flowering stage (April 18April 28) and ending flowering stage (April 29May 8). Orychophragmus violaceus grew slowly at returning green stage; the fresh weight and dry weight increased rapidly at budding stage then reached the maximum at full flowering stage; after full flowering stage, the dry weight increased slowly but the fresh weight decreased rapidly. The plant height reached the maximum in late April; the water content had maintained above 80% from returning green stage to the end of flowering stage.2.Nutrition characteristics of Orychophragmus violaceus.The contents of N and K were high, but P was low in Orychophragmus violaceus. At full flowering stage, the contents of N, P and K were 2.96%, 0.42% and 2.75% respectively. From returning green stage to silique mature stage, N, P and K contents kept decreasing. The accumulation amounts of N and K were large, but P was small. At full flowering stage, the plant had accumulated 86.29%, 93.98% and 86.46% of total N, P, and K respectively. It was the most suitable time to plough the plants into soil from full flowering stage (April 23) to ending flowering stage (May 5).3.Effects of fertilization on Orychophragmus violaceus.Among N, P and K, N showed the greatest influence on fresh grass yield. The biomass could increase significantly by proper nitrogen application. There was the same variation for the nutrient accumulations in fresh grass. The best fertilizer application rates were N 125145 kg/hm2, P2O5 7090 kg/hm2, K2O 4065 kg/hm2.4.Effects of sowing date on Orychophragmus violaceus. Sowing date could influence on growth and development of Orychophragmus violaceus significantly. Sowing late decreased fresh grass yield, nutrient accumulations and seed yield obviously. Under the experimental conditions, the optimal sowing date was in mid-September.5.Decomposing pattern of Orychophragmus violaceus.The decomposing rate of Orychophragmus violaceus was 76.35% after covered in soil for 125 days. The contents of N and K were decreased by 39.52% and 69.72% respectively within 14 days; the content of C was decreased in the first two weeks and changed little later; the content of P was increased first and then decreased quickly; the C/N ratio of Orychophragmus violaceus was increased slowly from 9.74 to 17.82. The nutrient release rates of N, P and K were 88.93%,84.80% and 96.75% respectively. N and K released quickly at the beginning by the rates of 50.01% and 74.47% respectively in the first two weeks; P released slowly at the beginning but quickly later.6.Effects of Orychophragmus violaceus on chemical properties of soil.The contents of soil total N, alkali-hydrolyzable nitrogen, available P and available K were increased after plough Orychophragmus violaceus; the soil pH and C/N ratio were decreased. These effects were more obvious with increasing the application amounts of Orychophragmus violaceus. But the influence on increasing the content of soil organic matter was little.7.Green manure effects of Orychophragmus violaceus.Maize grain yield was increased and fertilizers could be replaced partly by plough Orychophragmus violaceus. Compared with the conventional fertilization, treatments of green manure combined with chemical fertilizers, which were 100%, 85%, 70%, and 40% of the conventional amounts, could increase maize biomasses by 12.44%20.20%, increase maize yields by 3.52%11.52%. The accumulation amounts of N, P and K were increased by 11.06%25.37%, 1.38%27.27%, 41.61%60.00%; the fertilizer recovery efficiencies of N, P and K were increased by 16.18%39.11%, 0.87%15.82%, 57.25%144.34% respectively. The N and P accumulation of maize maintained high rates in late growth stage and the highest accumulation rate of K was increased significantly in all treatments of green manure combined with chemical fertilizers. In this experiment, after combined with green manure, it was best to reduce the chemical fertilizer amounts by 30%. As a result of only 1 year, the effects of yield increase and fertilizer replacement by using Orychophragmus Violaceus as green manure should be studied in-depth through locate experiments in future.
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