Effects Of Nitrogen Deposition On Agroecosystem Of Curcuma Aromatica Cv. Wenyujin

A simulated nitrogen deposition experiment was conducted in the agroecosystem of Curcuma aromatica cv. Wenyujin.Treatments were designed as CK(0 kg Nï¹’hm-2a-1),T50(50 kg Nï¹’hm-2a-1),T100(100 kg Nï¹’hm-2a-1) and T150(150 kg Nï¹’hm-2a-1). The results were as follows.1 Effects of nitrogen deposition on physiological ecology of C. aromatica 1)Elevated nitrogen deposition increases basal stem diameter and height of C. aromatic and enhances length,width and area of leaf, but has no effects on length-width ratio and leaf number.Nitrogen deposition can contribute to the growth of the roots of C. aromatica and increase the number of hair roots per plant, but has little effect on shoot ratio.2) Nitrogen deposition increases the biomass of each part of C. aromatic, including leaf, stem, main rhizome, lateral rhizome, root tuber and hair root.However,nitrogen deposition has no effects on biomass allocation.3)Nitrogen deposition has little effects on the content and ratio of chlorophyll a, chlorophyll b and carotenoids.But it promotes the growth of leaf area thereby increasing the photosynthetic area; In addition, nitrogen deposition can increase the net photosynthetic rate and stomatal conductance, and can increase photosynthetic capacity.4)Nitrogen deposition has no effects on the content and ratio of Nitrogen,Phosphorus and Potassium in each part of C. aromatic,and nitrogen deposition doesn't result in nutrient imbalances at high concentration.5)Nitrogen deposition increases the content of soluble sugar and reduces the content of soluble protein and free amino acids; According to the synthetically evaluation of resistant indexes,included CAT,POD and free proline, nitrogen deposition has little effect on stress resistance.6)Nitrogen deposition increases the yield of rhizoma curcumae,rhizome wenyujin concisum and radix curcumae,but has no effects on the content of volatile oil and curcumin.7)At the high concentration,nitrogen deposition appeares promoting effects on the growth of C. aromatic rather than negative effects.2 Effects of nitrogen deposition on physical and chemical properties of soil1)Nitrogen deposition reduces pH value of rhizosphere soil and non-rhizosphere soil.2)Nitrogen deposition has no effects on total nitrogen content of non-rhizosphere soil,but increases the nitrogen content of rhizosphere soil. It has no effect on available phosphorus content of rhizosphere soil and non-rhizosphere soil. Nitrogen deposition also has no effects on available potassium content of non-rhizosphere soil,but increases the potassium content of rhizosphere soil.3)The responses of four kinds of soil enzyme to nitrogen deposition are different.Among them,nitrogen deposition has the most significant promoting effect on invertase activities. It also increases catalase activity of soil at the low concentration and presents opposing effects at the high concentration. Besides, it has little effects on phosphatase activity and urease activity of soil.4)The response of non-rhizosphere soil to nitrogen deposition is different from rhizosphere soil.3 Effects of nitrogen deposition on field weeds1)There are 18 species of weeds, belonging to 10 families and 16 genera.Dicotyledon plants have 14 species, 13 genera of 8 families and monocotyledon plants have 4 species, 3 genera of 2 families.Among them, Compositae is the most with 6 species and 5 genera.2)Nitrogen deposition also increases weed species at the low concentration and presents opposing effects at the high concentration.Total weed density is basically in accordance with weed species. The response of weed density to nitrogen deposition depends on weed species.3)Nitrogen deposition increases the biomass of weeds at the low concentration and presents opposing effects at the high concentration. Besides,weed biomass has a close relation with above-ground biomass of C. aromatica.4) Nitrogen deposition changes the relative dominance of weeds and affects the structure and composition of weed community.The response of relative dominance of weeds to nitrogen deposition depends on weed species.5) Species richness indexes,Shannon-Weiner diversity index, Pielou evenness index and Sinpson dominance index have the same result basically, which shows that nitrogen deposition increases the diversity of weeds under low N treatment level, while presents opposing effects under high N treatment level.4 Effects of nitrogen deposition on soil macrofauna1)485 soil animals belonging to 19 groups were obtained. The dominant groups are Oligochaeta and Hymenoptera, the number of common groups is 8, and the number of rare groups is 9. Both group number and individual number reach maximum in the 0-5cm Layer.2)Nitrogen deposition changes surface gathering of the individual number of soil macrofauna, so the highest number occurred in the deeper soil layer under high N treatment level. Nitrogen deposition reduces the individual number, which shows CK>T100>T150 in the 0-5cm Layer.3) Nitrogen deposition has little effect on the vertical distribution of group number,but it reduces the group mumber,which also shows CK>T100>T150 in the 0-5cm Layer.4) Shannon-Weiner diversity index, Pielou evenness index and Sinpson dominance index have the same result basically, T100>T50>CK>T150, which shows that nitrogen deposition increases the diversity of soil animals under low N treatment level, while presents opposing effects under high N treatment level. 5)The diversity of soil macrofauna and the fresh weight of weeds show a good positive correlation (r=0.74),furthermore, the fresh weight of weeds and C. aromatica show a good negative correlation (r= -0.79).It shows that the effects of nitrogen deposition on soil macrofauna may be a more complex process affected by weeds and crops.In a word, nitrogen deposition has an important influence on the agroecosystem of C. aromatica.Different components of ecosystem related closely in the ecosystem have different responses to nitrogen deposition,which also closely linked and mutually influence.