Study On The Effects Of The Nitrogen Fertilizer On The Lettuce's Yield And Quality And The Soil's Environment Quality

Regard lettuce as the experiment material, adopting the pot experiment and pot culture experiment, the experiment were carried out with different nitrogen fertilizer types and different types of fertilizer together with the nitrogen fertilizer regulator, the different nitrogen fertilizer dosage experiment, the different nitrogen fertilizer application mode, The reaserch studied the effects on the lettuce's growth development, yield, nourishment and safe quality, and on the nitrate nitrogen,PH and conductivity of the soil.Results showed:1)Different types of nitrogen fertilizer affect the lettuce's growth differently. Nitrate nitrogen accelerates growth, ammonium nitrogen inhibits growth, the depression effect of ammonia chloride is obvious. The nitrate nitrogen makes the vegetable nitrate quickly rising, the ammonium nitrogen especially the ammonia chloride nitrate decrease the nitrate content. Compare synthetically, It should appropriately apply the nitrate nitrogen or nitric－ ammonium fertilizer in the prophase, It should apply the ammonium nitrogen. fertilizer in the anaphase to decrease the nitrate content of the vegetable 2)The excessive dosage in nitrogen fertilizer inhibit the growth, lowering the vegetable quality, quickly increasing the nitrate and the nitrite content.At the same time, the soil PH descends, conductivity and the nitrate nitrogen rises, deteriorating the soil environment. As the lettuce, nitrogen fertilizer application dosage is proper under 30 g/ m2.3)Early application of the nitrogen fertilizer can promote the growth, which is beneficial to the quality, also avoid the nitrate and nitrite accumulation , excessive top dressing in the anaphase is disadvantage to growth and quality of the vegetable, also threatens vegetable and soil safety, the traditional excessive top dressing in the anaphase should change.4)The nitrogen fertilizer together with the nitrification inhibitor and unease inhibitor can prolong the effect of the nitrogen fertilizer, accelerate growth, increasing vegetable quality, also can lower the bad effect on the soil environment of the nitrogen fertilizer, but its effect is limited.5)The vegetable more safe after applying fertilizer two weeks, the top dressing is not proper to apply in the anaphase.6)As the lettuce nitrate content ,petiole>blade, exited>endive , the nitrite is contrary, but it is not significant.