The Effects Of Different Substrates And Fertilizer On The Growth Of Lettuce And The Microorganism And Enzyme In Soilless Culture

The experiment was carried out with the two kinds of substrates (S₁, S₂) and four types of fertilizer (F₁, F₂, F₃, F₅). The S₁ was organic and inorganic mixed substrate (sunflower's straw: vermiculite=3:1). The S₂ was inorganic mixed substrate (vermiculite: perlite: zeolite =2:1:2). The fertilizer types were organic (F₁),inorganic (F₂),organic plus inorganic (F₃) and nutrition solution (F₅). The treatment of no fertilizer (F₄) was taken as control (CK₁) to compare the difference of microorganism and enzyme activity among the treatments in the substrates. The F₅ was taken as control (CK₂) to compare the difference of growth of lettuce (variety: Caesar) among the treatments. The physical and chemical properties of substrates, the effects of different kinds of substrate and fertilizer types on the growth,physiological characteristics,yield,nutrient absorption of lettuce and the microorganism and activity of enzyme in the substrates were analyzed. The results were showed as follows: (1)The physical and chemical characteristics of substrates and fertilizer were tested. The results indicated that the two substrates were suitable to lettuce cultivation. Organic fertilizer could improve the physical and chemical properties and granular structure of substrates and enhance the substrate's capacity of holding water,fertilizer and air, moreover, it also contained rich mass and micro element. The efficiency of inorganic fertilizer was fast and concentrated. So organic and inorganic fertilizer supplemented each other and supplied enough nutrition for growth of lettuce. (2)The effects of different substrates and fertilizer on the growth,physiological characteristics and yield of lettuce were significantly different. Among different fertilizer, the growth of lettuce cultured with both organic and inorganic fertilizer was the best,the second was the treatment of only organic or inorganic fertilizer, and the last was the nutrition solution. Compared S₁ with S₂, the fresh weight of root,diameter of shoot,root activity and leaf chlorophyll content of lettuce planted in organic and inorganic mixed substrates were higher than those in inorganic mixed substrates, moreover, the number of leaves and fresh weight of leaf were significantly increased in organic and inorganic mixed substrates. (3)It was shown by the results of nutrient absorption of lettuce that the amount of K absorption was the most and the amount of P absorption was the least during the cultivation, which accorded with characteristics of nutrient absorption in lettuce. Under the different fertilizer types, the amount of N,P,K absorption of lettuce fertilized with organic plus inorganic fertilizer was most and the amount of N,P,K absorption of lettuce fertilized with nutrition solution was least. Compare S1 with S2, the amount of N,P,K absorption of lettuce planted with organic and inorganic mixed substrates was higher than inorganic mixed substrates. (4)The results of effects of different substrates and fertilizer on microorganism and activity of enzyme in the substrates showed that the influence of only organic fertilizer and organicï¹¢inorganic fertilizer was the biggest, which improved rhizosphere microenvironment and enhanced microorganism quantity and activity of enzyme. The second was only inorganic fertilizer. The last was nutrition solution that decreased the quantities of fungi and actinomyces and the activities of some enzymes such as urease and proteinase. The number of bacteria,fungi,ammonifier,cellulose-decomposing bacteria and the activity of urease,cellulosase,proteinase and phosphatase in organic and inorganic mixed substrates were significantly higher than that in inorganic mixed substrates. Microorganism's massive multiplication in the substrates may accelerate the decomposition of organic matter,fix nutrient temporarily and enhance the validity of nutrient. The enzyme participated the biochemistry process in the substrates, which was connected with the release and storage of nutritive elements,the humus formation in the substrates,the structure and physical conditions of the substrates. Therefore microorganism and enzyme were the useful targets to reflect the activity of substrates and the transformation of nutrition.