Studies On Several Techniques For Nutrient And Water Management In Protected Agriculture

Media planting and fertigation under protected condition are new trends in morden agriculture. With the pot experiments, the growth of watermelon seedlings on different media was studied, and nitrogen use efficiency of tomato was also determined by 15N-tracer technique. With the field experiment, the effects of K and Mg fertilization on the yield and quality of strawberry fruits were elucidated. The results were summarized as follows:1. In the pot experiment, 40% cottonseed and 60% rotten straw mixture was the best of the seven media for watermelon seedling growth, as the biomass of seedlings (FW) was 25.52 g/pot, and significantly higher than those of other treatments. This result implyes that rotten straw can be used as one of fundamental media materials.2. The results of the pot experiment with fertigation indicated that the biomass of tomato plants grown on 50% pig feces and 50% turf mixed media (27.5 g DW/pot) was significantly higher than that of 100% turf media (14.3 g DW/pot), and the nitrogen use efficiency of two media were 41% and 53%, respectively. The mixed media with 50% pig feces and 50% turf is valuable in practical application based on the better growth of tomato seedlings, though its nitrogen use efficiency is lower than that of turf media.3. It was obtained that the biomass of tomato plants grown on 40% pig feces and 60% coconut hull mixed media was 14.1 g DW/pot, significantly higher than that of other media. Nitrogen use efficiency in 40% pig feces and 60% coconut hull mixedmedia was 42%, significantly higher than that of other media as well. These results indicate that pig feces used as a part of media (40%) can increase both tomato growth and nitrogen use efficiency.4. The results of the experiment with soil culture indicated that appropriate reduction of N fertilizer and increase of P, K fertilizers (Treatment 4) significantly increased the yield of strawberry fruits with the comparison of Treatment 1 (solid complex fertilizer) and so did the increase of P, K fertilizers with more frequent fertigation (Treatment 3). Reduction of N, P, K nutrients applied with more frequent fertigation (Treatment 5) could remain the yield of strawberry fruits, which might be reasonable for the control of salinity of soils under greenhouse condition. It was also observed that the quality of strawberry fruits was mainly affected with the harvesting period, and strawberry fruits harvested in the middle harvesting stage had better quality as which were be with high soluble sugar contents and low titratable acidity. At the beginning of the harvesting stage (in Nov, 2001), fertigation with soluble fertilizers (Treatment 2-5) could improve the quality of strawberry fruits by increasing soluble sugar content and the ratio of S/A(sugar/acid).5. Potassium fertilization significantly increased the fruit yields of watermelon. The watermelon fruit yields of K fertilization treatments (K2O 225 kg/ha and 450 kg/ha) were 31139 kg/ha and 32889 kg/ha, higher than that of the control (25556 kg/ha). At high level of K fertilization (K2O 450 kg/ha), magnesium application significantly increased the fruit yields of watermelon with the comparison of treatment NPK2Mg to treatment NPK2.Sugar contents of watermelon fruits significantly increased comparing treatment NPK2Mg with treatment NP (11.58% vs 9.56%), and so did S/A ratio (ratio of sugar content to titratable acidity) as there were no significant differences on titratable acidity among the all treatments. High level K fertilization with magnesium addition obviously increased fruit Vc content comparing with treatment NP, but not significantly. Theseresults imply that integrated fertilization of K and Mg can improve quality ofwatermwlon fruits.