抄録
Experiments were conducted in 1997 and 1999 to determine how long-term soil fertilization influences the performance of maize crop under water deficit on alluvial soil (sandy loam) at the Kyoto University Farm, Japan. The field had been applied large amounts of chemical fertilizer and/or farmyard manure since 1988 as four treatments, i.e., no fertilizer (NF), chemical fertilizer (CF), farmyard manure (MF) and chemical fertilizer + manure (CM) each with two replications. Water stress was imposed naturally in 1997 from 54 to 81 days after sowing (DAS). In 1999, water stress was imposed in one of the two replicate blocks artificially during 22-65 DAS by controlling irrigation under a rain shelter and another replicate block was well watered. Leaf area index and biomass in CM and MF were maintained higher than in CF and NF in both years under both water-stressed and well-watered conditions. With the progress of water stress, the major water depletion zone in the soil tended to shift deeper to a greater extent in MF and CM than in NF and CF. The total amount of water depleted from 100cm-depth soil during the stress periods was larger in MF and CM than in NF and CF by 20 to 80 percent. Water-use efficiency (biomass production per total water depletion) was similar in OF, MF and CM with an average of 3.9 g kg>-1< and it was lower in NF (1.8 g kg>-1<) Leaf conductance and photosynthetic rate during the stress period were higher in MF than in CF. The results indicated that water extraction during the stress period was greater in the plots manured for a tong time, which resulted in well-maintained physiological activity and growth.
