Abstract
Tomatoes were cultivated in a vinyl greenhouse using Red-Yellow soil with low fertility. Thereafter, the effects of succesive applications of large amounts (50t/10a, 50t plot) of farmyard manure (FYM) on the yield of tomato and population of soil microorganisms were analyzed compared with practical applications (5t/10a, 5t plot) of FYM. Several crops were grown twice without fertilizer application between the third and fourth croppings of tomato. Yields and soil microorganism population were also evaluated. (1) The yields of tomato in the 50t plot and 5t plot were not significantly different until the third cropping. On the fourth cropping, the yield of the 50t plot was lower than that of the 5t plot due to salt accumulation. But the yields during the fifth to sixth croppings at which FYM was not applied were higher in the 50t plot than in the 5t plot. (2) Changes in the soil microbial population were remarkable and there was little difference between the amounts of FYM applied. However, the B/F (Bacterial/Fungal numbers determined by the dilution plate method) ratio and the numbers of ammonium-oxidizing bacteria tended to be higher in the 50t plot than in the 5t plot. (3) In the 50t plot, the successive changes in the population of ammonium-oxidizing bacteria were similar to the changes of the nitrate nitrogen contents. (4) During three croppings, nitrogen fertility in the 5t plot did not increase, whereas that in the 50t plot increased remarkably and remained at high levels after two croppings of tomato grown without FYM. (5) The yields of several crops in the first cultivation period between the third and fourth croppings of tomato were higher in the 50t plot. (6) In the soils where several crops were grown, the numbers of fungi and bacteria were higher in the 5t plot and 50t plot, respectively. B/F ratio was higher in the 50t plot and in the soil where sorghum and corn were grown.
