Decrease of nitrate and restoration of mineral balance in forage field soil and corn plant in dairy farms

Excess nitrogen corresponding to about 2-3 times the amount required for fo rage plant growth had been applied continuously for many years in dairy far ms at Shisui machi, Kumamoto Prefecture in Kyushu because of the limited ar ea of crop fields. Field experiments with reduced application of animal was tes (RAAW) which contained only half the amount of requirements for corn pl ant growth were conducted to decrease nitrate nitrogen (NN) accumulation an d restore the mineral balance in corn plants and crop field soil in 6 dairy farms. (1)The NN concentration in the corn stem decreased to less than 5 g /kg (dry matter basis) and no whole plant shoots with a NN concentration ab ove 2 g/kg were observed after the reduction of animal waste application fo r 1 year. (2) The content of exchangeable potassium (EK) in the dairy farm soil decreased from 60 to 27 mg/100g after RAAW for 2 years. (3) Average dr y yield of corn plants in the 4th year was 16% lower in the case of RAAW th an in the case of excess utilization of animal composts, but the difference was not significant. The concentration of K was lower in RAAW, which resul ted in the decrease of the K/(Ca+Mg) equivalent ratio from 1.78 to 1.15 in the corn plants. These data suggest that RAAW can improve the feed quality by reducing the NN content and restoring the mineral balance in plant.