Chemical and physical properties of Pak Chong Soils under cropping with Conventional and No-tillage systems and different rates of Nitrogen fertilizer in the fourteenth year.

 

Thammanoon Kaewkhongkha

Kasetsart University  Bangkok  10900

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            Changes in nitrate-nitrogen (NO^-₃-N) content in Pak Chong Soils (Very fine clay, kaolinitic, acid Paleustults) cropped to corn (Zea mays L.) under conventional tillage (CT) and no-tillage (NT) systems in different rates of N fertilization including control plot (0-0-0, 0-10-10, 10-10-10, 20-10-10, 30-10-10) were investigated in 1997 at the National Corn and Sorghum Research Centre, Nakhon Ratchasima province.  Corn has been grown under two tillage systems annually since 1984.  In the 14^th year of cropping (1997), the amount of NO^-₃-N accumulation in the 0–90 cm soil depth, average over N rates, tended to be grater under the CT when compared with the NT system throughout the growing season.  The NO^-₃-N content was increased in subsoil (30–90 cm) more than in the topsoil layer (0–30 cm).  The amount of NO^-₃-N in the top layer tended to be greater under the NT than the CT at the initial state growth of corn.  The average NO^-₃-N content of the two tillage systems was as high as 27.9 kg NO^-₃-N /rai at 4 week after planting or 2 weeks after fertilizer application, was decreased with time, reached the lowest value of 5.86 kg NO^-₃-N /rai at the grain filling stage and slightly increased at harvesting time.  Higher rate of N fertilizer (30 kg N/rai) resulted in higher soil NO^-₃-N accumulation when compared with lower rates.  Unfortunately, the higher the soil NO^-₃-N accumulation was also the grater the loss of nitrogen from the soil resulting in no difference of soil total N among the various rates of N supply.  It was also found that the above ground corn dry matter was greater with the CT than the NT system at the initial stage growth of corn, but at the flowering stage and thereafter there was no difference between the two tillage systems.  The latter was also true for corn grain yield.  However, the NT system resulted in greater soil moisture content, organic matter and total N in the topsoil than those of the CT.  Moreover, soil pH of the two tillage systems was significantly decreased as N supply increased.

 

 

 

No-tillage