Timing of N fertilization on N2 fixation, N recovery and soil profile nitrate dynamics on sorghum/pigeonpea intercrops on Alfisols on the semi-arid tropics uri icon

abstract

  • In a field trial in the 1993 rainy season at Patancheru, Andhra Pradesh, India, sorghum cv. CSH 5 and Cajanus cajan cv. ICP 1-6 were grown as sole crops or intercropped and were given fertilizer N at sowing or 40 days after sowing (delayed application). N was applied only to the sorghum rows in the intercropping treatment. Delayed N application increased sorghum dry matter and grain yields, but not those of C. cajan. Delaying N application to sorghum significantly increased 15N recovery in shoots from 15 to 32% in the sole crop, and from 10 to 32% in the intercrop. Similarly, there was a significant increase in N recovery from 43 to 59% in sole crop and from 28 to 71% in intercropped sorghum. Fertilizer N recovery by sole crop C. cajan (14%) was higher than for the intercrop (2-4%). C. cajan fixed between 120 and 170 kg ha-1 of atmospheric N throughout the cropping season. Although there was a marked difference in nitrate-N (NO3-N)concentrations between basal and delayed treatments at sowing, no difference was observed in NO3-N concentrations in soil solution between the treatments at 40 days after sowing. The rate of N depletion from the soil solution was 2-3 times faster than N accumulation by plants, suggesting that an appreciable amount of NO3-N would disappear from soil solution in the top soil without being utilized by crops during the initial growth stage

publication date

  • 1997
  • 1997