EFFECT OF NITROGEN LEVELS ON GROWTH PERFORMANCE AND BIOMASS OF MAIZE FORAGE GROWN IN NORTHERN PROVINCES

Abstract

Biomass maize cultivation represents a viable strategy for mitigating the shortage of green forage for livestock. A field experiment was conducted to determine appropriate nitrogen (N) fertilizer levels for biomass maize production using the maize variety NK7328 during the Autumn - Winter season 2024 in Son La and Cao Bang province and the Winter season 2024 in Vinh Phuc and Nghe An province. Results indicated that the highest observed biomass yield of the maize variety NK7328 was 57.06 t/ha at the treatment of 170 kg N. Moreover, a quadratic regression model predicted the maximum yield at approximately 180 kg N, suggesting that the practical optimum nitrogen levels should be used in the range from 170 to 180 kg N. The analysis results also showed that, across all four provinces, the average nitrate content in maize stems increased progressively with higher nitrogen application levels, ranging from 404.93 mg/kg at 140 kg N to 453.88 mg/kg at 180 kg N. Compared to previous studies, all nitrogen application levels in this experiment remained within the safe thresholds for use as green forage for ruminants, even when used as the sole feed source.