Agronomic responses and nitrogen use efficiency of local and introduced corn (Zea mays L.) genotypes to varying levels and sources of nitrogen in two corn growing areas in Timor Leste

The experiment was conducted from May to September 2009 (dry season) in two corn growing areas in Timor Leste (East Timor) with varying climatic and soil characteristics to evaluate the agronomic response, productivity and nitrogen (N) efficiency of five corn genotypes (Local variety, Sele, Suwan 5, IPB var 4 and USM var 10) under eight N fertilizer treatments: (control (without fertilizer); P and K without N; 30 kg N/ha (100% organic); 30 kg N/ha (50% organic + 50% inorganic); 30 kg N/ha (100% organic); 60 kg N/ha (100% organic); 60 kg N/ha (50% organic + 50% inorganic); and 60 kg N/ha (100% inorganic)). Evaluations were based on agronomic and physiological parameters, yield and yield components, and N use efficiency. The growth and yield of corn varieties were better in Lospalos than Baucau, this was due to pronounced water limitation during 2009 dry season in Baucau. Application of N fertilizer at 30-60 kg N/ha did not improve the growth and yield of corn plants due to water limitation in both sites. The N recovery efficiency of corn plants were not also affected by N fertilizer application, although Sele and Suwan 5 had relatively higher N recovery efficiency. On the other hand, the internal efficiency of N increased with increasing fertilizer N application (0-60 kg N/ha) in 100% organic fertilizer application. This was also observed on Local variety and Sele in Baucau (severe water limitation), and on Suwan 5 in Lospalos (unstressed during early vegetative stage). Generally, Suwan S and the Local variety had better overall performance in Lospalos and in Baucau, respectively. Further evaluation is needed using varying sources of N fertilizer at 0-30 kg N/ha for possible improvement of yield and NUE [nitrogen use efficiency] of these genotypes during wet season where water is not limiting in East Timor.