Dry matter yield and nitrogen uptake of maize at various nitrogen - and two soil moisture levels

Abstract

The pot experiment was carried out in a growth-house. The dry matter weight and nitrogen uptake was examined at suboptimum and optimum water suppiy. Beside control and PK-treated plants there were 6 nitrogen rates. The lowest N rate was 1.2 g and the highest 7.2 g. The increment was 1.2 g. All N treatments contained the same amounts of P and K. At suboptimum water supply the plants reached their highest dry matter yield at N2.4PK-treatment, being not significantly different from N1.2PK. Higher rates of N application decreased the total dry matter and the lowest value, 57% of the maximum yield, was obtained at the highest N-rate. No generative plant parts developed in the control and PK-treatment. As a result of increasing N-rates the most pronounced dry matter decline was observed in the grain yield. At optimum water supply the highest dry matter yield was obtained also in the N2,4PK-treatment, but now being almost twice as high as in the water-stressed treatment. While in the water-stressed plants the grain yield peak was observed in the N1.2PK-treatment, at optimum water supply the plants gave the highest grain yield in the N2.4PK-treatment. The grain yield ratio of water-stressed vs. unstressed plants decreased with increasing N-rate and reached the lowest value of 35% at the highest N application rate. At suboptimum water supply the grain contained more nitrogen at a higher N-dose (N2.4PK) than we could see at the grain dry matter yield (N1.2PK). The optimum water supply modified the nitrogen content of plant parts (roots, grain,husks) since the maximum value moved toward the higher N-doses. With the exception of PK-treated plants in each treatment the nitrogen concentration was higher at water-stressed plants. At both soil moisture levels the highest nitrogen concentration was observed at the highest nitrogen rate. In all treatments the nitrogen yield was higher at optimum water supply. At the lowest nitrogen rate (N1.2PK) there was only a small difference in nitrogen content of plants between the two levels of water supply. At higher nitrogen rates the differences were much greater. There was a weaker correlation between the transpired water and the total nitrogen content of the whole plant at water-stressed plants (r=0.57***) than at those grown at optimum water supply (r=0.68***).