NITROGEN METABOLISM OF SOYBEAN AT SATURATED SOIL CULTURE AND WATERING CULTIVATION OF FARMER’S SYSTEM IN CONDITIONS OF TIDAL LAND

This research aimed to study the effect of the water-saturated cultivation system of Tidal land on nitrogen metabolism in soybean. Treatment was growing plants on benches, at the different water levels of trenches-which were 15 cm, 20 cm, and 25 cm from the soil surface- arranged in a randomized block design with three replications. The results showed that the height of standing water in the trench affected the soil water, leaf proline, and N content. The water level of 15 cm had a higher soil water potential (-0.48 MPa), the proline content of 1.52 mol/g fresh leaf weight, and the N content of leaves was 2.6% than those of 20 cm and 25 cm. The lowest N content and leaf chlorophyll content were obtained at a height of water level of 25 cm, namely 1.79% leaf fresh weight and 1.74% leaf fresh weight, respectively, but, higher proline content was found at 2.47µmol/g fresh leaf weight. Thus, both the water level of the bench of 15 cm and 20 cm had better nitrogen metabolism. Plants grown at the benches of 25 cm can still withstand low soil water content, proven by their highest leaf proline content. The increase in proline value in soybeans under stress conditions was caused by de novo synthesis, not due to protein degradation. The mechanism of nitrogen metabolism in soybean (C3) under mild stress conditions is postulated to be the same as nitrogen metabolism in corn (C4)