Response of Rice Harvest Index to Different Water and Nitrogen Management Modes in the Black Soil Region of Northeast China

Understanding the methods leading to rice yield increase is vital for sustainable agricultural development. Improving the harvest index (HI) is an important way to increase rice yield. To explore the effects of different water and nitrogen management modes on the rice HI in the black soil region of Northeast China, a field experiment was conducted in 2019 (Y1) and 2020 (Y2). Two irrigation methods, conventional flooding irrigation (FI) and controlled irrigation (CI), were established in the experiment, and four nitrogen application levels (0 kg/ha, 85 kg/ha, 110 kg/ha, and 135 kg/ha) were set during the entire growth period, named N0, N1, N2, and N3. The dry matter weight and the rice yield at the maturity stage were determined, and the HI was then calculated. The results showed that different irrigation modes and nitrogen application levels had significant effects on the rice HI. Under different irrigation modes with the same nitrogen application level during the two years, the comparison regular of HI was consistent. In Y1 and Y2, the HI of FN0 was 3.36% and 5.02% higher than that of CN0 (p < 0.05), and the HI of CN1 was 0.31% and 2.43% higher than that of FN1 (p > 0.05). The HI under CI was significantly higher than that under FI under N2 and N3 (p < 0.05), the HI of CN2 was 4.21% and 4.97% higher than that of FN2, and the HI of FN3 was 13.12% and 20.34% higher than that of CN3. In addition, during the two-year experiment, the HI first increased and then decreased with an increase in the nitrogen application rate under FI and CI. Under the FI treatments, the HI of N1 was the highest, and that of N2 was the highest under the CI treatments. A variance analysis showed that the irrigation pattern and nitrogen application level had significant interactions on the rice HI (p < 0.01), and the appropriate water and N management mode could increase rice the HI by 26.89%. The experimental results showed that the HI of the 110 kg/ha nitrogen application rate under CI was the highest, reaching 0.574 and 0.572, respectively, in two years. This study provides a data reference and theoretical support for realizing water savings, nitrogen reduction, and sustainable agricultural development in the black soil region of Northeast China.

Impact of vermicompost based nitrogen management and plant spacing on the performance of short duration transplant Aus rice (cv. Parija)

An investigation was carried out at the Agronomy Field Laboratory, Bangladesh Agricultural University to inspect the effect of vermicompost based nitrogen management and plant spacing on the yield performance of short duration transplant Aus rice (cv. Parija). The study comprised three spacing viz. 20 cm × 20 cm, 20 cm × 15 cm and 20 cm × 10 cm, and five nitrogen management viz. no nitrogen, 75 kg N ha-1, 55 kg N ha-1 + vermicompost @1.25 t ha-1, 35 kg N ha-1 + vermicompost @2.5 t ha-1 and vermicompost @5 t ha-1. The experiment was laid out in a Randomized Complete Block Design with three replications. At harvest, both the spacing of 20 cm × 20 cm and 20 cm × 15 cm produced the tallest plants, the highest number of total tillers hill-1 and effective tillers hill-1. The highest grain yield (3.59 t ha-1) was recorded in 20 cm × 15 cm spacing which was at par with the grain yield (3.52 t ha-1) in 20 cm × 10 cm spacing. The 20 cm × 10 cm spacing also produced the highest straw yield (4.88 t ha-1) and biological yield (8.40 t ha-1). The lowest grain, straw and biological yields were recorded at the wider spacing of 20 cm × 20 cm. In contrast, the highest grain yield (3.79 t ha-1), straw yield (4.99 t ha-1) and biological yield (8.79 t ha-1) were found in 75 kg N ha-1 which was as good as the yields of 55 kg N ha-1 N+ vermicompost @1.25 t ha-1. The highest number of total tillers hill-1 (14.11) and effective tillers hill-1 (12.67) were found in the interaction effect of 20 cm × 20 cm spacing with 75 kg N ha-1. The interaction between 20 cm × 15 cm and 55 kg N ha-1 N+ vermicompost @1.25 t ha-1 gave the highest grain yield (4.58 t ha-1), straw yield (5.71 t ha-1) and biological yield (10.29 t ha-1). The lowest grain yield (2.03 t ha-1), straw yield (3.49 t ha-1) and biological yield (5.52 t ha-1) were found in the interaction between 20 cm × 20 cm and no nitrogen. Therefore, usage of 20 cm × 15 cm spacing fertilized with 55 kg N ha-1 + vermicompost @1.25 t ha-1 appeared as the promising practice of transplant Aus rice cv. (Parija) cultivation.