Effects of Tillage Systems, Planting Method and Nitrogen Amounts on the Yield of Rapeseed (Brassica napus L.) and Some Properties of Soil in Paddy Field Conditions

The aim of this study was to investigate the effects of tillage, planting method and the levels of nitrogen fertilizer on the grain yield and some properties of soil in planting Rapeseed (Brassica napus L.) as a second crop after rice.

A split factorial experiment in complete randomized block design was conducted with three replications at research fields of Rice Research Institute of Iran in Rasht during two cropping seasons of 2016-2018. In the experiment, three tillage methods including the conventional tillage (moldboard plow at a depth of about 25-30 cm + double-disc), minimum tillage (once using tractor-mounted rotavator at a depth of about 10-15 cm) and no-tillage were considered as the main plots. In addition, two planting methods of direct planting and transplanting as well as the four amounts of nitrogen fertilizer of 0, 100, 200 and 300 kg.ha-1 urea source were considered as factorial in sub plots.

Results showed that the minimum tillage at 200 kg ha-1 of nitrogen had the highest grain yield with the average of 4144.3 kg.ha-1. The system of no-tillage had the maximum soil bulk density (1.58 g.cm-3), cone index (3.74 MPa), soil moisture (72.13%), minimum root length (20.65 cm) and root weight (61.43 g.m-2). The treatment of without nitrogen consumption showed the minimum values of soil nitrogen, organic carbon as well as root length and weight.

Based on the results, the combination of minimum tillage by using 200 kg.ha-1 of nitrogen in both planting methods could be recommended for rapeseed production in Guilan region due to the high grain yield.