The effect of irrigation period and N-Fertilizer on yield of rapeseed (Brassica napus L.)

In regard to importance of rape seed in production of vegetable oil, it is necessary to pay attention factors of production including water period and N-fertilizer. Rapeseed needs to much N-fertilizer،In the other hands water restriction is preventative factor in rape seed plant. Therefore determination of irrigation period with N-formulation that cause increasing rape seed yield is needed.

The trial was conducted as a split plot factorial experiment in randomized complete blocks design with 4 replications and tow crop years at Broujerd Agricultural Research station. In this design, Irrigation period was I1=50 mm, I2=75mm and I3=100mm collective evaporation from pan A as main plot and three rate of urea via N1=0.7R=112 kg.ha-1, N2=R=160 kg.ha-1 and N3=0.3R= 208 kg.ha-1 (R: Was determined base on recommendation Department of Nutrition, Institute of Soil and Water Research) was subplot. N fertilizers were consumed in three stage Contains planting, Stems and flowering. In this research was used from Regent X Cobra cultivar.

The results obtained indicated that among irrigation treatments, the most of seed yield Related to I1 (50 mm collective evaporation from pan A) and I2 (75 mm collective evaporation from pan A) treatments with amount of seed yield 3146 and 3164 kg.ha-1 respectively which was significantly different to I3 (100 mm collective evaporation from pan A) with seed yield of 2684 kg.ha-1 Also maximum number of seeds per pod and pod per plant were obtained I1 treatment. There was a positive correlation among seed yield, plant height, number of seeds per pod and pod per plant. Maximum water use efficiency was obtained by I3 treatment(100 mm collective evaporation from pan A) with amount of 0.394 kg.m-3 which was significantly different with other treatments at a probable level of 1%. The effects amount of nitrogen on water use efficincy, seed yield, the number of seed per pod, the number of pod per plant,plant height and 1000 of seed weight was significantly. Among interaction effect of irrigation and N rates, the most of seed yield was obtained by I2N1 treatment with 3498 kg.ha-1 and the lowest seed yield was obtained by I3N1 with 2401 kg.ha-1.

According to the results, irrigation from the beginning of April to the maturity, with irrigation interval of 75 mm, collective evaporation from pan A, is suitable and nitrogen fertilizer consumption with 0.7 amount of recommended by the plant nutrition research department of the soil and water research institute by splitting in three stages during planting, stemming and flowering stage in similar region of Borujerd, is recommended. Therefore, in order to increase the yield of rapeseed under Borujerd weather conditions, the use of nitrogen fertilizer is 0.7 times recommended by the Institute for Soil and water research and irrigation with irrigation intervals based on 75 mm cumulative is recommended as a result of that an effective step towards optimal use of agricultural inputs and ultimately achieving sustainable agriculture.