The response of rice plant to perennial application of vermicompost alone and plus with different chemical fertilizers

Organic fertilizers such as vermicompost (VC) are an undeniable source of required nutrients of plants. This field experiment performed as split plot arrangement based a randomized complete block design with three replications in 2008. The main factors (vermicompost treatments) added to soil at six levels including 20 and 40 ton.ha^-1, 20 and 40 ton.ha^-1 plus (1/2) chemical fertilizer, chemical fertilizer (consists of 100 kg.ha^-1 urea, 150 kg.ha^-1 triple superphosphate and 100 kg.ha^-1 potassium sulphate based on soil testing analysis) and control. Also, sub plots considered VC application periods (1, 2 and 3 years). Results showed that using VC and also fertilization year's factor significantly affected studied traits of rice. So, 40 ton.ha^-1 VC plus 50% chemical fertilizer determined as the best fertilizer level, because the maximum content of biomass (12.43 ton.ha^-1), tiller number, height, total number of grains in panicle (124.3), harvest index (41.41%) and yield (681.1 g.m²) and also the lowest percent of unfilled grain in panicle (15.52%) recorded in this treatment. Meanwhile, 40 ton vermicompost per hectare treatment had the highest panicle fertility percentage (94.08%). Increasing application periods regularly enhanced the content of studied traits. In addition, the maximum positive and significant correlation coefficient (r= +0.91^**) existed between paddy yield and harvest index.