ارزيابي شاخص هاي رشد در آفتابگردان ، رقم ركورد، تحت شرايط ديم

Evaluation of growth indices in rainfed sunflower

To evaluate the seed production and growth indices of sunflower (CV. Record) in dryfarming system an experiment was conducted at Gonbad Agricultural Research Station in 1995. The experimental design was a split plot in completely randomized blocks with four replication. Sowing dates were allocated as main plots (three levels: dl= Marchl6 th, d2= March3 1 th, d3= April 16 th). The row space and the spaces between plants on the rows were factorials allocated as subplots (R1=60cm, R2=70 cm) and two levels of spaces between plants on the rows (W 1= 20cm and W2=30cm). Growth indices including CGR(Crop growth rate), RGR(Relative growth rate), LAI(Leaf area index) and NAR(Net assimilation rate). Yield increased with late in planting date. Highest yield was obtained in d3 in sowing pattern RI W 1, d2 sowing pattern R2W 1 and in dl sowing pattern Rl W 1. Sowing pattern of R2W 1 at dl and d2 and sowing pattern of Rl W l cm at d3 had the highest crop growth rate. In all sowing dates the RGR index of R2W 1 cm sowing pattern was higher than other patterns, and thereby the higher value of crop growth rate of R2W 1 cm sowing pattern is justifiable. In dl and d2 the RI W 1 cm sowing pattern and in d3 the R2W I cm sowing pattern had a higher LAI. The LAI of all sowing patterns in d 1 was significantly higher due to longer growing period. The highest LAI value of all sowing pattern at dl and d2 was obtained at flowering(870 and 1030 GDD, respectively) while at d3 it was obtained at seed setting period(at 1350 GDD).The relatively lower reduction of NAR of sowing patterns in d3 comparing to d 1 and d2 .