The green grass was a disguise. What lay beneath, however, was a surface that Karnataka’s spinners exploited ruthlessly, bowling Assam out for 135 before the visitors raced to 180 for two on the opening day of their Ranji Trophy Elite Group B encounter at the ACA Stadium here on Monday.

Spinners Ritesh Bhatkal (five for 35) and Shikhar Shetty (five for 53) combined for all 10 wickets before Karnataka ended day one 45 runs in the green.

Captain Shreyas Gopal’s decision to introduce spin early paid dividends after Assam won the toss and elected to bat.

Karnataka, noticing the green tinge on the surface, started with pace and an aggressive field set-up, positioning fielders at short-leg and deep-fine.

That strategy did not go according to plan, but the green layer’s bluff was exposed soon after. Underneath it lay a dry, grippy surface that Ritesh and Shikhar made full use of once they were introduced into the attack from the seventh over.

Captain Denish Das (26, 72b) and Sibsankar Roy (37, 66b), Assam’s best batters this season, were the only ones to put up a fight.

Denish and Sibsankar stitched together a 63-run partnership for the fourth wicket, with the latter being the aggressor. Just when the association began to flourish, Sibsankar fell to Ritesh.

Ritesh completed his five-for in the first over of the second session by sending back Denish before Shikhar also reached the landmark — his third five-wicket haul this season — by wiping out Assam’s tail in no time.

In reply, Karnataka openers Rohan Patil (89, 87b, 13x4, 1x6) and Mayank (57 batting, 95b, 7x4) got off the blocks strongly with a 129-run partnership.

Rohan, however, missed his maiden First Class century due to a stunning reflex catch by Sibsankar at first slip off Amlanjyoti Das’ bowling.

The scores: Assam — 1st innings: Nibir Deka c Karun b Ritesh 12, Pradyun Saikia b Ritesh 13, Sumit Ghadigaonkar lbw b Shikhar 1, Denish Das b Ritesh 26, Sibsankar Roy b Ritesh 37, Sarupam Purkayastha c Manvanth b Shikhar 13, Amlanjyoti Das c Karun b Shikhar 12, Roshan Alam lbw b Ritesh 7, Mukhtar Hussain c & b Shikhar 0, Mohit Thakur (not out) 0, Hridip Deka b Shikhar 0; Extras (b-12, lb-1): 13; Total (in 48.1 overs): 135.

Fall of wickets: 1-19, 2-20, 3-30, 4-93, 5-98, 6-121, 7-130, 8-130, 9-130.

Karnataka bowling: Kaverappa 3-1-9-0,Manvanth 6-3-15-0, Ritesh 18-4-35-5, Shikhar 17.1-4-53-5, Shreyas 4-0-10-0.

Karnataka — 1st innings: Rohan Patil c Sibsankar b Amlanjyoti 89, Mayank Agarwal (batting) 57, K.L. Shrijith lbw b Amlanjyoti 19, K.V. Aneesh (batting) 7; Extras (lb-5, nb-3): 8; Total (for two wkts. in 36 overs): 180.

Fall of wickets: 1-129, 2-157.