White bud and small bunched leaves at the top of my maize, is this zinc deficiency (khaira)?

Yes, that white bud or white tip look, with small bunched top leaves and shortened spacing between leaves, is the classic picture of zinc deficiency in maize. Zinc shortage gives broad whitish or pale yellow bands on either side of the midrib on younger leaves while the midrib and leaf edge can stay green, plus stunting and a rosette-like crowding of the top leaves because the stem stops elongating. Zinc deficiency is very common on high pH soils, sandy soils, leached soils and where heavy phosphorus has been applied, since phosphorus and zinc compete. Please confirm with your Soil Health Card or soil test, because the white striping can be confused with herbicide injury or genetic striping. The standard correction is soil application of zinc sulphate, with foliar zinc sulphate sprays for a quick rescue on a standing crop. Soil doses are commonly in the range of roughly 8 to 10 kg zinc sulphate (heptahydrate) per acre applied at sowing for deficient soils, and a foliar spray is often around a 0.5 percent zinc sulphate solution, sometimes with a little lime added to prevent leaf burn, sprayed a couple of times. Adjust the exact dose to your soil test and local KVK recommendation, and do not over-apply, because zinc can build up and turn toxic.