waving heads of grain
Refers to the visual effect of grain ears swaying in the wind like waves. Often used in poetic or descriptive contexts.
Waves of grain heads are rippling in the autumn rice field.
風が吹くたびに黄金色の穂波が広がる。
Whenever the wind blows, golden waves of grain spread out.
Compound of 穂 (ho, 'ear of grain') and 波 (nami, 'wave'). The reading ほなみ is a straightforward combination.