The affix yat comes in the sense of 'a place of growing, when it is a field' after the words 1. yava 2. yavaka and 3. ṣaṣṭika,
This debars खञ् ॥ Thus यवानां भवनं क्षेत्रं = य꣡व्यम्, यवक्य॑म्, षष्टिक्य॑म् ॥ See 6.1.213 for accent.,
यव-यवक-षष्टिकाद् यत्
Adhyāya 5 · Pāda 2 · Rule 3