Cotton and wheat are two most important crops of Pakistan. Food and Agriculture Organization of the United Nations reported that boron deficiency occurred widely in Pakistan, especially under cotton-wheat cropping system. High soil pH and CaCO 3 content are the major factors of low boron (B) availability in alkaline calcareous soils; therefore, this study was conducted to assess the leftover effects of B on wheat in these soils. For this purpose ten B treatments (0, 0.25, 0.50, 0.75, 1, 1.25,

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... 50, 1.75, 2 and 3 kg B ha-1) as boric acid were applied to cotton. After the harvesting of cotton, wheat was sown in the same plots as a test crop without B application, but all other nutrients were applied at recommended rates. Soil analysis showed that B concentration gradually increased from 0.17 mg kg-1 (at control) to 0.36 mg kg-1 (at 3 kg B ha-1) after the cotton harvest in B application plots. The average highest soil B concentration of 0.24 mg kg-1 was obtained after first year cotton harvest followed by second year (0.21 mg B kg-1) whilst the lowest soil B concentration of 0.19 mg kg-1 was obtained after the third season of cotton. This study revealed that residual B applied to previous cotton crop has a significant effect on wheat crop in terms of yield and growth. No toxic effect of residual B was observed in wheat. The highest grain yields of 4.70 t ha-1 and 4.58 t ha-1 were obtained from 1.50 kg B ha-1 treated plots during first and second years, respectively while the minimum was obtained from control. There was a highly significant linear relationship (P< 0.05) between residual B levels and plant B content of the first wheat crop (R 2 = 0.96 **) and second wheat crop (R 2 = 0.93 **) seasons.