IMBIBITION RESPONSE OF WINTER-WHEAT TO WATER-FILLED PORE-SPACE

Reduced temperature and increased bulk density associated with conserv ation tillage systems cause lower seed germination, seedling emergence , and early growth rates resulting in reduced plant stands. Prediction of the influence of soil condition on seed imbibition through simple soil measurements would help make agronomic decisions such as planting date and/or density. Our objectives were to evaluate the influence of soil water-filled pore space on winter wheat (Triticum aestivum L.) s eed imbibition and to assess the possibility of describing the relatio nship through simple mathematical models. We measured the rate of wate r uptake by heat-killed wheat seeds at three levels of water-filled po re space (WFPS: 0.35, 0.60, and 0.85) and temperature (T: 278, 283, an d 288 K) and two levels of bulk density (Pb: 1.25 and 1.40 Mg m(-3)) i n a Sharpsburg silty clay loam topsoil. The model proposed in 1972 by Blacklow to estimate seed water content (theta(s)) after imbibing wate r for time t, theta(s(t)) = (m + ot) - (m - theta(s(0))) e(-qt), was f itted to seed water content as a function of time and initial seed wat er content, theta(s(0))., This equation adequately described the proce ss of water absorption (for 18 treatment combinations, R(2) greater th an or equal to 0.963). The model parameter 0 was related (R(2) = 0.88) to WFPS and rho(b), and q was related (R(2) = 0.78) to T and WFPS. Th e third parameter, m, was significantly but weakly related (P<0.01, r( 2) = 0.26) to initial seed weight. We showed that easily measured sail properties and simple mathematical models can be used to predict whea t seed imbibition under a variety of soil conditions.