Effect of water stress at different development stages on vegetative and reproductive growth of corn Recep C ¸akir * Water Management Department, Ataturk Rural Services Research Institute, P.O. Box 55, 39100 Kirklareli, Turkey Received 9 May 2003; received in revised form 13 January 2004; accepted 13 January 2004 Abstract A field study was carried out from 1995 to 1997 in order to determine the effect of irrigation and water stress imposed at different development stages on vegetative growth, grain yield and other yield components of corn (Zea mays L.). The field trials were conducted on a silty loam Entisol soil, with Pioneer 3377 corn hybrid. A randomised complete block design with three replications was used. Four known growth stages of the plant were considered and a total of 16 (including rain fed) irrigation treatments were applied. The effect of irrigation or water stress at any stage of development on plant height, leaf area index, grain yield per hectare, as well number of ears per plant, grain yield per cob and 1000 kernels weight, were evaluated. Results of this 3- year study show that all vegetative and yield parameters were significantly affected by water shortage in the soil profile due to omitted irrigation during the sensitive tasselling and cob formation stages. Water stress occurring during vegetative and tasselling stages reduced plant height, as well as leaf area development. Short-duration water deficits during the rapid vegetative growth period caused 28–32% loss of final dry matter weight. Highest yields were observed in the fully irrigated control (VTCM) and the treatment which allowed water stress during the vegetative growth stage (TCM). Even a single irrigation omission during one of the sensitive growth stages, caused up to 40% grain yield losses during dry years such as 1996. Much greater losses of 66–93% could be expected as a result of prolonged water stress during tasselling and ear formation stages. Seasonal irrigation water amounts required for non-stressed production varied by year from 390 to 575 mm. Yield response factor (k y ) values (unitless parameter) relating yield loss to water deficits) obtained for the first, second and third experimental years were determined to be 1.22, 1.36 and 0.81, respectively. # 2004 Elsevier B.V. All rights reserved. Keywords: Irrigation; Corn; Water stress; Growth; LAI; Grain yield; Yield response factor (k y ) 1. Introduction Corn grain yields up to 15 t ha 1 can be obtained under irrigated conditions in the Thrace region in north- west Turkey, while yields of 5 t ha 1 are considered good in rain fed agriculture. Recently there has been interest in optimising irrigation application due to water scarcity in the region. The cost of irrigation pumping and inadequate irrigation scheme capacity as well as limited water sources are among the reasons that force many farmers to reduce irrigation applications. The fact that water stress effects on growth and yield are species- and variety-dependent is well known. More- over, sensitivity to drought varies by development stage (Doorenbos and Kassam, 1979). Moisture stress Field Crops Research 89 (2004) 1–16 * Corresponding author. Tel.: þ90-288-214-48-85 and þ90-288-214-29-44x109; fax: þ90-288-214-2026. E-mail addresses: crec56b@yahoo.com, rcakir@khgm.gov.tr (R. C ¸akir). 0378-4290/$ – see front matter # 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.fcr.2004.01.005