عنوان مقاله
اثرات مدیریت سفره آب بر شوری خاک و عملکرد یونجه در اقلیم نیمه خشک
فهرست مطالب
چکیده
مقدمه
مواد و روش ها
نتایج و بحث
بخشی از مقاله
ساخت لایسی متر
مطالعه در سال 2005 و 2006 (مارس تا ژولای) در مزرعه پژوهشی مرکز تحقیقات آب و خاک دانشگاه تهران در شهر کرج انجام شد.این مطالعه با 12 لایسی متر نصب شده در وسط یک زمین 0.8 هکتاری صورت گرفت. برای قرار دادن لایسی متر در یک عمق مشخص، خاک تا جایی حفر شد که راس لایسی متر ها تا سطح زمین رسید. خاک حفر شده سپس به جای اول برگردانده شد. لایسی مترهای با ارتفاع 1.5 متر از لوله های پلی اتیلن با قطر 70 سانتی متر با انتهای بسته با یک صفحه دایره ای ایجاد شدند. لوله های با قطر 0.05 متر در بالاتر از انتهای هر لایسی متر جهت نفوذ آب به لایسی متر نصب گردیدند.
کلمات کلیدی:
EVects of water table management on soil salinity and alfalfa yield in a semi-arid climate Hamideh Noory · Abdol-Majid Liaghat · Mohamad Reza Chaichi · Masoud Parsinejad Received: 12 November 2008 / Accepted: 24 March 2009 © Springer-Verlag 2009 Abstract A lysimeter experiment was conducted to investigate the eVect of water table management (WTM) on distribution of soil salinity and annual alfalfa (Medicago scutellata) yield. Subirrigations with three levels of water table namely, 0.5 (WT0.5), 0.7 (WT0.7), and 1.0 m (WT1.0) and a free drainage (FD) conventional irrigation treatment were selected for this study. All treatments were arranged in a complete randomized block design with three replicates. The results of this study indicated that the average soil electrical conductivity of the saturated extract (ECe) in the root zone gradually increased and exceeded the designated crop threshold value (4 dS/m) after the Wrst forage harvest in subirrigated lysimeters. A higher salt accumulation was observed at the WT0.5 treatment. The average dry matter yield of annual alfalfa in WT0.5 and WT0.7 treatments was found to be 52 and 73% higher compared with the control treatment, respectively. Introduction Water table management has shown to increase crop production and drainage water quality in humid regions (Workman et al. 1990; Kalita et al. 1992; Fisher et al. 1999; Jia et al. 2006). Conventional subsurface drainage has long been proved to have substantial impact on quality and quantity of various crop productions, whereas many recent studies have shown that many crops respond more favorably to the practice of controlled drainage and subirrigation systems, instead (Soppe et al. 2001; Fausey and Baker 2003; Ayars et al. 2003). In controlled drainage system, the drain outlet is raised to a speciWed level in order to retain a portion of percolating water in the soil proWle to supplement crop water requirements. In subirrigation system, however, water is introduced through subsurface drainage pipes to maintain the water table just below the root zone to fulWll crop water requirements (Fausey and Baker 2003). Some of the advantages attributed to WTM are: reduction in drainage water and losses of chemicals, reduction in environmental pollution, and provision of a better soilwater environment for crop growth (Skaggs and Evans 1996; Mejia et al. 2000). Skaggs et al. (1999) compared the performance of controlled drainage, subirrigation and free drainage systems for management of drainage water in a 4- ha Weld study. Nitrate concentration of drainage water was reduced by 63% in the controlled drainage system and the total nitrate losses were reduced by 50% compared with the free drainage system. Tomato and corn yields in the subirrigation system were 44 and 64% more than those in the free drainage system, respectively. Ahonen (1991) reported a 10% increase in potato yield in the subirrigation as compared to the free drainage system. Mejia et al. (1998) also reported 75-84% reduction of nitrate losses and 42% increase in corn yield through water table management.
