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Accueil du site → Doctorat → Allemagne → 2011 → Resource utilization and sustainability of conservation-based rice-wheat cropping systems in Central Asia

Rheinischen Friedrich-Wilhelms-Universität Bonn (2011)

Resource utilization and sustainability of conservation-based rice-wheat cropping systems in Central Asia

Devkota, Krishna Prasad

Titre : Resource utilization and sustainability of conservation-based rice-wheat cropping systems in Central Asia

Auteur : Devkota, Krishna Prasad

Université de soutenance : Rheinischen Friedrich-Wilhelms-Universität Bonn

Grade : Doktor der Agrarwissenschaften (Dr. agr.) 2011

Résumé partiel
Excessive and inefficient water use, intensive soil tillage and decreasing soil fertility have caused land degradation and desertification, which are threatening the sustainability of rice-wheat systems in the irrigated lowlands of Central Asia. Water-saving and conservation agriculture (CA) practices such as alternate wet and dry irrigation (WAD), direct seeding on raised beds, zero tillage flat lands, and residue retention can help counterbalancing these threats. A randomized complete block design experiment with four replications was conducted from 2008-2010 in rice-wheat rotation systems in Khorezm region, Uzbekistan. Objectives were to (1) investigate the growth and yield formation of rice, (2) examine mineral-nitrogen (N) dynamics in a rice-wheat system, and (3) evaluate the sustainability of a rice-wheat system under water-saving irrigation and CA practices. Next, the rice growth model ORYZA2000 was parameterized and evaluated to assess the impact of increased temperature on phenology and grain yield of rice at various emergence dates under IPCC (2007) projected A1F1 and B1 climate change scenarios. The rice variety used was a puddle rice variety subjected to dryland conditions. The field experiment centered on six WAD rice treatments involving dry-direct seeded rice (DSR) under raised bed planting (BP) and zero tillage (ZT) planting on flat land combined with three levels of residue retention, i.e., residue harvested (RH), 50% residue retention (R50), and 100% residue retention (R100). These were compared with wet-DSR grown under conventional tillage (CT) with continuous flood irrigation (CT-FI) and with intermittent irrigation (CT-II). The WAD and CT-II treatments were irrigated only when the soil water potential in the top 20 cm soil reached around -20 kPa. CT-FI was irrigated as practiced by the farmers in the region. Wheat was surface seeded into the standing rice field in all treatments. To assess the impact of climate change with ORYZA2000, field experiments with six seeding dates and three varieties were conducted in 2008-2009.

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