Abstract
Increment of rice production to feed the growing population under increasing water scarcity is of great concern for recent days. Moreover, the water is a very limiting input for crop production and its efficiency is relatively low. In addition, nitrogen (N) management in rice cultivation is crucial to achieve higher productivity in irrigated agricultural systems. Physiological attributes and yield performance of high yielding rice cultivars need to be assessed by minimizing water and nitrogen loss. Therefore the study was undertaken to find out appropriate cultivars and formulate associated water and nitrogen management practices. Five experiments on cultivar screening and agronomic management practices were carried out at the Bangladesh Agricultural University, Mymensingh, Bangladesh during 2015 to 2017. Ten high yielding boro (dry season irrigated) rice cultivars were tested in pot culture in the net house of Agronomy department during 2015. The cultivars BRRI dhan28, BRRI dhan29, BRRI dhan60, Binadhan-8 and Binadhan-10 were selected based on water management and yield. BRRI dhan29, BRRI dhan59, Binadhan-8 and Binadhan-10 were selected on the basis of nitrogen management and yield. These selected cultivars were evaluated considering water and nitrogen management practices in field condition during 2016 and 2017. In respect of water management, Binadhan-10 had the highest value of leaf area index (LAI), number of effective tillers hill⁻¹, and number of grains panicle⁻¹. Growth, TDM, yield, and agronomic efficiency (AE) were increased with water application up to 8 days after disappearance (DAD) of 4 cm ponded water after which these factors declined with increasing water stress at 10-DAD and alternate wetting and drying (AWD). The water productivity was the highest (0.080 t ha⁻¹ cm⁻¹) in 8- DAD treatment, obviously due to highest yield and because of optimum use of water. Considering nitrogen management, Binadhan-8 had the highest yield among the cultivars because of the highest total dry matter (TDM), number of effective tillers hill⁻¹, and number of grains panicle⁻¹. Growth, TDM, yield, and agronomic efficiency (AE) were highest with 105 kg N ha⁻¹ from prilled urea (PU) with 3 t ha⁻¹ poultry manure application. The highest N uptake in grain and straw (120.1 kg ha⁻¹ and 96.14 kg ha⁻¹, respectively) was found in rice cultivar Binadhan-8. In addition, significant relationships between N concentration and growth dynamics, TDM, N content, N uptake, and yield were observed. It indicated that cultivars with the capacity to uptake more N produced more yield and N application along with poultry manure enhanced growth, yield and AE. In combined experiment, Binadhan-8 had highest value of LAI, number of effective tillers hill⁻¹ and number of grains panicle⁻¹. Growth and yield were increased and water productivity was the highest (0.057 t ha⁻¹ cm⁻¹) with water application at 8- DAD. Application of 105 kg N ha⁻¹ from PU with 3 t ha⁻¹ Poultry manure produced the highest growth and yield. Interaction between water and nitrogen management, cultivars and water management was significant for several parameters. Besides, interaction among cultivars, water and nitrogen management was significant for grain yield. The combined application of water at 8-DAD and N sources in the form of PU with poultry manure showed good performances in terms of growth and yield of Binadhan-8. Therefore, the present study was useful for the selection of the most efficient cultivar, which could be strongly recommended to rice growers to improve crop yield and reduce the use of water and nitrogen.