The decline in rice yields as a result of excessive chemical fertilizer (CF) inputs is a matter of great concern in rice-growing regions of Asia. In two-year’s field experiments, the nitrogen, phosphorus, and potassium (NPK) status, growth characteristics and yield of rice were examined by application of poultry manure (PM), cow manure (CM) and compost (CP). Organic fertilizers were applied as EMN (estimated mineralizable N) based on their total N content. Six treatments were assigned in a randomized complete block design: (1) no-N fertilizer (N0); (2) 50% CF (CF50), (3) 100% CF (CF100); 50% CF + 50% EMN from (4) PM or (5) CM or (6) CP. Compared with CF100, the CF50PM50 (total N ≥ 4%) accumulated higher N, P and K content in leaf, sheath, panicle and seeds, resulting in greater growth and yield. The CF50PM50 increased yield by 8.69% and 9.70%, dry matter by 4.76% and 5.27% over CF100 in both years. The continuous application of CF50CM50 (total N < 4%) and CF50CP50 (total N < 4%) treatments led to similar NPK contents but higher yields than those of CF100 treatment in 2018. In conclusion, the organic fertilizer (total N ≥ 4%) with the EMN method enhances higher N availability in each year. Continuous application of organic fertilizer (total N < 4%) over two years effectively increased N availability in the second year. The 50% organic fertilizer (total N ≥ 4%) and 50% CF led to increased NPK availability and rice yields over the 100% CF treatment, reducing CF usage and leading for sustainable agriculture.

When rice is grown under moderate salinity (6 dS m −1), yields are reduced by up to 50%. The development of salt-tolerant varieties is a key strategy for increasing yields. We conducted an experiment using a hydroponic system with ion components similar to seawater to determine useful parameters for assessing salt tolerance. Two-week-old seedlings were grown for 7 days on Yoshida hydroponic solution. The treatment group then additionally received an artificial seawater solution (electrical conductivity, 12 dS m −1). After a 2-week period of salt stress, standard evaluation scores (SES) of visual salt injuries were assessed. The K, Na, Mg, and Ca contents were then determined in the roots, sheaths, and leaves of each plant. Following the SES results, we divided the 37 genotypes into four groups: salt-tolerant groups (STGs), moderately salt-tolerant groups, salt-sensitive groups (HSSGs), and highly salt-sensitive groups (HSSGs). In the control, STGs had the highest sheath K content (30.1 mg g −1 dried weight [DW]), whereas HSSGs had the lowest (21.4 mg g −1 DW). Sheath K was also highly and negatively correlated with SES. This suggests that sheath K may be useful for identifying salt-tolerant varieties under non-saline conditions. Plant growth was significantly affected under salt stress, but STGs had the smallest decrease in sheath DW. SES was significantly correlated with sheath and leaf Na, sheath K and Mg, and sheath and leaf Na/K and Na/Mg ratios. The results suggested that sheath K, Na/K, and Na/Mg may be useful indicators for genetic analyses of salt-tolerant varieties under salt-stress conditions. The salt-tolerant cultivars, KCR20, KCR124, and KCR136, are possible candidates for such studies because they had high sheath K content (31.19, 31.21, 29.44 mg g −1 DW, respectively) under non-saline conditions and low SES (3.3, 3.6, 3.9, respectively), and low sheath Na/K (0.64, 0.52, 0.92, respectively) and Na/Mg ratios (2.96, 2.27, 3.03, respectively) under salt-stress conditions.

No abstract

A field experiment was conducted to investigate the effects of pretransplant basal (surface application, BSF, and incorporation methods, BIC) and split applications of nitrogen (N) on the growth and yield parameters of rice. Using 120 kg N ha −1 except (N0, control), different percentages of N rate were applied at basal, tillering, and panicle initiation in five N split treatments. Growth parameters and dry matter were greater in BIC than BSF until panicle initiation stages. Among N split applications, N2 (25:50:25) using low basal surface N was optimized for maximum dry matter and yield. With large incorporated basal N, N1 (50:25:25) obtained greater dry matter and yield but did not differ from N4 (50:50:0). With omitted N at tillering, N5 (50:0:50) did not increase rice yield or dry matter by either method. This study highlighted that N split-application patterns affect the growth and yield parameters of Manawthukha rice.

Weed infestation has an adverse impact on the yield of vegetable corn. This study, therefore, aimed to investigate the effects of plant density and hand weeding on controlling weeds and yield of vegetable corn. The experiments were conducted in the field condition in a randomized complete block design with three replications. The planting densities were 79,365 plants ha-1 (D1); 92,593 plants ha-1 (D2); 111,111 plants ha-1 (D3); and 138,889 plants ha-1 (D4). The hand weeding treatments were no weeding (NW), hand weeding once at 3-4 leaf stage of vegetable corn (HW1), and hand weeding twice at 3-4 leaf and 8-9 leaf stages of vegetable corn (HW2). The results showed that the highest planting density combined with hand weeding was generally effective in controlling weeds. Furthermore, the increase in planting density combined with hand weeding significantly improved the physiological traits, which consequently increased the cob yield. The yield was optimum at D3 combined with hand weeding once. Thus, the results suggested that the optimum yield of vegetable corn could be obtained at a planting density of 111,111 plants ha-1 combined with hand weeding once at 3-4 leaf stage, an increase of the cob yield by 2.01 tons ha-1.