RESUMO
Climatic conditions significantly affect the maize productivity. Among abiotic factors, nitrogen (N) fertilizer and temperature are the two important factors which dominantly affect the maize (Zea mays L.) production during the early crop growth stages. Two experiments were conducted to determine the impact of N fertilizer and temperature on the maize growth and yield. In the first experiment, the maize hybrids were screened for their sensitivity to temperature variations. The screening was based on the growth performance of the hybrids under three temperatures (T 1 = ambient open-air temperature, T 2 = 1°C higher than the ambient temperature, and T 3 = 1°C lower than the ambient temperature) range. The results showed that an increase in temperature was resulted less 50% emergence and mean emergence (4.1 and 6.3 days, respectively), while emergence energy and full emergence were higher (25.4 and 75.2%, respectively) under the higher temperature exposure. The results showed that Syngenta 7720 and Muqabla S 25W87 were temperature tolerant and sensitive maize hybrids, respectively. The second experiment was carried out to study the response of the two selected maize hybrids (Syngenta 7720 and Muqabla S 25W87) to four N fertilizer applications. The results revealed that the maximum N use efficiency (19.5 kg kg-1) was achieved in maize hybrids with low N application (75 kg N ha-1 equivalent to 1.13 g N plant-1). However, the maximum maize grain yield (86.4 g plant-1), dry weight (203 g plant-1), and grain protein content (15.0%) were observed in maize hybrids that were grown with the application of 300 kg N ha-1 (equivalent to 4.52 g N plant-1). Therefore, it is recommended that the application of 300 kg N ha-1 to temperature tolerant maize hybrid may be considered best agricultural management practices for obtaining optimum maize grain yield under present changing climate.
RESUMO
The use of efficient rates of nitrogen (N) fertilizer application is important with regard to increasing crop productivity and maintaining environmental sustainability. Rice-oilseed rape rotations are a mainstay of the economy and food security of China. Therefore, a field experiment was carried out during 2011-2013 in Honghu to identify the most appropriate N application rates for enhancing crop productivity and N use efficiency for rice (Oryza sativa L.)-oilseed rape (Brassica napus L.) rotations. Six N fertilizer treatments (RO1, RO2, RO3, RO4, RO5, and RO6) were laid out in a randomized complete block design with three replicates. ROx represented the N fertilizer application rates (kg ha-1) for rice and oilseed rape, respectively. Grain yields from plots receiving N fertilizer were significantly increased by 59-71% (rice) and 109-160% (oilseed rape) during the total rotation (2011-2013), as compared to RO1 (control; no application). Furthermore, a similar trend was observed for N accumulation, ranging from 88 to 125% and 134 to 200% in aerial parts of rice and oilseed rape, respectively. Nitrogen use efficiency (NUE) was significantly higher (38.5%) under RO2 and lower (34.2%) under RO6 while apparent N balance (ANB) was positively lowest under R05 (183.4 kg ha-1) followed by R02 (234.2 kg ha-1) and highest under R06 (344.5 kg ha-1) during the total rotation. The results of grain yield, NUE, and ANB indicated that the R02 rate of N application was superior. This information should help to develop a cost-effective and environment-friendly N management strategy for rice-oilseed rape rotation systems of central China.
RESUMO
A 2-year experiment was conducted to ascertain the effects of exogenously applied plant growth regulators (PGR) on rice growth and yield attributes under high day (HDT) and high night temperature (HNT). Two rice cultivars (IR-64 and Huanghuazhan) were subjected to temperature treatments in controlled growth chambers and four different combinations of ascorbic acid (Vc), alpha-tocopherol (Ve), brassinosteroids (Br), methyl jasmonates (MeJA), and triazoles (Tr) were applied. High temperature severely affected rice morphology, and also reduced leaf area, above-, and below-ground biomass, photosynthesis, and water use efficiency, while increased the leaf water potential of both rice cultivars. Grain yield and its related attributes except number of panicles, were reduced under high temperature. The HDT posed more negative effects on rice physiological attributes, while HNT was more detrimental for grain formation and yield. The Huanghuazhan performed better than IR-64 under high temperature stress with better growth and higher grain yield. Exogenous application of PGRs was helpful in alleviating the adverse effects of high temperature. Among PGR combinations, the Vc+Ve+MejA+Br was the most effective treatment for both cultivars under high temperature stress. The highest grain production by Vc+Ve+MejA+Br treated plants was due to enhanced photosynthesis, spikelet fertility and grain filling, which compensated the adversities of high temperature stress. Taken together, these results will be of worth for further understanding the adaptation and survival mechanisms of rice to high temperature and will assist in developing heat-resistant rice germplasm in future.
