Journal of Research on Crop Ecophysiology
Volume:10 Issue: 1, Winter 2015

Lowland rice (Oryza sativa L.) in South Asia is under stress, as nitrogen removals by crops are higher than their replenishment through fertilizers. Limited information is available on optimizing nitrogen dose in lowland rice to turn out higher yield. The present investigation aimed to optimize nitrogen fertilization and it’s response to the growth and yield of lowland rice. We evaluated two modern rice varieties (BRRI dhan28 and BRRI dhan29) under six nitrogen rates ranging from 0 to 250 kg ha-1 during the dry season. Positive response of nitrogen fertilization was observed in tiller and dry matter production from the early growing stage in both varieties. Tillering increased progressively with the advancement of growth stage and reached at the peak within 60 days after transplanting (DAT) in all cases. BRRI dhan28 and BRRI dhan29 achieved the highest dry matter at 75 and 90 DAT with 250 kg N ha-1. The relationship between N application and N uptake by plants became quite evident at 30 DAT and beyond. N uptake started to increase from 45 DAT and showed a peak at 75 DAT in both the varieties. Nitrogen application significantly increased the grain yield of both varieties. The highest yield of 5.15 and 6.34 Mg ha-1 was obtained with 150 kg N ha-1 in BRRI dhan28 and BRRI dhan29, respectively. However, the nitrogen dose was optimized at 156 and 158 kg ha-1 for BRRI dhan28 and BRRI dhan29, respectively.

The present study was aimed to investigate the planting dates effects on yield associated traits and also determining stability of the result of factor analysis and stepwise regression analysis in different planting dates of rapeseed genotypes at Biekol Agriculture Research Station during 2011-12 cropping season. Result of split plot analysis exhibited significant genotypes effects for phenological traits, yield components and seed yield indicated significant differences of the genotypes for these traits. All the traits except 1000-seed weight were significant affected by planting dates. Significant positive correlation was detected between days to flowering and days to maturity in four planting dates. The correlation between seeds per pod with 1000-seed weight and seed yield were significant in all planting dates. Seed yield and biological yield had also significant and stable correlation. Based on stepwise regression analysis seeds per pod had important role in first and second planting dates, but in third and fourth planting dates, pods per plant was more important than other yield components for seed yield prediction model.

This study was carried out in farm of Dehkhoda institute (2013-2014). The study was done as randomized complete blocks design with five potassium sulfate amounts (0, 50, 100, 150 and 200 kg/ha) and four replications. According to results, potassium affected the number of stalk numbers, yield, and the amount of obtainable sugar (p < 0.01) and purity (P < 0.05). The highest stalk numbers (186351), yield (111.62 ton/ha), obtainable sugar (10.86 %), and purity (89.9%) were obtained in 200 kg/ha potassium. Results showed that the amount of potassium in the mentioned region is not sufficient and adding potassium as potassium sulfate will increase the qualitative-quantitative yield of sugarcane.

Salinity stress is among the major barriers to plant production in many parts of the world, especially in arid and semi-arid areas. Jasmonates are one of the newest plant growth regulators that reduce the damages caused by environmental stresses. In this study, the effects of salinity and methyl jasmonate on some morphological traits of chamomile including root and shoot lengths, fresh weights and dry weights were evaluated. Seeds were planted in green house in pots as a completely randomized design with three pots as replications for each treatment. Plants were treated with 100 and 200 mM concentrations of salt at the four-leaf phase for six days alternately. Methyl jasmonate was sprayed on plants at concentrations of 0.01-0.1 µm/l along with salinity treatments which was continued for 6 hours. Salinity and methyl jasmonate reduced stem length. Salinity reduced dry and fresh weights in proportion to control group. But methyl jasmonate improved the effects of salinity. Growth study of root and shoot in seedlings showed salinity effects and reduction in weights. Increased dry and fresh weights of treated plants in proportion to control group showed the protective effect of methyl jasmonate.

In order to assess the environmental impact of agricultural activity, the long-term sustainability should be considered. In order to achieve solutions to reduce energy consumption and carbon emissions in the production of rainfed sunflower, this assessment was conducted in the North East of Iran. Four production methods, i.e. conventional tillage (CT), tow reduced tillages (RT1and RT2) and direct seeding (NT) were evaluated. The highest energy consumption (12.3 GJ.ha-1) and carbon emissions (248 kg C-eq ha-1 and 155 kg C-eq t-1) were related to the conventional method. The least energy input (9.12 GJ ha-1) and carbon emission (183.3 kg C-eq ha-1 and 118.6 kg C-eq t-1), were related to NT method. The greatest amount of sustainability index (Is) was related to NT method, followed by RT2 (1.96), RT1 (1.79) and CT (1.53). In farm operations, fuel and nitrogen fertilizer were the key factors relating to energy use and carbon emission. In comparison of production methods, the conservation tillage was significantly more efficient. In conservation tillage, input energy and fuel consumption per hectare were 30% and 90% lower than conventional method, respectively, but there was no reduction in yield and energy output. Based on the lower power consumption and greater energy efficiency, conservation tillage methods (in particular, reduced tillage and no-tillage) was recommended to  replace the conventional tillage.