Examination of photosynthetic nitrogen use efficiency of field- grown sweet corn (Zea mays L var merit) under water and nitrogen stress

The physiological response to drought stress in sweet corn (Zea mays L var merit) is not well understood. Water and nitrogen utilization properties of leaves can play key roles in plant drought tolerance. During the grain-filling period, increasing photosynthesis per unit plant N, namely photosynthetic N-use efficiency (PNUE) is a potential way to increase N-utilization efficiency (NUtE). The objective of this study was to determine whether the PNUE within the canopy is optimized as a method of maximizing canopy productivity under low N conditions and/or wa- ter stress. Sweet corn plants were grown in the field in two consecutive years with three N levels (0, 175, and 225 kg N ha−1) and two water regimes (100 and 60 percent field capacity). Throughout the grain-filling period significant interactions of irrigation regime x nitrogen fertilization on specific leaf N (SLN), net photosynthetic rate (P ), PNUE (calculated as P /SLN), stomatal conductance (gs), transpiration rate (E) and green leaf area (GLA) were measured every 10 d after silking (DAS). Significant differences in SLN, P , gs, E, and PNUE occurred in leaves. Ear FM with- out N (N0) (13.69 and 15.56 Mg ha−1 across 2 yr) was 37% and 45% and 34% and 41% less than the average of N125 and N225 across both years, but physiological NUtE increased by 21% without N. Correspondingly, PNUE at high levels of N was similar to that of the full irrigation, with both of them having smaller PNUE than the lower of N. In conclusion, improved whole-plant NUtE under water stress and with N0 may both contribute to the high degree of physiological acclimation of sweet corn to drought and the overall increase in PNUE in the leaves

Split nitrogen sources effects on nitrogen use efficiency, yield and seed quality of safflower (Carthamus tinctorius L.)

The effects of nitrogen (N) on crop yields have historically been assessed with field trials, but selection and use of the best sources and optimal timing N applications have a significant role in realizing the maximum potential of oilseeds quality and quantity. This study was conducted to determine the combine effects of N sources (ammonium nitrate (AN), ammonium sulfate (AS), sulfur coated urea (SCU), and urea (U)) and split N fertilization ((1/4,3/4,0), (1/3,1/3,1/3), (1/2,1/2,0), and (1/3,2/3,0)) on safflower (Carthamus tinctorius L.) some growth characters, yield and seed quality, and N use efficiency based on a split plot design with three replications at the experimental research station, Shiraz University in 2015 and 2016. The highest safflower dry matter (5140.93 kg ha-1), seed yield (3303.52 kg ha-1) and protein yield (694.95 kg ha-1) were achieved with the application of AN fertilizer in a split pattern of 1/2,1/2,0 (applying half of the N at sowing time and the rest at stem elongation), while the highest oil yield (753.09 kg ha-1) was observed by U fertilizer and similar split pattern. Applying AN fertilizer and split patterns of 1/3,2/3,0 (applying one third of the N at sowing and two thirds of the N at stem elongation) and 1/4,3/4,0 (applying one quarter of the N at sowing and three quarters at stem elongation) maximized safflower N uptake efficiency (NUpE) (0.78 kg kg-1). However, the highest N utilization efficiency (NUtE) (43.70 kg kg-1) was obtained when AN fertilizer in a split pattern of 1/2,1/2,0 was applied. On the contrary, applying AS and SCU fertilizers was less effective on safflower performance by all split patterns. It is concluded that applying AN fertilizer in a split pattern of 1/3,2/3,0 and or U fertilizer in a split pattern of 1/2,1/2,0 not only enhanced safflower growth, yield and seed quality improved, but also increased the N use efficiency of safflower

Effect of Salinity Stress on Growth, Yield and Some Physiological Traits of Forage Sorghum Cultivars

In order to evaluate the effect of salinity stress on growth, yield, and some physiological traits of forage sorghum cultivars, an experiment was conducted as split-plot based on a randomized complete block design with four replications at experimental farm of College of Agriculture, Shiraz University at 2014 growing season. Treatments were three levels of saline irrigation water (0.4 as control, 7 and 14 dS/m) and three sorghum cultivars (Pegah, White speedfeed and Red speedfeed) as main plots and subplots, respectively. Results showed that salinity stress decreased plant height and leaf area. Pegah cultivar showed the highest forage dry weight in all salinity treatments. Activity of antioxidant enzymes including superoxide dismutase, peroxidase and catalase significantly increased with increasing salinity levels in Pegah and Red speedfeed cultivars. In salt-stressed Pegah these enzymes activity increased 2.1, 4.5, and 2.8 times, respectively in comparison to control. With increasing salinity levels, shoot sodium/potassium ratio of White speedfeed, Red speedfeed, and Pegah cultivars increased  10.7, 6.8, and 1.7 times, respectively whereas root sodium/potassium ratio of the cultivars increased 9.6, 8.1, and 4.7 times, respectively. It seems that the lower absorption of sodium was the major mechanism of salinity tolerance in Pegah and can be an important criterion to evaluate sorghum salinity toleranc

Chemical control of downy brome, littleseed canarygrass and green foxtail in rapeseed in southern ıran

In order to investigate the effect of herbicide and choice of adjuvant on three grass weed species; downy brome (Bromus tectorum), littleseed canarygrass (Phalaris minor) and green foxtail (Setaria viridis); a greenhouse study was conducted in a factorial experiment laid out in randomized complete block design. Treatments included herbicide at five levels (propaquizafop, fluazifop-p-butyl, cycloxydim, sethoxydim and quizalofop-p-ethyl) each applied at two concentrations and either with/without adjuvant (volck or citoweet). The performance of herbicides and adjuvants was evaluated by rating the effect of treatment on an ordinal scale in each experimental unit at 10 and 20 days after planting (DAP). The results showed that herbicide efficiency rating distributions were significantly different between two times (10 and 20 DPA). Application of quizalofop-p-ethyl and propaquizafop were recorded as the best herbicide treatments in controlling the weeds used in this study 10DAP, however the difference between herbicides faded at 20 DAP. Also, no significant effect was found for concentration of herbicides and type of adjuvant. In addition, 30 days after herbicide application, maximum dry weight and leaf area of canola was recorded for cycloxydim, propaquizafop and quizalofop-pethyl, respectively whereas minimum dry weight and leaf area of canola was observed in pots sprayed with sethoxydim and fluazifop-p-butyl respectively

Screening Drought Tolerant Rapeseed Cultivars Using Yield and Physiological Indices

Rapeseed (Brassica napus) is an important source of edible oil worldwide. Rapeseed production is adversely affected by water deficit stress in drought prone areas. This study aimed to evaluate drought tolerance in seventeen rapeseed cultivars using yield and physiological indicators. The field experiment using two irrigation regimes was conducted on a silty loam soil at the research station of School of Agriculture, Shiraz University, Shiraz, Iran. In each irrigation treatment, the seventeen rapeseed cultivars with different origins were grown in a randomized complete block design with three replications. The normal irrigation and drought stress treatments were irrigated when 40% and 70% of available soil water capacity were depleted, respectively. The results revealed highly significant differences among the rapeseed cultivars for seed yield, and the various yield and physiological indices. The yield under normal and drought stress conditions showed significant correlations with stress tolerance index (STI), mean productivity (MP), geometric mean productivity (GMP), harmonic mean productivity (HMP) and modified stress tolerance index (MSTI) implying these indicators are able to identify the high yielding drought tolerant rapeseed cultivars. Based on the reliable yield indices, the three-dimensional plot and biplot analysis showed that the cultivars Karaj 1, NK Octans and Modena were the high yielding drought tolerant rapeseed cultivars. Generally, the drought tolerant cultivars showed high relative water content (RWC) under stress conditions, however there was no strong association between drought tolerance and RWC

Interrelationships between nitrogen rate and wild oat density on oilseed rape yield components

In order to evaluate the effect of nitrogen on oilseed rape yield and yield component under wild oat densities, a field experiment was conducted in Shiraz University, Iran, during 2008-2009 and 2009-2010 growing seasons. The experimental design was split plot with three replications. Treatments included four nitrogen levels (zero, 50, 100, and 150 kg ha-1 ) and four densities of wild oat (zero, 15, 30, and 45 plants m 2 ). The result showed that number of pods per main stem and secondary branches, number of seeds per main and secondary pods, 1000-seed weight, grain and biological yield was significantly increased by enhancement of nitrogen levels from zero to 150 kg ha-1 at weed-free treatments. Also, weed interference significantly reduced grain yield up to 41% under 50 and 100 kg ha-1 nitrogen application in comparison 150 kg ha-1 . Regardless of oilseed rape yield, weed dry weight was significantly increased with increasing the nitrogen levels, suggesting that high levels of nitrogen favor the crop over the weeds. This experiment suggested that oilseed rape grain and biological yield was affected more by high nitrogen levels at maximum weed density