Photosynthetic attributes and seed yield of sunflower (Helianthus annuus L.) as influenced by different levels and ratios of nitrogen and phosphorus fertilizers

Abstract

A field experiment was conducted at the Main Research Station, University of Agricultural Sciences, Dharwad, India, on medium black soils during the kharif (wet) season of 1999. The experiment was laid out in a randomized complete block design with varying N/P ratios (0.67 to 2.00) along with a control with a constant level of potassium (60 kg ha -1). The results revealed that the number of green leaves plant -1 , the dry matter accumulation in the leaves, leaf area (dm 2 plant -1 ) and leaf area index (LAI) increased up to the flowering stage (65 DAS) and thereafter declined. In the early stages (seedling and button stages) there was no significant variation with respect to the number of green leaves plant -1 among the treatments except in the control. Similarly, leaf area and LAI did not vary at the seedling stage. Treatments receiving N/P ratios of >1.0 or 1.0 with higher doses of nitrogen (120 kg N ha -1 ) gave a significantly higher number of green leaves plant -1 , leaf area and LAI as compared to N/P ratios of <1.0 and the control in later stages. The dry matter accumulation in the leaves (g plant -1 ) differed in all the stages, but higher values were recorded in these same treatments. Thus, due to the higher number of green leaves, higher LAI and greater dry matter accumulation in the leaves, the treatments with an N/P ratio of >1.0 or 1.0 with 120 kg N ha -1 produced higher seed yields (3188 to 3554 kg ha -1 ) than other N/P ratios (2761 to 3009 kg ha -1 ). The highest yield (3554 kg ha -1 ) was recorded with an N/P ratio of 1.0 in the treatment receiving 120 kg N and 120 kg P 2 O 5 ha -1 . The correlation coefficients between these photosynthetic attributes and seed yield were also positive and significant.

Correlation between photosynthetic traits and yield in sunflower

“…Contrary to this experiment, Rawson and Turner (1983), Hall et al (1985) and Thavaprakash et al (2003) concluded that there was a close positive correlation between the LAI values and the yield of sunflower. The experimental data of this study proved a close negative correlation between LAI max and sowing date in 2013 and 2014 (r = -0.920**, r = 0.813**).…”

“…There was little assimilatory leaf area even from the end of August to the beginning of September in late sowing of sunflower (Figure 1). Sunflower cultivars gave their LAI max values in the flowering phenophases, which can be characterised by around 5.0 m 2 /m 2 as in the studies of Thavaprakash et al (2003) and Debaeke et al (2014). Cui et al (2000) proved that the rational increase of leaf area is a key crop physiological factor to increase the yields of sunflower.…”

Physiological role of exogenous nitric oxide in improving performance, yield and some biochemical aspects of sunflower plant under zinc stress

“…Sunflower (Helianthus annuus L.) is an important oilseed crop which ranks the third after soybean and peanut along with other oil seed crops like (canola and cotton) which contributes considerably to consumable oil in the world [31]. Sunflower occupies an important place in oil seed crops because of short duration as well as its ability to adapt wide range of climate and soil conditions [32]. This crop has an ideal place in the present cropping system but due to some constraints the average yield is much lower than world's average.…”