Foliar Boron Applications Increase the Final Number of Branches and Pods on Branches of Field-Grown Soybeans

Abstract

Our previous work demonstrated that boron (B) supplied to soybeans (Glycine max [L.] Merrill cv 'Williams 82') by a stem infusion technique increased the number of pods on branches and led to a significant yield increase. Therefore, research was continued to determine whether soil or foliar applications of B could be used to achieve the same results. Field experiments were completed with both soil and foliar applications of B. Only the foliar applications of B resulted in a significant increase in the number of pods/branch. When split foliar treatments were applied twice during flowering, the total application of 0.56 kilograms of B per hectare was the optimal treatment for increasing pods/branch. In a second field experiment in 1987, soybeans were treated weekly from flowering through podfill with six split foliar applications of aqueous H3B03 solutions so that total applications were either 0, 1.1, or 2.24 kilograms of B per hectare. Foliar applications increased the number of branches/plant at the end of the season and significantly stimulated the formation of pods on branches, with 1.12 kilograms of B per hectare being the optimal treatment for these variables. This rate also tended to increase the number of seeds/plant and seed yield/plant. A duplicate experiment with minor modifications was conducted during the summer of 1988, and again the 1.12 kilograms of B per hectare application rate resulted in significant increases in number of branches at harvest as well as number of pods on branches. The 2.24 kilograms of B per hectare application rate also significantly increased these parameters. Foliar B applications induced increases in leaf B concentration far above the 60 micrograms per gram level that was previously accepted as the upper level of tolerance for soybeans. Since optimal branching and per plant yield parameters were achieved by plants with B leaf concentrations greater than 160 micrograms per gram, the accepted range of soybean tolerance for B must be reconsidered when B is foliarly applied.

Role of Boron Nutrient in Nodules Growth and Nitrogen Fixation in Soybean Genotypes Under Water Stress Conditions

“…Recently, it was found that FB increased nodule weight under irrigated greenhouse conditions [43]. The current results showed that, even though B concentration in leaves was above the critical level (20 mg B kg -1 , critical level of B in leaves for normal plant growth) [44], FB resulted in a positive effect on seed and nodule weights, agreeing with previous research of those of [7,43,45]. Our results showed that foliar B increased grain weight, nodule mass and number due to the stimulatory effects of B on growth and development [9,11] and nodule improvement.…”

“…This indicated that both B and NO 3 stimulated NR enzyme somehow, maybe by facilitating nitrate availability in the cytoplasm to NR for reduction or enhancing nitrate translocation from the vacuoles to the cytoplasm, leading to higher NRA activity. This hypothesis was supported by the effect of B ion uptake [2,16] and the direct or indirect effects of B on the plasma membrane bound H+ ATPase (plasmalemma H+-ATPase activity) [7,17], cell wall structure and membrane integrity [2,7]. Our results are supported by [2] in that B may have an indirect influence on nitrate uptake and assimilation, and enhance NRA by inducing nitrate availability and increasing protein de novo synthesis as a result of nitrate absorption [49].…”

“…Our research demonstrated that foliar B application resulted in higher sucrose, glucose, and fructose under irrigated conditions, but under severe water stress these mono and disaccharides sugars decreased, but stachyose and raffinose increased (Table 6, 7,8).…”

“…Previous research indicated the involvement of B in cell wall structure [5,6]; cell membrane integrity [2,7]; sugar metabolism [2], especially sugar alcohols [3,8]; nitrogen assimilation and fixation [9,10]; nodules [11,12], nodullin protein (ENOD2) and malfunction of oxygen diffusion barrier [13]; phenolic metabolism [2,14,15]; ion uptake [2,16]; and plasma membrane-bount H+ ATPase [7,17,18].…”

Boron application in red clover (Trifolium pratense L.) seed production

“…Wilczek and Ćwintal (2008) found no significant effect of foliar B application in red clover during the bud formation stage on inflorescence number per stem. Schon and Blevins (1990) reported significantly more branches per plant and pods per branch in soybean as the result of B application at the onset of intensive growth. These results suggest that the effect of foliar-applied B on certain yield components is dependent on plant development stage during the treatment.…”