HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Abstract Full Text (PDF) Free Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in ISI Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (4) Citing Articles via Google Scholar Google Scholar Articles by Dordas, C. Search for Related Content PubMed Articles by Dordas, C. Agricola Articles by Dordas, C. Related Collections Crop Physiology & Metabolism Alfalfa Nutrient Management Plant Nutrition Seed Production

Production Papers

Foliar Boron Application Improves Seed Set, Seed Yield, and Seed Quality of Alfalfa

Aristotle Univ. of Thessaloniki, School of Agriculture, Lab. of Agronomy, University Campus, 54124 Thessaloniki, Greece

^* Corresponding author (chdordas{at}agro.auth.gr)

Received for publication December 26, 2005.

	ABSTRACT

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSIONS REFERENCES

 
Alfalfa (Medicago sativa L.) is one of the most important forage crops worldwide because of its good forage quality and high adaptability. Seed yield is generally considered to be of secondary importance and is characterized by fluctuating yields with often poor seed yield and seed quality. A field study was conducted to determine if foliar B applications during anthesis increase seed set, seed yield, yield components, and improves seed quality in alfalfa. Boron solutions were applied at four rates (0, 400, 800, and 1200 mg B L^–1) to field plots exhibiting no vegetative symptoms of B deficiency. Foliar B application increased the percent of pods formed per inflorescence by up to 52% compared with the control and there was no statistical significant difference between the three rates of B. The seed yield was increased by an average of 37 % compared with the control during the 2 yr and in both locations. Moreover foliar application with B improved seed germination and increased seed vigor which was increased by 27% in 2003 and up to 19% in 2004 compared with the untreated control. The 400 mg B L^–1 treatment was found to have a positive response in most characteristics. The results obtained here suggest that the critical B levels for alfalfa used for forage production is below that for seed production and foliar B application can improve the seed yield and seed quality of alfalfa grown for seed production.

Abbreviations: AA, accelerated aging • a.i., active ingredient • HI, harvest index

	INTRODUCTION

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSIONS REFERENCES

 
ALFALFA is grown worldwide as a forage crop because of its good forage quality, high forage yield over a wide range of environments, and high adaptability (Iannucci et al., 2002). Alfalfa is grown mainly for forage production and seed yield is considered to be of secondary importance (Iannucci et al., 2002). In many countries, farmers produce their seeds directly, harvesting them from the crop regrowth following the first cut of herbage during the last year of the crop (Falcinelli and Martiniello, 1998). The above practice has the advantage that the income for the farmer can be increased. The seed yield is quite variable ranging from 60 to 660 kg ha^–1 (Iannucci et al., 2002). Another problem associated with the seed production is the poor seed quality. High-quality seeds with high vital quality are essential for obtaining successful stands under all conditions with high forage quality.

Seed yield is a complex trait as it is the product of several individual yield components (number of seeds per plant, number of inflorescences per plant, number of pods per inflorescence, number of pods per plant, number of seeds per inflorescence, seed weight per pod, seed weight per inflorescence and mean seed weight) (Yassin, 1973). Seed yield is often low compared with other species because of lack of pollination under natural conditions, pod abortion, and the production of only a few seeds per pod (Gender et al., 1997). There are many factors that influence seed yield and seed quality such as genotype, agronomic techniques, and the environment. Seed quality is reflected in seedling density, seedling vigor, the competitiveness, and uniformity of crop growth (Hampton, 1991). It is important to determine the appropriate agronomic factors that optimize both seed yield and quality as proposed by Hampton (1991).

Although, alfalfa is well adapted to a wide range of growing conditions and soils, nutritional disorders caused by B deficiency are quite common (Shorrocks, 1997; Dell and Huang, 1997). Boron deficiency in alfalfa causes leaf yellowing and reddening of the upper leaves. The internodes of the top growth become progressively shorter and the short branches help to give the plant a rosette appearance. At this stage the growing point becomes dormant or dies, flowering is reduced and the flower falls before setting seed (Shorrocks, 1997; Bell, 1997).

Alfalfa is B deficient when B concentration at the top 15 cm of the plant is below 30 mg kg^–1 while when B concentration is between 30 and 80 mg kg^–1 alfalfa is considered B sufficient (Bergmann, 1992). Between these two categories plant performance is not clearly defined, while the rather broad adequacy range is difficult to interpret. These critical values were determined on visual symptoms and not on yield response especially in crops grown for seed production (Bergmann, 1992). Symptoms of nutrient deficiency, however, often become clearly visible only after a deficiency is acute and growth and yield are already severely depressed (Marschner, 1995; Bell, 1997). There are several reports in a number of crops which demonstrated that B can be deficient and have a significant effect on yield even when there are no vegetative signs of deficiency and even when B concentration is at the adequate range (Perica et al., 2001; Nyomora et al., 1999; Hanson, 1991; Asad et al., 2003). A number of previous studies have increased the significance of the role of foliar nutrient application on the productivity of the plant (Asad et al., 2002, 2003; Nyomora et al., 1997; Perica et al., 2001).

It is commonly accepted that floral and fruiting organs are especially sensitive to B deficiency (Brown et al., 2002; Dell and Huang, 1997; Dell et al., 2002). In many crops there is much higher demand for B during flowering and seed set even in crops where the B levels in leaves are in the adequate range. It was reported that there was an increase in fruit set and yield with B foliar applications (Nyomora et al., 1999; Perica et al., 2001; Asad et al., 2003).

Alfalfa has high requirements for B, and many times B is applied as soil or foliar application (Razmjoo and Henderlong, 1997; Walker et al., 1987). This application is used mainly to correct or control B deficiency in the vegetative parts. However, there is very little information regarding the reproductive requirements for B of alfalfa and also the effect of B application on flowering, pod and seed set, pod abortion, pod and seed development, and seed quality.

Since alfalfa has high requirements for B and also there is a high requirement for B at the reproductive stage, it was hypothesized that foliar B applications could increase fruit and seed set, seed yield, and also improve the seed quality. The objectives of this study were to determine the effect of foliar B application on pod development, pod set, seed set, seed yield, yield components (pod number per inflorescence, seed number per pod, seed development, seed weight), and on seed quality (seed germination and seed vigor).

	MATERIALS AND METHODS

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSIONS REFERENCES

 
The experiments were performed at the experimental farm of the Aristotle University of Thessaloniki, Greece during the 2002–2003 (2003) and 2003–2004 (2004) growing seasons. The farm is located in northern Greece (22°59'6.17'' N, 40°32'9.32'' E) at the sea level. During the 2004 growing season, another experiment was conducted in a farm located in the county of Serres which is in northern Greece (23°86.1'11.1'' N, 41°28'1.6'' E) 180 m above sea level. The second location was selected as it is one of the major growing areas of alfalfa in Greece and to repeat the experiment in a different location. The cultivar was Iliki which is widely used in Greece. The crop was at its second year when the experiments were started. The soil type where the experiment took place was a calcareous loam (Typic Xerorthent). Weather data (rainfall and average, maximum, and minimum temperatures) were recorded daily and are reported as mean monthly data for the 2 yr (Table 1). The experimental design was a randomized complete block design with four treatments (0, 400, 800, 1200 mg B L^–1) and five replications. Boron was applied during flowering (when 50% of the plants were at anthesis) as foliar applications. The experimental plots were 5 by 3 m. Boron was applied in the form of Solubor containing 20% of B (Na₂B₈O₁₃ 4H₂O, US Borax, Boron, CA). The foliar application was conducted using an AZO portable field plot sprayer (AZO, Ede, the Netherlands) at 250 kPa pressure and applying 1000 L of water ha^–1. Boron foliar application took place on the 2 June 2003 during the 2003 and on the 6 June 2004 (Thessaloniki) and on the 11 June 2004 (Serres).

The following parameters were determined: concentration of B at the top 15 cm of alfalfa tissues (stems, leaves, and flowers), percent of flowers which formed pods, number of pods formed per inflorescence, number of seeds per pod, average seed weight, seed weight per pod, seed weight per inflorescence, harvest index, percent of normal and shrunken seeds, seed yield, seed quality determined as standard germination and accelerated aging (AA).

Determination of Boron Content
Alfalfa tissues (the top 15 cm) were sampled 7 d after the foliar application. Plant tissues were washed for 1 min in deionized water, dried at 60°C in a forced air oven for 3 d and ground to pass a 30-mesh screen. One gram of tissue was placed in a porcelain crucible for ashing at 500°C overnight. The ashed samples were then extracted with 20 mL of 2 nM HCl at 90°C for 10 min, and after filtration the samples were transferred to plastic vials. Then 2 mL of the solution was added to 4 mL of buffer solution (containing 25% ammonium acetate, 1.5% EDTA, and 12.5% acetic acid) and 4 mL of azomethine-H solution containing 0.45% azomethine-H and 1% of ascorbic acid prepared right before the analysis (John et al., 1975). The color was left to develop for at least 45 min and the amount of B was determined using a spectrophotometer at 420 nm (PerkinElmer, Fremont, CA).

Effect of Boron on the Development of Pods
Ten inflorescences were tagged right before the foliar application and the number of flowers were counted and recorded. When the pods were ready for harvest the number of pods was measured and the percent of flowers which formed pods was determined.

Twenty pods per plot were used to determine the number of seeds per pod. Also, the percent of normal (well-developed) and shrunken seeds were determined in 20 pods per plot randomly selected from the upper and the lower part of the stem.

Final Yield
For the determination of the total yield 2 m² were cut, the stems were left to dry in the field for 2 d. Then they were collected, weighed, and a 500-g sample from each plot was dried in an air-forced oven at 60°C for 3 to 4 d to determine the water content of each sample. The water content of each sample was then used to determine the final dry weight of each sample and this final dry weight was used for the calculation of the harvest index. The seed was collected using a harvesting machine and then cleaned. Seed yield was calculated at 13% standard moisture content (kg ha^–1). Harvest index (HI) was calculated as the percentage ratio of seed weight to the total aboveground dry biomass of the 2 m². The cleaned seeds where stored at 4°C.

Effect of Boron on Seed Quality
Seed quality was evaluated by germination and vigor test. Germination tests were performed at room temperature (25°C) in plastic Petri dishes with a filter paper Whatman No.1 and 5 mL of double deionized (D-D) water. Two replicates of 100 seeds from each plot were used. Germinated seeds with emerged radicles at least 2 mm were counted after 5 d. Water was added when the Petri dish was getting dry.

Vigor assay was done using the AA test (Iannucci et al., 2002). Briefly 100 seeds from each plot were placed at 40°C and 100% relative humidity for 72 h and the germination was tested as described before using two replicates of 50 seeds each.

Statistics
The experiments were performed into two consecutive years (2003 and 2004) in one location and during the second year (2004) a second location was used. Statistical significance was determined with analysis of variance (ANOVA). Analyses were performed with a personal computer using the SPSS software (SPSS, Chicago, IL). The difference was significant when P < 0.05.

	RESULTS

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSIONS REFERENCES

 
The weather conditions during the 2003 and 2004 growing seasons were quite different and this had a significant impact on the results (Table 1). The 2003 season was characterized by a warm and dry summer, whereas in 2004 there was quite significant rainfall during the summer (July and August). Weather conditions affected the seed yield and harvest index more in the 2003 than in the 2004 growing season (Table 1).

Effect of Boron Application on Tissue Boron Concentration
Boron concentration of the plants top 15 cm (38 mg kg^–1) was above the adequate level of 30 mg kg^–1 at 0 applied B rate and it increased with increasing B rate up to 82 mg kg^–1 of B at 1200 mg B L^–1 (Table 2). Similar results were obtained also during the second year and at both locations (Thessaloniki, Serres) (Table 2). In Serres during the 2004 growing season B concentration was 28 mg kg^–1 which is slightly below the adequate level of 30 mg kg^–1.

Effect of Boron Application on Seed Number per Pod, Mean Seed Weight, Seed Weight per Pod, and Seed Weight per Inflorescence
Foliar B application did not affect the number of seeds per pod in both years at Thessaloniki. At the second location (Serres) the number of seeds per pod was increased by 22% over the three application rates compared with the control treatment (Table 4). In 2004 the number of seeds per pod was greater compared with the previous year (1.85 in 2003 and 2.46 in 2004 at 0 mg B L^–1).

Boron application affected the seed weight per inflorescence. At 400 mg B L^–1 there was the highest increase up to 72% compared with the 0 mg B L^–1 treatment while at the other treatments there was no difference in 2003. This is mainly attributed to the highest number of pods at this treatment. During the 2004 growing season in Thessaloniki there was an increase of 29, 26, and 31% and in Serres there was an increase of 43, 68, and 52% at 400, 800, and 1200 mg B L^–1, respectively compared with the control treatment (Table 4).

Effect of Boron Application on Seed Yield, Harvest Index, and Weight of One Thousand Seeds
Boron application increased seed yield at both years and at both locations. Seed yield was increased by 46% at the 400 mg B L^–1 rate compared with the control treatment during 2003 and there was no increase at the higher B rates. During the second year there was an average increase of 34% with the addition of supplemental B in Thessaloniki and 32% in the second location (Serres) compared with the control treatment (Table 5).

The weight of 1000 seeds did not differ between the different treatments. The only exception was at Thessaloniki during 2004 at 1200 mg B L^–1 where there was an increase of 9%. Between the different locations and different years there were differences since in 2003 the weight of 1000 seeds was slightly higher than in 2004 in Thessaloniki while in Serres the weight of 1000 seeds was similar with the 2003 in Thessaloniki (Table 5).

Effect of Boron Application on Seed Development
Boron application affected seed development especially during the first year of the study. There was an increase in the number of the well-developed seeds compared with the shrunken seeds when B was applied compared with the control treatment. As B concentration increased there was an increase of the normal (well-developed seeds) from 28.16% at 0 mg B L^–1 up to 31.86, 46.63, and 45.82% at 400, 800, 1200 mg B L^–1, respectively (Table 6). In contrast to the first year during the second year the seed development was not affected, as there was not any statistical significant difference at the different rates of B. This mainly is attributed to the greater variability between the different treatments. The percent of well-developed seeds during the 2004 was higher 60% compared with 27% during the 2003 at the 0 mg B L^–1.

	DISCUSSION

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSIONS REFERENCES

The average B concentration in control plants was above the current recognized adequate level of 30 mg kg^–1. Despite the fact that B was at the adequate level for forage production there was a significant effect on seed yield and seed quality when B was applied. These findings suggest that the critical level of B for alfalfa is lower when alfalfa is used for forage production compared when it is used for seed production. The fact that B has a beneficial effect on seed production has been observed with other crops such as white clover (Trifolium repens L.), soybean [Glycine max (L.) Merr.], canola (Brassica rapa L.), and sunflower (Helianthus annuus L.) (Schon and Blevins, 1990; Johnson and Wear, 1966; Asad et al., 2002, 2003). The fact that in most characteristics which were studied there was no further response above the 400 mg B L^–1 indicates that there was a need for B which was covered by the first rate of B (400 mg B L^–1) and there was no further effect with the higher rates that were used. It is possible that the optimum B rate might be between 0 and 800 mg B L^–1 and more research is needed to find the optimum B concentration.

The significant effect that B had on seed yield indicates that B plays an important role in seed formation in alfalfa. Alfalfa has high requirements for B and it is possible since the flowering process and the reproductive tissue have higher requirements for B that B foliar application can have a direct effect on seed yield. It is also possible that the current critical B value for alfalfa (30 ppm) is not the actual critical value especially when alfalfa is grown for seed production. Since in alfalfa B is immobile it will require B during flowering and seed development from direct uptake from the roots (Brown and Shelp, 1997). A major constrain of B movement taken up from the roots is that the xylem connection between seed and mother tissue is not well developed (Dell et al., 2002). Since flowers and seeds do not transpire as much as leaves it might not be able to take up B directly from the soil. This is one of the possible reasons why in many studies there was a significant effect of foliar B application on seed and fruit yield (Perica et al., 2001; Schon and Blevins, 1990; Johnson and Wear, 1966; Asad et al., 2002, 2003).

Boron significantly influenced the percent of pods formed per inflorescence. This suggests that B has a direct effect on fertilization and especially on pod formation in alfalfa. The reason for the higher percent of pods per inflorescence in response to B application is attributed to the fact that the number of flowers at the treated plots was slightly smaller. However, because of the variability of the data the differences were not significant between the different treatments (data not shown). One of the major problems in alfalfa seed production is pod abortion (Hacquet, 1990). Pod abortion is attributed to assimilate distribution, however the causes are not known (Gender et al., 1997). The present study indicates that B can play a significant role in pod abortion. Application of B during anthesis in alfalfa significantly increased the number of pods formed per inflorescence by up to 63% at 400 mg B L^–1 treatment compared with the control treatment. This increase in the number of pods per inflorescence improves the potential for increased seed yield. Similar results were reported in black gram [Vigna mungo (L.) Hepper] and soybean, where B deficiency decreased the number of pods per inflorescence (Rerkasem et al., 1997; Bell et al., 1990).

Boron rate of 400 mg B L^–1 were effective in most cases in increasing the seed weight per pod, and seed weight per inflorescence especially during the second year in both locations. It was found that B deficiency reduces the number of seeds per pod and also increases the seed abortion in black gram (Rerkasem et al., 1997). In alfalfa there was no effect on mean seed weight since seed size in legumes mainly depends on genetic factors (Bolanos-Aguilar et al., 2000, 2002). However, under B deficiency it is possible that the seed size will be decreased as it was found in peanut (Arachis hypogaea L.) (Keerati-Kasikom et al., 1991). In contrast to peanut in other species (wheat and subterranean clover [Trifolium subterraneum L.]) it was found that B deficiency increases seed size (Rerkasem and Loneragan, 1994; Dear and Lipsett, 1987). The response that was found in this study is probably due to the fact that alfalfa plants were stressed by B deficiency and there was no change in seed size. Higher rates of B did not affect seed yield and yield components indicating that a small increase in B concentration was adequate in increasing seed yield. The higher B concentrations that can be used can have a negative effect (toxicity) as it was reported in other studies (Perica et al., 2001; Nyomora et al., 1999). The seed weight per pod and the seed weight per inflorescence were affected by B application especially during the second year of the study. Both characteristics are important yield components and are influenced by genotype, environmental conditions, and cultural practices (Bolanos-Aguilar et al., 2000, 2002).

The seed yield was increased up to 50% with B application compared with the control treatment following the increase in the number of pods formed per inflorescence. From the present data we can conclude that B application of 400 mg B L^–1 is beneficial for alfalfa plants with a B concentration of 44 mg kg^–1 or lower and can result in an increase in seed yield of up to 50%. There was much higher increase in 2004 than in 2003 probably because 2003 was warmer and drier compared with the 2004 growing season. Boron has direct function on flowering, pollen germination and growth, seed, and fruit formation. There are still many unanswered questions on how B acts in increasing seed yield and its components and also how B moves into the flowers and into the developing fruits and seeds (Dell et al., 2002). One possibility is that the foliarly applied B can affect fertilization, seed and pod development, and increase the seed yield. It can reduce pod abortion which is one of the most significant problems in alfalfa seed production (Bolanos-Aguilar et al., 2002; Gender et al., 1997).

Harvest index is an important factor of how vegetative mass (biomass) is allocated to seed at maturity. In the present study there was a significant effect of B on harvest index as it increased with B foliar application. This is probably because B application increased seed yield but had little effect on the total biomass (data not shown) as seed weight is only a small fraction of the total biomass of alfalfa crop (Bolanos-Aguilar et al., 2002).

Seed germination and seed vigor were also affected by B application from the first rate of B there was a significant increase in standard seed germination. The effect of B was much higher in seed vigor compared with the seed germination. This is in agreement with the suggestion that seeds that were developed in plants with adequate nutrient supply show high germination percentage and also have high seed vigor (Welch, 1999). Seed vigor and germination are important characteristics for obtaining successful stands under all conditions with high yield and quality (Bolanos-Aguilar et al., 2000, 2002; Iannucci et al., 2002; Steiner et al., 1992). The fact that B application increased seed vigor indicates that seeds with adequate B supply can germinate and produce seedlings with better ability to grow and withstand any adverse environmental conditions. The effect that B had on seed germination can be because B deficiency causes embryo defect such as hallow heart in peanut and fruit abnormalities (Harris and Brolmann, 1966a, 1966b). It was found that in B-deficient seeds during germination there is an increase in the abnormal seedlings and a decrease in germination percentage (Bell et al., 1989, 1990; Rerkasem et al., 1997). This effect was reversed by supplemental B which enhanced seed germination and seed vigor (Bell et al., 1990; Rerkasem et al., 1997).

	CONCLUSIONS

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSIONS REFERENCES

 
Foliar B application had a significant effect on seed yield and seed germination of alfalfa in both years and in both locations during the second year. The effect of B on yield can be attributed to affecting the number of pods per inflorescence and the seed weight per inflorescence. A major finding of the present study is that the critical levels of B used for forage production is below that for seed production. Foliar application with 400 mg B L^–1 can have a positive effect on seed yield and on seed quality. The results presented here provide some clear guidelines for developing more productive alfalfa seed production and with better quality.

	REFERENCES

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSIONS REFERENCES

 

• Abu-Shakra, S., M.L. Bhatti, and H. Ahmed. 1977. Effect of forage harvest frequency on subsequent alfalfa seed production and pollen quality. Agron. J. 69:428–431.[Abstract/Free Full Text]
• Asad, A., F.P.C. Blamey, and D.G. Edwards. 2002. Dry matter production and boron concentrations of vegetative and reproductive tissues of canola and sunflower plants grown in nutrient solution. Plant Soil 243:243–252.
• Asad, A., F.P.C. Blamey, and D.G. Edwards. 2003. Effects of boron foliar applications on vegetative and reproductive growth of sunflower. Anal. Bot. 92:565–570.
• Bell, R.W. 1997. Diagnosis and prediction of boron deficiency for plant production. Plant Soil 193:149–168.
• Bell, R.W., L. McLay, D. Plaskett, B. Dell, and J.F. Loneragan. 1990. Internal boron requirements of green gram (Vigna radiate). p. 275–280. In M.L. Van Beusichem (ed.) Plant nutrition-physiology and application. Kluwer Academic Publ., Dordrecht, the Netherlands.
• Bell, R.W., L.D. McLay, D. Plaskett, B. Dell, and J.F. Loneragan 1989. Germination and vigor of black gram (Vigna mungo L. Hepper) seed from plants grown with and without boron. Aust. J. Agric. Res. 40:272–279.
• Bergmann, W. 1992. Nutritional disorders of plants color atlas. p. 386. Gustav Fischer Verlag Jena, Stuttgart.
• Bolanos-Aguilar, E.D., C. Huyghe, D. Djukic, B. Julier, and C. Escalle. 2000. Genetic control of alfalfa seed yield and its components. Plant Breed. 120:67–72.
• Bolanos-Aguilar, E.D., C. Huyghe, C. Escalle, J. Hacquet, and B. Julier. 2002. Effect of cultivar and environment on seed yield in alfalfa. Crop Sci. 42:45–50.[Abstract/Free Full Text]
• Brown, P.H., N. Bellaloui, M.A. Wimmer, E.S. Bassil, J. Ruiz, H. Hu, H. Pfeffer, F. Dannel, and V. Romheld. 2002. Boron in plant biology. Plant Biol. 4:205–223.
• Brown, P.H., and B.J. Shelp. 1997. Boron mobility in plants. Plant Soil 193:85–101.[CrossRef]
• Dear, B.S., and J. Lipsett. 1987. The effect of boron supply on the growth and seed production of subterranean clover (Trifolium subterraneum L.). Aust. J. Agric. Res. 38:537–546.
• Dell, B., and L. Huang. 1997. Physiological response of plants to low boron. Plant Soil 193:103–120.[CrossRef]
• Dell, B., L. Huang, and R.W. Bell. 2002. Boron in plant reproduction. p. 103–117. In H.E. Goldbach et al. (ed.) Boron in plant and animal nutrition. Kluwer Academic/Pledum Publ., New York.
• Falcinelli, M., and P. Martiniello. 1998. Forage seed production in Italy. J. Appl. Seed Prod. 16:61–66.
• Gender, T., E. Deleens, and A. Fleury. 1997. Influence of photosynthetic restriction due to defoliation at flowering on seed abortion in lucerne (Medicago sativa L). J. Exp. Bot. 48:1815–1823.[Abstract/Free Full Text]
• Hacquet, J. 1990. Genetic variability and climatic factors affecting lucerne seed production. J. Appl. Seed Prod. 8:59–67.
• Hampton, J.G. 1991. Herbage seed lot vigour. Do problems start with seed production? J. Appl. Seed Prod. 9:87–93.
• Hanson, E.J. 1991. Sour cherry respond to foliar boron applications. HortScience 26:1142–1145.[Abstract/Free Full Text]
• Harris, H.C., and J.B. Brolmann. 1966a. Comparison of calcium and boron deficiencies of the peanut: I. Physiological and yield differences. Agron. J. 58:575–578.[Abstract/Free Full Text]
• Harris, H.C., and J.B. Brolmann. 1966b. Comparison of calcium and boron deficiencies of the peanut: II. Seed quality in relation to histology and viability. Agron. J. 58:578–582.[Abstract/Free Full Text]
• Iannucci, A., N. Di Fonzo, and P. Martiniello. 2002. Aflalfa (Medicago sativa L.) seed yield and quality under different forage management systems and irrigation treatments in a Mediterranean environment. Field Crops Res. 78:65–74.[CrossRef]
• John, M.K., H.H. Chuah, and J.H. Neufeld. 1975. Application of improved azomethine-H method to the determination of boron in soils and plants. Anal. Lett. 8:559–568.
• Johnson, W.C., and J.I. Wear. 1966. Effect of boron on white clover (Trifolium repens L.) seed production. Agron. J. 59:205–206.
• Keerati-Kasikom, P., R.W. Bell, and J.F. Loneragan. 1991. Response of two peanut cultivars (Arachis hypogaea) to boron and calcium. Plant Soil 138:61–66.
• Marschner, H. 1995. Mineral nutrition of higher plants. p. 379–395. Academic Press, London.
• Medeiros, R.B., A.V.A. Jacques, and C. Nabinger. 1995. Alfalfa (Medicago sativa L.) seed production under different row spacing and plant population in the seeding year. p. 331–335. In W. Schøberlein (ed.) Yield and quality in herbage seed production. Proc. of the 3rd Int. Herbage Seed Conf., Halle (Sale), Germany. 18–23 June. Martin Luther Univ., Wittenberg, Halle, Germany.
• Nyomora, A.M.S., P.H. Brown, and M. Freeman. 1997. Fall foliar-applied boron increases tissue boron concentration and nut set of almonds. J. Am. Soc. Hortic. Sci. 122:405–409.[Abstract/Free Full Text]
• Nyomora, A.M.S., P.H. Brown, and B. Krueger. 1999. Effects of rate and time of boron application on almond tissue B concentration and productivity. HortScience 34:242–245.[Abstract/Free Full Text]
• Perica, S., P.H. Brown, J.H. Connell, A.M.S. Nyomora, C. Dordas, H. Hu, and J.C. Stangoulis. 2001. Foliar boron application improves flower fertility and fruit set of olive. HortScience 36:714–716.
• Razmjoo, K., and P.R. Henderlong. 1997. Effect of potassium, sulfur, boron, and molybdenum fertilization on alfalfa production and herbage macronutrient contents. J. Plant Nutr. 20:1681–1696.
• Rerkasem, B., R.W. Bell, S. Lodkaew, and J.F. Loneragan. 1997. Relationship of seed boron concentration to germination and growth of soybean (Glycine max). Nutr. Cycling Agroecosyst. 48:217–223.
• Rerkasem, B., and J.F. Loneragan. 1994. Boron deficiency in two wheat genotypes in a warm, subtropical region. Agron. J. 86:887–890.[Abstract/Free Full Text]
• Schon, M.K., and D.G. Blevins. 1990. Foliar boron applications increase the final number of branches and pods on branches of field–grown soybeans. Plant Physiol. 92:602–607.[Abstract/Free Full Text]
• Shorrocks, V.K. 1997. The occurrence and correction of boron deficiency. Plant Soil 193:121–148.[CrossRef]
• Steiner, J.J., R.B. Hutmacher, S.D. Gamble, J.E. Ayars, and S.S. Vail. 1992. Alfalfa seed water management: I. Crop reproductive development and seed yield. Crop Sci. 32:476–481.[Abstract/Free Full Text]
• Walker, W.M., D.W. Graffis, and C.D. Faulker. 1987. Effect of potassium and boron upon yield and nutrient concentration on alfalfa. J. Plant Nutr. 10:2169–2180.
• Welch, R.M. 1999. Importance of seed mineral nutrient reserves in crop growth and development. p. 205–226. In Z. Rengel (ed.) Mineral nutrition of crops fundamental mechanisms and implications Food Product Press, New York.
• Yassin, T.E. 1973. Genotypic and phenotypic variances and correlations in field beans (Vicia faba L). J. Agric. Sci. 81:445–448.

This article has been cited by other articles:

				T. Zhang, X. Wang, J. Han, Y. Wang, P. Mao, and M. Majerus Effects of Between-Row and Within-Row Spacing on Alfalfa Seed Yields Crop Sci., March 19, 2008; 48(2): 794 - 803. [Abstract] [Full Text] [PDF]

This Article Abstract Full Text (PDF) Free Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in ISI Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (4) Citing Articles via Google Scholar Google Scholar Articles by Dordas, C. Search for Related Content PubMed Articles by Dordas, C. Agricola Articles by Dordas, C. Related Collections Crop Physiology & Metabolism Alfalfa Nutrient Management Plant Nutrition Seed Production