RESULTS AND DISCUSSION
3.7 Nutrient assimilation in 2006 and 2007
3.7.6 Element mass per hectare in 2006
Table 3.38 Major and minor element mass of above ground plant parts ha-1. Average Mass Hectare-1 Element-1
recommended planting density for the cultivar used in this study. From the table it became clear that the plants kept on utilizing the major elements as it matured.
Maximum mass per element was reached at harvest. Comparing the masses at the mature head stage to harvest, it is evident that N, P and K increased about twofold in total mass ha-1, while Ca, Mg and S showed an approximate three fold increase in mass over the same period.
Comparing the mass ha-1 of the different major elements at mature head stage to values given in the nutrition guidelines for broccoli produced for the fresh market (Table 2.1 & Table 2.2) it appears that the level of N suggested to be applied is high compared to that which was found in this study. The Mayford guideline is 120 kg ha-1 but FSSA advises 160 to 260 kg ha-1. The number of plants per hectare which can be as high as 40 000, obviously is an important determining factor. When producing broccoli for seed this data shows that it is unlikely that more than 120 kg N ha-1 N is needed during the season till the mature head stage for this broccoli cultivar. Plant population and soil fertility would be important determining factors.
Phosphorus incorporation in the plants were low compared to the application rates recommended in Tables 2.1 and 2.2 which ranged from 40 kg ha-1 to 150 kg ha-1, while only 21.3 kg ha-1 at mature head and 35.5 kg ha-1 at harvest was incorporated in the plants in this study. If the whole plant (above ground) is removed, only 35.5 kg P would be removed per hectare during seed production.
The mass of K incorporated in the plants at mature head was 166.3 kg ha-1. This increased to 348.4 kg ha-1 at harvest. Application rates for K in Tables 2.1 and
2.2 for producing mature heads ranged from 60 kg to160 kg ha-1. Depending on the contribution of soil K, the recommended application rate of K up to mature head correlate with the amount that is removed per hectare. If all the above ground plant material is removed per hectare a relatively high quantity of K is removed.
Table 3.38 shows that the total mass of minor elements incorporated per hectare were small, but a large increase in total mass per hectare from mature head to the full flower and harvest stages for all elements became evident.
CONCLUSIONS
The different nutrient solutions applied in 2006 did not significantly affect the total biomass produced per plant. Total dry weight increased by 225% during the period of mature head to harvest.
In general plants did not respond significantly to the different nutrient solution treatments of 2006. Concentrations of elements as well as the mass of elements in plants were largely unresponsive. It appears likely that the total quantities of elements available to plants were still sufficient to negate any significant responses. During 2006 low levels of S and K in the nutrient solutions resulted in significantly lower concentrations in plants, but this did not translate into element mass per plant as well.
quantities of elements. The total major element mass that was incorporated ha-1 (21 000 plants ha-1) by the above ground plant parts were 173 kg N, 35.5 kg P, 348 kg K, 114 kg Ca, 30.5 kg Mg and 42.2 kg S. Comparing the masses at the mature head stage to harvest, one can see that N, P and K increased about twofold in total mass ha-1, while Ca, Mg and S showed an approximate three fold increase in mass over the same period.
An increase in concentration of both major and minor elements in the pods compared to the rest of the above ground plant parts at harvest were observed during 2007. An exception to this is K and Na concentration which were lower in the pods at harvest. This identifies the seed pods as strong sinks in plants.
In response to the Standard solution, the concentrations of major elements in plant parts at harvest and flowering stages in the same plant parts differed significantly when 2006 and 2007 is compared. This result supported that of Kopsell et al. (2004). The minor element concentrations of Na, Cu and Zn were essentially similar during 2006 and 2007.
Similar trends observed during 2006 and 2007 were increases in the concentrations of Ca, Mg and S in the top parts of the plant at harvest compared to full flower. This might have been a normal occurrence as less mobile elements tend to increase in concentration in older plant tissue as plants matured (Jones, 2000). For N, K and P there was an opposite effect with a decrease in concentration of the elements in the top part of the plant at harvest versus full flower.
REFERENCES
COERTZE, A.F., 1998. Besproeiing van koolgewasse, Roodeplaat Instituut vir Groente en Sierplante, G.2.
COMBRINK, N.J.J., 2005. Nutrient solutions and Greenhouse Management, ISBN 0-620-35295-7.
JONES, J. B. (jr). 2000. Laboratory guide for conducting soil tests and plant analysis. New York, USA: CRC Press.
JONES, J. B. (jr). 2003. Agronomic handbook: management of crops, soils and their fertility. New York, CRC Press LLC, Boca Raton, Florida.
KOPSELL, D.E., KOPSELL, D.E., LEFSRUD, M.G. & CURRAN-CELENTANO, J., 2004. Variability in elemental accumulations among leafy Brassica oleracea cultivars and selections. J. Plant Nutrition 27 (10), 1813-1826.
MARSCHNER, H., 1995. Mineral nutrition of higher plants. Academic Press, London.
PALZKILL, D.A., TIBBITTS, T.W. & WILLIAMS, P.H., 1976. Enhancement of calcium transport to inner leaves of cabbage for prevention of tipburn. J. Amer.
Soc. Hort. Sci. 101 (6), 645 – 648.
RAVEN, J.A. & SMITH, F.A., 1976. Nitrogen assimilation and transport in
vascular land plants in relation to intracellular pH regulation. New Phytologist 76, 415-431.
SAS, 2000. SAS/STAT Users Guide, Version 8, First Edition, Volume 2. SAS Institute Inc., Cary, NC, USA
SHAPIRO, S.S. & WILK, M.B., 1965. An analysis of Variance Test for Normality (complete samples), Biometrika 52, 591-611.
CHAPTER 4
THE INFLUENCE OF DIFFERENT NUTRIENT SOLUTIONS AND TREATMENTS ON SEED YIELD AND QUALITY CHARACTERISTICS OF BROCCOLI, Brassica oleracea L. var. italica Plenck SEED.
________________________________________________________________
M.L. du Randt
Department of Agriculture, Western Cape, Private Bag X1, Elsenburg, 7607
ABSTRACT
During 2006 and 2007 Broccoli plants were grown in trials for seed production in a net structure. The plants were grown in sand bags utilizing a drain to waste hydroponic system. The experimental design was a randomized complete block with 7 treatments replicated in four blocks. During 2006 seven nutrient solutions were utilized. The Standard solution was based on Steiner’s universal solution and different levels of N, S, K and Ca were used in the experimental solutions.
During 2007 the trial was continued and three of the 2006 solutions were used again including the Standard solution. Seven treatments were administered including foliar sprays with Ammonium Nitrate and Calcium Metalosate. One new nutrient solution was utilized during 2007. During both years the broccoli seed harvested were measured in terms of quality and quantity (yield). During 2006 no significant differences were found in terms of quality measurements. Yield plant-1 differed significantly with the four highest yielding solutions performing significantly better than the rest. The yields of these four did not differ significantly. During 2007 no significant differences were found for seed quality measurements, except for size (of the cotyledons) with three solutions performing equally in this measurement and significantly better than the rest. Yield plant-1 differed significantly with two nutrient solutions performing equally and significantly better than the other solutions. During both years the two best nutrient solutions in terms of yield plant-1 were the same. They were the Standard solution and Standard less K. The results indicate that no special adjustments need to be made to the Standard solution in order to produce good quality and quantity broccoli seed. Substantial differences in nutrient solution composition did not significantly affect the quality of broccoli seed produced. The yield per plant was significantly influenced by the composition of the nutrient solutions.
Key words: Brassica seed, Broccoli seed, Broccoli nutrition, Hydroponic production, Broccoli production.
INTRODUCTION
Over the past ten years the production of F1 hybrid broccoli and cauliflower seed has steadily increased in the Olifants river irrigation area of the West Coast. The seed crop is of considerable economic importance in the region.
Knowledge about the nutritional needs of broccoli plants grown for seed production is not known. Thorough knowledge and experience about production for fresh markets exist. Growers speculate that certain nutrients might be especially important for the production of high seed yields of good quality. The quantities and relation of these elements are not known.
Literature information concerning nutrition of seed producing cole crops is very scarce. In the Olifants river valley broccoli- and cauliflower seed have been produced for the past 10 years. Although no research has been done previously, the following plant nutrition program, based on practical experience, is used as a general guideline: 165 kg N ha-1;100 kg P ha-1; 400 kg K ha-1;160 kg Ca ha-1 (Pers. Comm., 2006: G.J. Kersop, PO Box 463, Lutzville).
Literature guidelines for the production of seed from Chinese cabbage indicate that supplying a sufficient amount of N at the initial stage of flowering is most effective in increasing seed yield. Side dressing of N at this stage is recommended. K also has to be supplied at this stage. B supplementation is also necessary where soil content is low. For artificially vernalized Chinese
weeks after planting. Further application of 30 kg N, 13 kg P and 16.6 kg K at bolting time with another side dressing at mid flowering time of 15 kg N and 8.3 kg K is suggested. Total N recommended was 195 kg ha-1. Borax at 10 kg ha-1 is applied before planting in cases of low B content (Opeña et al. 1988).
Research results (Mishra, 1992) showed that N fertilization had a significant effect on cauliflower plant height, number of branches, number and length of pods, number and weight of seeds and seed yield. It was found that the optimum level of N fertilization in that situation was 150 kg ha-1 and 10 kg ha-1 for B. This level also brought about maximum seed germination. The time of N application did not have any effect on seed yield or quality. In contrast Sharma and Rastogi, (1992) found that N fertilization at 200 kg ha-1 delivered the best yield of cauliflower seed per hectare. Different levels of boron application significantly affected number of branches, number of pods, 1000 seed weight and seed yield.
Lyons et al, (2009) investigated the response of Brassica rapa L. to a low dose of Selenium (as sodium selenite) in terms of growth responses and seed production. No change in total biomass was found but the Se treatment was associated with a 43% increase in seed production. It was further found that Se treated plants produced pollen that had 2% unviable grains compared to 14%
unviable grains for the control plants. Se-treated plants produced seed with a mean germination rate of 92% compared to a mean of 81% for the control.
(Terry et al., 2000). Se was not investigated in this study.
Through the utilization of different nutrient solutions in a hydroponic system with varying major element relations and content it was hoped to gain basic knowledge of broccoli seed quality and quantity responses to these variables. By varying the content of N, K, S and Ca in the nutrient solutions and studying seed quality and quantity results the aim was to gain understanding of the relative importance of the elements in relation to broccoli seed production.
MATERIAL AND METHODS
The research done was undertaken in conjunction with Syngenta Seed B.V., an international seed company. Research took place during two production seasons of 2006 and 2007. The same location, production system and structures as described in Chapter 3 were used during the two years of experimentation.