PROPERTIES OF PELLET AFFECTING SUGAR BEET SEED GERMINATION

Vlastnosti pelet ovlivňující klíčení řepného osiva

S. Podlaski

Warsaw Agricultural University (SGGW)

Summary: Profile of sugar beet seed and pellet water uptake, water diffusion coefficient and intensity of respiration of pelleted and naked seed after removing the pellet were presented. Pellets of sugar beet seeds differed in ability of water uptake and water diffusion coefficient. Speed of pellets water uptake affects pellet water potential. Strong correlations between water potential of pellet and speed of germination were observed.

Key words: seed, sugar beet, pellet

Souhrn: Cílem této práce bylo zjištění některých fyzikálních, fyzikálně-chemických a chemických vlastností pelet cukrovky od různých semenářských firem nabízejících osivo na polském trhu. Peletizované osivo cukrovky se liší svou schopností příjmu vody. Zjištěná vlhkost pelety z rašeliny byla dvakrát vyšší než u pelety složené z rašelinové drti. Vlhkost pelety však není pevně svázána s vlhkostí semene uvnitř pelety. Rozdíly ve vlhkosti pelety a semene uvnitř souvisí s vodním difuzním koeficientem pelety. Data z tabulky 2 indikují, že vysoká vlhkost pelety spojená s nízkým vodním difuzním koeficientem zaručuje podobný obsah vody v semeni uvnitř pelety jako při nízké vlhkosti pelety a vysokém koeficientu difuze. Dále byly zjištěny velké rozdíly ve vodním potenciálu pelet v průběhu klíčení. Klíčivost peletizovaných semen po 4 dnech koreluje s klíčivostí depeletizovaných semen a vodním potenciálem pelety po 24 hodinách od začátku klíčení. Podle rovnice regrese pokles vodního potenciálu pelety o -0,1 MPa znamená pokles klíčivosti o 2,25 % a zvýšení klíčivosti před peletizací o 1% zvyšuje klíčivost peletizovaného osiva o 1,07 %. Dýchání semen po depeletizaci bylo vyšší než u peletizovaných semen. Vyšší intenzita dýchání je pozitivně spojena s rychlostí klíčení. Značně velké diference mezi peletizovanými a depeletizovanými semeny stejné odrůdy nebo i mezi semeny stejného druhu různých odrůd byly zjištěny v klíčení ve stresových podmínkách. Při nedostatku nebo přebytku vody při klíčení byla intenzita dýchání některých peletizovaných a depeletizovaných semen velmi nízká. Toto vede k závěru, že vitalita peletizovaných semen je různá a typ pelety ovlivňuje kvalitu osiva. V souladu s dřívějšími výsledky některé peletizační procesy mohou negativně ovlivnit kvalitu “nahých” semen.

Klíčová slova: osivo, cukrovka, peleta

Introduction

Seed pelleting is a well-known way of sugar beet seed treatment. In Europe seed companies use own ways of seed pelleting or applied technologies worked out by specialized firms i.e. Suet, Germains.

Each pellet consists of pelleting substance (turf, wooden mill, vermiculit), glue and pesticides. Production of a good pellet is very difficult because in different thermal and moisture conditions pellets should performed in similar positive way.

The quality of pelleted seeds is determined by the vigour of ”naked seeds and properties of pellets. Only high vigour seeds should be used for pelleting. Thanks to it, possible negative effect of pelleting on the course of germination (i.e. speed of germination) can be reduced.

Number of published research on properties of pellets is very small because in most cases they are a commercial secret of the seed company.

Material and methods

The aim of research was determination of some physical, physical-chemical and chemical properties of pellets from different seed companies (8) offering seeds on the polish market. Beside that, the course of germination of pelleted and naked (after removing of pellets) was determined.

During the research the following properties were determined: crumble and rubbing resistance of pellets, water stability, swelling ability, chemical contents of some mineral components, seeds respiration activity, speed of water uptake of pellets, water potential, total and differentiated porosity of pellet. Among biological parameters the germination ability, speed and spread of germination were determined. In this paper some selected properties of pellets will be described.

Coefficient of the water diffusion of pellets was calculated on the basis of 6.52 Crank formula.

Gas analyser Li 6200, Licor company were used for estimation of seeds respiration activity X ray photographs were taken by Faxitron cabinet.

Results

Moisture contents of air dry pellets was very different. Table 1. Moisture content of peat pellet was 2 fold higher than pellet constituted from wooden mill. After 24 hrs since germination test start moisture content of pellets fluctuate from 23,0 to 40,5 % and after 3 days of germination from 28,6 to 40,2%. Moisture contents of pellet was not connected strictly with moisture of seed. Differences between moisture content of pellet and seed were greatest after 24 hrs of germination and fluctuates from 1,5 % to 21,1 %. This indicates, that there were some problems with water flow between the seed and the pellet.

Table 1. Water content ( % dry matter ) in pellet and seeds after one and three days of germination.

-	Water content ( % )
Companies	After
-	one day		three days
-	of germination
-	seeds	pellet	seeds	pellet
1	19,4	40,5	23,9	40,2
2	25,3	34,7	33,0	39,4
3	18,4	29,5	20,2	31,6
4	21,5	23,0	25,0	28,6
5	18,4	30,5	21,6	31,1
	20,6	31,6	24,7	34,2

Water diffusion coefficient of pellet was connected with differences in moisture contents of pellet and seed. Water diffusion coefficient, average for all varieties in time intervals of 0-24 hrs, 24-48 and 48-72 hrs amounted to 4,5, 3,0, and 1,18 x 10-3 cm2 d-1. The greatest differences were observed during the first day of germination among pellets belonging to different seed companies. Dates from table 2 indicate, that high moisture content of pellet connected with the low coefficient of diffusion guarantee similar water content of seed as well as low level of seed moisture and high water diffusion coefficient. of pellet.

Table 2. Diffusion coefficient of pellets of different seed companies in time intervals, since germination test start.

Moisture contents and water diffusion coefficient of pellet was connected with water potential. Great differences in pellet water potential was observed during germination among pellets belonging to different seed companies. Germination ability of pelleted seed, after 4 days of germination in optimal water conditions, (y) was correlated with germination of seeds after removing of pellets (x1) and water potential of pellets (x2) after 24 hrs since the start of germination. Equation of multiple correlation was following:

y = 1,07 x1 + 2,25 x2 R2 = 89%

Equation of regression indicate that decreasing pellet water potential by -0,1 MPa , decreased germination ability by 2,25 %. Simultaneously, increasing germination ability before pelleting by 1 %, increased germination ability pelleted seeds by 1,07 %.

Respiration of seeds after removing of pellet was higher than pelleted seed. Higher intensity of respiration was positively connected with the speed of germination. After 2 days since the start of the germination, germination ability of pelleted and unpelleted seeds for variety A amounted to 12,7 and 20,4 % and for variety B - 10,4 and 15,4 % respectively. Considerably greater differences for pelleted and unpelleted seeds of the same variety, or the same type of seeds of different varieties, were observed in stress conditions for germination. In shortage and excess water conditions in germination media, respiration intensity of some pelleted or unpelleted seeds was very low. It can be concluded that vigour of pelleted seeds is different and type of pellet affect the quality of the seeds in different ways. According to our last results, some pelleting processes can negatively affect the quality of the ”naked” seeds.

On photographs, 1 a-f , speed of water flow, trough pellet after 30-40 minutes since germination test start, was presented. The outer black layer of pellets indicate part of pellet saturated with water. Thanks to X ray technique and suitable contrasts, it was possible to observe and directly measure the area of saturated pellet and the speed of water movement inside pellet.

Table 3. Respiration intensity of pelleted and unpelleted (after removing of pellet) seeds germinated in optimal water condition (mg CO2 g-1 seeds weight).

Time of germination (h). Since germination test start	Varieties A Seeds			Varieties B Seeds
-	pelleted	unpelleted	-	pelleted	unpelleted	-
24	0,308	0,347	0,328	0,326	0,382	0,354
48	0,351	0,401	0,376	0,405	0,426	0,416
72	0,425	0,496	0,461	0,461	0,515	0,488
	0,361	0,415	0,397	0,397	0,441	-
NIR	0,026	0,035	0,041	0,033	0,036	-

Photo 1. Water movement through sugar beef pellet a,b,c,d,e,f - outer black layer of pellet saturated with water after a - 30 min., b,c,d - 35 min., e I f - 40 minutes of germination test start

Conclusion

1. Pellets of different seed companies had different ability of water uptake and water diffusion coefficient.

2. Water potential of pellet is positively correlated with germination ability after 4 days.

3. Pellet block intensity of respiration in comparison with unpelleted seeds.

4. X ray technique seems a very promising way for examination of water flow inside pellet.

References

1. Crank N:Mathematics of diffusion. Clarendon Press.1975.

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