756 



IOWA DEPARTMENT OF AGRICULTURE 



TESTING REDTOP SEED. 



In testing redtop seed it should be borne in mind that three grades 

 of this seed are offered in the trade under the names (1) "recleaned" 

 or "solid" seed, (2) "unhulled," and (3) "chaff" seed. The application 

 of these terms becomes evident when the structure of the seed is con- 

 sidered. The recleaned or solid seed consists of a mixture of free grains 

 and grains covered by the silvery, papery inner chaff. This is the best 

 matured, purest, and heaviest of the grades of redtop. The unhulled 

 grade consists chiefly of seed inclosed in the outer chaff. This seed is 

 generally more immature than the first grade. It also is lighter and 

 lower in purity than the other. Chaff redtop is a very variable grade 

 consisting largely or almost entirely of empty chaff scales and pieces 

 of stems, leaves, and other inert materials. Many samples of chaff red- 

 top contain very little solid seed. 



The recleaned grade is usually comparatively free from impurities, 

 but sometimes contains timothy to the extent of severe adulteration and 

 so should be tested in this respect. 



In making a practical test of the unhulled and chaff grades of redtop, 

 the lightest chaff may be blown carefully from the heaviest seed of a 

 quantity of seed of known weight. Some seeds will retain the inclosing 

 outer chaff. Slight rubbing will loosen this outer chaff, when it, too, 

 may be blown away, leaving the pure seed in essentially the same condi- 

 tion as shown in the recleaned grade. This seed, after removing the 

 ergot, timothy, and other foreign seeds, may then be weighed and its 

 quantity compared with the quantity of the original test sample. Such 

 a comparison sometimes shows a surprisingly small quantity of true seed 

 in chaffy grades. 



The purity of commercial red- 

 top seed is evidently dependent 

 on the trade grade and the ex- 

 tent to which the grades are 

 cleaned. The solid or recleaned 

 grade should show a purity of 

 95 to 98 per cent. The germina- 

 tion should be as high. The un- 

 hulled grade is more variable 

 " • • b both as to purity and viability. 



- . '.', The purity is influenced by the 



<^> '" '-.; - ._ -^1>-. \ widely variable quantity of brok- 



"rjf- ifjjg a en leaves, ergot, and loose chaff, 



and the viability varies because 

 of the practically worthless im- 

 mature and undeveloped grains 

 which constitute a variable pro- 

 portion of this grade of seed. 

 The noxious weed seeds found in redtop (chiefly in the chaffy grades) 

 include: Dock, tumbling mustard, rat-tail plantain, buckhorn, oxeye 

 daisy. 



^*^ a 



Fig-. 30. — Chaff of redtop seed; a, Whole 

 spikelets usually devoid of seed in 

 "chaffy" grades; b, separated scales 

 of the same; a and b represent the 

 outer chaff of the seed. (Enlarged.) 



