Seed and Grain Quality

this unit of study deals with seed and green quality it will cover basic principles and procedures of identifying and analyzing quality of seed for planting purposes and for food and feed utilization seed quality refers to those factors affecting the suitability of seed for planting purposes grain quality refers to those factors affecting the suitability of grain for food feed or industrial purposes the first section of the unit deals with seed quality using high quality seed for planting is extremely important because it is one of the first requirements for establishing productive weed free stands of high yielding crops for seed quality can result in non-uniform poor and slow emerging stands this can make the crop more susceptible to seed and seedling diseases skips or open areas in the stand can be dominated by weeds which can further reduce yields during the rest of the growing season good seed quality also includes other factors such as varietal purity and freedom from weed seeds other crop seeds and foreign material all of these factors can hinder the first goal in crop production which is to obtain uniform vigorous growing young crop plants seeds used for planting must be viable and high in vigor viable seeds are those that have the ability to germinate seeds with high vigor are those that have the capacity to produce strong rapidly emerging seedlings thus high-quality seeds germinate better and produce more vigorous see Germany leans than poor quality seeds the next topic for study is the section on seed germination you should now stop the VCR and study this section in your text then return to the VCR for further tutoring although seeds may be viable germination may not occur because of some internal factor of the seed or the lack of some necessary environmental condition required for germination seed dormancy refers to the condition where viable seeds do not germinate when favourable germination conditions are present seed dormancy is frequently caused by physical or physiological factors of the seed an example of physical dormancy is hard seed coats the seed coat of some species like alfalfa and other forage legumes can physically impede the movement of oxygen or water into the seed which is necessary for germination to proceed Scarah fication or artificially altering the seed coat to increase permeability is often used to overcome seed dormancy due to hard seed coats Scarah fication may be accomplished by mechanical abrasion or by chemical treatment of seed coats using weak acids or other materials physiological dormancy may be due to hormonal inhibition or in mature embryos present in seed of some species crops like barley and wheat frequently have short term physiological seed dormancy this is caused by hormonal imbalances of germination inhibitors and promoters present in the seed a short period of storage or after ripening is needed to alleviate dormancy and obtain maximum germination potential even viable non-dormant seeds may not germinate if external requirements for germination are not present external requirements vary among crop species and include correct oxygen moisture and temperature in some species light is required for maximum germination potential however most of the major crops do not require light for germination the conditions of the seed bed can influence germination by influencing the micro environment surrounding the seed for example waterlogged soils maybe too low in oxygen content for proper germination soil temperatures at early planting dates or under heavy surface crop residues may be too low for maximum germination in sandy soils or in later planting dates soil moisture may limit germination seed treatments and coatings can be used to improve the performance of planted seed seed treatments referred to treating the seed with fungicides or insecticides which help prevent microbial or insect attack on germinating seeds and seedlings this is especially helpful in cool wet soils or where seed germination is delayed in the u.s. hybrid corn seed is usually treated with a fungicide the fungicide on treated corn seed is toxic and has died to prevent possible mixing with seed destined for animal or human use care should be taken when handling treated seed research is also being conducted on seed coatings seed coatings generally refer to a variety of substances used to coat the seed for different purposes encapsulating seeds and pill like coatings can be used to make bigger or more uniform shaped seeds to aid in planting they may help reduce the environmental hazards associated with treated seed by impregnating pesticide chemicals into the coating this approach may reduce toxic dusts and chemical leaching and soil as coating technology advances seed injury resistance seed storability and timing of seed germination in the field may be possible by regulating coating characteristics these advancements may help lower use of toxic seed treatments the next topic for study is the section on seed tests you should now stop the VCR and study this section in your text then return to the VCR for further tutoring different seed quality tests can be conducted to determine the suitability of the seed for planting purposes these tests provide useful information to the grower buyer and seller of seeds one of the most common seed quality tests is the germination test seeds are germinated in warm moist conditions on germination paper sand or in other mediums according to procedures established for each crop species after a specified germination period the number of normal abnormal and hard seeds are counted and the germination and hard seed percentages are calculated this germination test is conducted under ideal conditions thus it estimates the maximum germination potential of the seed germination percentages from the laboratory germination test are often higher than those observed in actual field conditions where conditions are more stressful laboratory vigour tests have been developed to measure germination performance of a seed lot in more stressful conditions a commonly used vigor test for hybrid corn seed is the cold test seeds are placed in moist soil or sand at ten degrees Celsius for about seven days and then allowed to germinate under warm conditions this test was developed to estimate germination performance in cool moist field conditions the accelerated aging test is another vigor test used for many species including soybeans seeds are exposed to high temperatures of over 40 degrees Celsius and nearly 100% relative humidity for three or four days and then allowed to germinate under optimum conditions germination is then observed under these more stressful conditions the tetrazolium test commonly called the t Z test is a different type of seed test that can be used to estimate seed viability this test can be completed in the relatively short time of one or two days moist seeds are placed in a solution containing a colorless tetrazolium dye viable seeds and tissues absorb and change the colorless dye into highly visible reddish colors dead seeds or parts of dead seed tissue do not change color allowing one to readily distinguish living from dead tissues under trained observation the TZ test can be used to estimate the percentage of viable seed in a seed lot purity analysis is another important seed quality test that indicates the purity of the seed sample and its suitability for planting purity analysis is a physical examination and separation of the different components of the seed sample these components are recorded in percentages based on weight and include pure seed other crop seed weed seed and inert matter pure seed as the percentage of seed of the kind submitted for testing thus if a wheat sample is submitted for testing pure seed is the percentage of wheat seed in that sample other crop seed is the percentage of other kinds of crop seeds in the sample weed seed is a percentage of all weed seeds in the sample the names and number of secondary noxious weed seed per unit weight are reported state laws define the noxious weed list and if the more serious primary noxious weed seeds are found in the sample the seed cannot be sold inert matter is the percentage of chaff stones and other non seed materials found in the sample state and federal seed laws require certain test information to be printed on seed labels for each bag of seed sold there are official recognized seed testing laboratories in each state that will conduct the necessary seed test information for labeling a typical seed label usually includes name and address of the grower variety and of seed the seed lot number the percentages by weight of pure seed inert matter other crop seed weed seed noxious weeds the germination and hard seed percentages date of seed testing and net weight of the bagged seed the seed label therefore provides important consumer information for evaluating seed quality for planting the next topic for study is the section on mechanical damage in seeds you should now stop the VCR and study this section in your text then return to the VCR for further tutoring mechanical damage refers to the physical damage of seed from harvesting cleaning and handling sometimes the damage is obvious seeds are split broken or cracked other times small cracks in the seed coat or internal damage occurs that are difficult to visibly detect a sodium hypochlorite test is a quick unofficial test for determining cracked seed coats and mechanical damage in soybean seeds it can be conducted using common household bleach which contains about 5% sodium hypochloride dilute the bleach using one part bleach and four parts water soak 20 or more randomly selected seeds in a container containing the diluted bleach and check for cracked seed coats during the next 10 to 15 minutes seed coats of the cracked soybeans will be swollen and separated from the cotyledons this test can be conducted in the field during combining and helps determine if combine adjustments are necessary to reduce mechanical damage mechanical damage can injure seeds internally which may be detected only by proper laboratory tests thus gently handling seeds during harvesting transporting conditioning and bagging operations are extremely important in maintaining good seed quality a few of the ways to minimize mechanical seed damage are harvesting seed at the right moisture content with properly adjusted harvesting equipment using bucket elevators and rubber belt conveying systems avoiding unnecessary metal on seed contact and preventing large vertical drops of seed the next topic for study is the section on determination of pure live seed you should now stop the VCR and study the section in your text then return to the VCR for further tutoring pure live seed percentage describes the pureness and German ability of a seed lot it is calculated by multiplying the percent purity and percent germination and dividing by 100 pure live seed is very useful to compare the worth of different seed Lots the real cost of seed can be determined by dividing the quoted selling price by the decimal conversion of pure live seed percentage this allows one to compare the real costs between seed lots of different germination and purity percentages remember though pure live seed percentage is not the final word in choosing seed for planting purposes if a seed lot contains seeds of a troublesome weed you may not want to plant it even though it has a very high pure live seed percentage pure live seed calculations also allow farmers to adjust seeding rates for germination and purity differences in various seed Lots for example suppose the recommended planting rate is 5 kilograms of pure live seed per hectare the seed you are planting is 80% pure and has 90% germination which gives a pure live seed percentage of 72 percent dividing the recommended 5 kilograms per hectare planting rate by the decimal conversion of 72 percent gives the actual seeding rate needed to plant 5 kilograms of pure live seed per hectare in this example the planter should be adjusted to plant 6.9 kilograms of seed per hectare to attain the desired seeding rate the next topic for study is the section on increasing seed supplies you should now stop the VCR and study the section in your text and return to the VCR for further tutoring in the past it was difficult to obtain high quality seed of newly developed varieties the distribution of new varieties often was inequitable to growers varieties were mixed with other varieties and the genetic identity was hopelessly lost soon after varietal release the lack of seed quality standards and test procedures made it difficult to determine for from good quality seeds these problems characterized the early years of the seed industry in the u.s. now federal and state seed laws have been established which regulate the sale of seed and require that certain seed quality standards be met regulations apply to seed labeling germination purity weed seed content and other seed quality information state seed certification programs also have been established to maintain quality and provide an organized pathway of seed increase of new varieties to farmers for example let's follow the pathway of certification and seed increase of a new variety of soybeans the soybean breeder who developed the new variety has spent years developing it and now has bushels of genetically pure seed this is called breeders seed this new variety is described in detail to the state's certification agency who will use this information to certify the genetic identity in later generations of seed increase the breeders seed is given to the manager of the state's foundation seed program the breeder seed is carefully grown maintained and certified for genetic purity 60 bushels are harvested it is now called foundation seed the 60 bushels of foundation seed will be distributed to the state's registered seed dealers each registered seed dealer will plant their portion of foundation seed and carefully manage it to meet registered seed certification requirements collectively all 60 bushels of foundation seed will be planted by the registered seed growers if each bushel planted yields 60 bushels harvested and certified then there will be 36 hundred bushels of seed of the new variety it is now called registered seed the 3,600 bushels of registered seed will be distributed among the state's certified seed dealers each certified seed dealer will plant their portion of registered seed and carefully manage it to meet certified seed requirements collectively all 3,600 bushels of registered seed will be planted by the certified seed growers if each bushel planted yields 60 bushels harvested and certified then there will be two hundred sixteen thousand bushels of seed of the new variety it is now called certified seed the two hundred sixteen thousand bushels of certified seed will now be sold and distributed to the public this method of seed increase using a certification agency for each level as an effective orderly procedure to provide growers with genetically pure seed of a new variety this example of seed increase is one used by University and federal plant breeders private seed companies may have their own seed increase and certification procedures but the principles of an organized and effective seed increase program are the same in the u.s. the owner of a new variety may have legal protection from someone who is unauthorized to grow and sell it a sexually propagated crops can be protected through plant patenting procedures established in the 1930s however sexually propagated crops were not protected until the establishment of the plant variety Protection Act in 1970 protected varieties as they are called are legally protected for 17 years and then the variety becomes public property varieties which do not have legal protection are called common varieties both private varieties or those developed by private enterprise and public varieties or those developed by public institutions can be protected the next topic for study is the section on grain quality you should now stop the VCR and study this section in your text and return to the VCR for further tutoring grain quality refers to the market value of the grain either for feed or food purposes unfortunately before the early 1900s in the u.s. grain quality factors were not clearly defined these factors varied according to the particular buyer interested in making a cheap purchase in 1916 the u.s. grain Standards Act was passed which established grain quality standards for different crops this Act provided a uniform means to identify grain quality u.s. number-3 sorghum for example is similar quality whether the grain is in New York New Orleans or des moines by officially determining grain quality through established procedures grain market quotations and buying and selling transactions can take place in the world's trade centers grain pricing in the u.s. is based on us number two grade quality basis grain buyers for domestic and export markets in the Chicago and Kansas City Board's a trade for example become more confident and willing to purchase grain when quality is known grain handling and transportation is also improved because grain can be stored and moved in bulk according to quality buyers of grain often purchase large amounts that can be transported by rail barge or ship a food processing company in Michigan can order a 100 car train load of us number to quality corn in Iowa and be confident that each hopper car on the train is number-two quality the procedures for grading grain are established for each crop an outlined in the u.s. grain standards manual the federal grain Inspection Service is responsible for licensing supervising and regulating grain inspection procedures most grain brought in by farmers is not officially graded in formal inspection by local elevator employees usually occurs to ensure that moisture quality factors such as various grain damages are not severe enough to warrant discounting the price paid to farmers grain quality discounts are not usually imposed unless the quality is below us number two grade standards official grading is commonly needed however when requested by the buyer or if grain is transported in interstate commerce licensed GRA inspectors approved by the federal grain Inspection Service are responsible for officially inspecting and grading grain official grades are often needed as grain is bought and transported from country elevators and major grain terminals at river and coastal locations grading grain to assess the quality as only as good as the sample proper sampling is necessary to obtain an accurate representation of the whole lot automatic sampling devices are used to sample grain throughout the grain mass the sample size taken is approximately 2,000 grams once this sample is taken grain inspection personnel examine and verify the type of grain they look for any evidence of heating presence of live grain insects or grain odors such as musty sour or pesticide odors the sample is divided into smaller portions for further analysis this is done with a sample dividing device such as a burner divider this device is designed to divide the sample without bias so that the true representation of the original sample is maintained of the 2,000 gram sample a file sample of about 1,000 grams is stored for future reference in case the grade is questioned and appealed for reconsideration the remaining 1,000 gram sample is used to determine moisture test weight grain damages and other factors sample sizes for different determinations may range from less than 50 grams to more than 200 grams the grain sample is examined to determine the class of grain class refers to the overall type of grain such as corn hard red winter wheat six Road barley and yellow soybeans some types of grains have subclasses which further describe the grain class and suitability for different purposes for example there are eight classes of wheat three of these classes are divided into subclasses hard red spring wheat is a class that is utilized as a bread wheat it has a subclass called dark northern spring wheat which is extremely desirable to Millers and makers classes and subclasses are determined on varietal and kernel characteristics grain samples are also examined to see if any special great designations apply special grade designations do not influence the numerical grade but are noted on the grain grading ticket and further indicate desirable or undesirable grain characteristics terms such as infested Herget e garlicky smutty and extra-heavy are examples of special grade designations the procedures and requirements for special grade designations vary for different crops dockage is measured for some crops dockage is all material that is readily removed by cleaning operations it is determined by specially designed dockage machines or by hand sips dockage is measured as a percentage of sample weight and noted on the grain grading ticket dockage when applicable indicates how clean the grain is grain moisture is determined by approved and regularly inspected moisture meters moisture percentage does not influence the numerical grade of grain but is noted on the grain grading ticket grain moisture is extremely important to all green users because it influences transportation storage and processing value additional analyses of the grain sample are used to determine grade factors grade factors are those that affect the numerical grade of the grain samples of various sizes are used and many require hand separation and visual inspection for each factor information published in the grain inspection handbooks outline the grade factors for each crop for example the table of grades and grade requirements for maize indicates factors which determine numerical grades ranging from 1 to 5 with 1 being the highest reading and sample grade being the lowest rating these factors include test weight heat damaged kernels total damaged kernels broken corn and foreign material stones glass and other factors there are many types of grain damages that inspectors look for examples of grain damages are heat damaged kernels that may indicate poor storage conditions excessive kernel respiration and spoilage or heat damage from drying grain insect damage kernels sprout damaged kernels whether damaged kernels and diseased kernels are other examples of grain damages after all determinations are made and numerical grades or sample grade factors are assigned to each factor the overall grade of the lot is written the overall grade is the lowest grade of any individual factor for example suppose the numerical grades for individual factors in a sample of sorghum were number one for test weight number two for heat damaged kernels number four for total damaged kernels number three for foreign material and number two for kokin kernels and foreign material the overall grade of the sample will be number four the determining factor is total damaged kernels the overall grade may be written as US number for sorghum determining factor total damaged kernels if the special grade designation of infested was required then the overall grade would be written as US number for sorghum infested determining factor total damaged kernels seed and grain quality are important goals that affect many aspects of agriculture from production and storage to marketing and transportation and to processing and use producing and maintaining high quality are critical components to a sound agricultural system this is the end of the chapter on seed and grain quality you should now be ready to try to self evaluation test at the end of the chapter in your text