Grain Drills And Planters - Home NRCS

United States Department of AgricultureNatural Resources Conservation ServiceTechnical Note No: TX-PM-16-03June 2016Grain Drills and PlantersPlant Materials Technical NoteBackgroundGrain drills and seed planters are key components in developing successful conservationplantings. They are complex machines that deliver seed at a metered rate, place it at a consistentdepth in the soil, and produce light compaction to provide good seed to soil contact. Planters anddrills come in many different forms with varying strength and weaknesses depending on the seedbeing used and condition of the planting site. Some require prepared seed beds, others requirelittle to no seed bed preparation, and others are capable of preparing the seed bed and planting inNRCSTechnical Note: TX-PM-16-031

a single pass. Understanding the basic operation of these machines and their strengths andweaknesses is critical in determining which planter is best suited to meet the desired goals of theplanting, or getting the best performance from the available planter.PurposeThis is a continuation of a series of technical notes aimed at assisting conservation planners indeveloping successful conservation plantings. It complements previous tech notes on properseed bed preparation (TX-PM-10-07), planter calibration (TX-PM-10-04), sprayer calibration(TX-PM-11-05), management of conservation plantings (TX-PM-10-03, calculating seedingrates (TX-PM-12-02), and legume seed inoculation (TX-PM-15-01). The purpose of thistechnical note is to provide information on the basic operations of grain drills, the types of drillscurrently available, and the strength and weaknesses of each design.Basic Design and Operation of a Grain Drill and PlantersGrain drills and planters, regardless of type, operate inthe same basic fashion. Seed is held in a box while amechanism driven by the ground wheels or disks dropsseed at a metered rate. Seed falls to the soil surfacewhere some form of compaction seals it in the ground.Seed boxes come in three configurations, standard,legume, and native grass (fluffy) seed. Each box isdesigned to handle specific seed and can usually becalibrated independently of one another. This attributeis very helpful when planting mixes of seed to achievethe desired rate of each species.Standard seed boxes are designed tohandle large smooth seed similar tocorn, soybeans, peas, wheat, oats, etc.They may or may not have agitation tokeep seed moving. They generallyrely on the smooth nature of the seedand gravity to feed the plantingmechanism. These seed boxes willnot handle light, fluffy seed. Seed willbridge on itself and not feed properly;clogging the planter. It is also difficultto calibrate with tiny seed such asclovers. Small seeded species requirea smaller delivery mechanism toachieve the correct planting rates.Seed is typically delivered from theNRCSTechnical Note: TX-PM-16-03Side view of a no-till drill with a 3 seed boxconfiguration for legumes, native grass, and standardseed. Note the size difference of the legume seedbox, first box on left.The inside of a standard seed box showing the gravity fed mechanism thatdelivers seed to drop tubes. Seed is metered out via rollers with gear liketeeth in the openings that control the rate seed flows to the drop tubes.2

seed box through drop tubes to a set of disc shaped “V” openers where it falls into a slice in thesoil left by the openers before being covered and sealed with some form of compaction device.The legume box is designed to handle extremely smallseed, and is much smaller in size than the standardseed box. Operation is generally the same and relieson gravity to feed the mechanism delivering seed tothe drop tubes. The drop tubes deliver seed to theground surface just in front of a compaction devicesuch as press wheels or a cultipacker. Seed is plantedshallower than seed from the standard seed box. Largeseed can jam the smaller delivery mechanism of thelegume box and should not be used.The native, or fluffy seed box is similarto the standard seed box, but has someform of aggressive agitation within thebox to keep seed moving so it doesn’tbridge on itself. Many will have a“pick” wheel mechanism that reaches upinto the seed box and pulls seed downinto the machine to deliver it to the droptubes. The drop tubes are much largerin diameter to help prevent seed frombridging. Removing the fluffy awns andappendages of native grass seed, aprocess called debearding, will greatlyreduce seed bridging in the seed box anddrop tubes. The use of a dry seedlubricant such as powdered graphite isalso recommended to aid seed flow.The smaller seed delivery mechanism of a legumeseed box on a no-till drill. Large seed will jam thesmall gears that deliver seed to the drop tubes.Agitation augerPick WheelClose up view of the agitation auger and the pick wheel inside a nativeseed box. The gear like teeth on the pick wheel reaches into the seedbox, grabs seed, and pull it down into the drop tubes at a steady raterather than relying on gravity to feed the mechanism. The auger bladesmove seed back and forth to keep it constantly moving and prevents seedfrom bridging on itself.Standard Grain DrillStandard grain drills are typically the most common plantersavailable. These planters place seed in narrow rowsapproximately 6 to 8 inches apart. They are most commonlyused for seeding pastures and planting cereal grain crops suchas wheat, oats, and rye. These machines most often use a pairof discs called “V” openers to slice the soil, creating a shallowfurrow for the seed to be placed. Press wheels follow thisaction and use light compaction to seal the opening created bythe “V” openers. Press wheels are spring loaded to allowNRCSTechnical Note: TX-PM-16-03A grain drill with a standard seed box,note the V openers and press wheelswith no fluted coulter.3

adjustment of down pressure based on the soil conditions. They require a prepared seed bed forproper operation. This would include some form of tillage to break the ground, smoothing tobreak up large clods and clumps of soil, and dragging or cultipacking to create a firm seed bed.Because they require prepared seed beds, they may not meet the needs and goals of soil healthand conservation plantings where minimal soil disturbance is desired.No-Till DrillsNo-till drills operate in a similar fashion tostandard grain drills, and also place seed innarrow rows. Seed from the standard andnative seed boxes are delivered to anopening created by “V” openers and sealedwith a set of adjustable press wheels. Themajor difference between No-till drills andstandard grain drills is they do not require aprepared seed bed. Planting sites should bemowed and or treated with a broadspectrum herbicide before planting toreduce competition. They also differ byhaving a fluted, straight disc or coulter thatslices through the unprepared seed bedcreating a cut for the “V” openers to followand open for seed placement. Theseplanters are typically much heavier inconstruction than standard grain drills. Theextra weight helps them break throughexisting plant residue, sod, or hard soilcrust. They may require a larger tractor topull and lift. Because they create virtuallyno soil disturbance, they are favored for soilhealth and conservation plantings whereminimal change to the soil structure isdesired. This minimal disturbance to thesoil also reduces weed competition fromearly successional annual species that areset free by soil disturbances during typicalseed bed preparation such as disking.Planting depth can be difficult to controlwith some no-till drills, especially withsmall seeded species because of theplanter’s increased weight and the openingcreated by the fluted cutting disc. ThisNRCSTechnical Note: TX-PM-16-03Front view of a no-till drill showing the rubber drive wheel, center.This planter has an optional research plot option attached to the top;not typical of standard drills used in conservation plantings.The front fluted coulter of a no-till drill slices an opening through hardsods for the “V” openers, seen middle, to open and deposit seed. Thespring loaded press wheels then seal the opening.4

problem is compounded if the planter’s drive mechanism is driven by the V-openers or flutedcoulter disk. In order for this mechanism to operate consistently, it has to have firm contact withthe soil, sometimes cutting too deep for small seeded species. No-till drills that operate theirdrive mechanism via rubber ground wheels with adjustable height reduce, but don’t eliminatethis problem. Depth bands on the coulter and or “V” openers also help reduce planting depthproblems.Specialty Drills and PlantersDrop SeedersDrop seeders are similar to standard grain drills,but do not plant in neatly spaced rows or use “V”openers. These planters drop seed along the fulllength of the seeding box where it then fallsrandomly between a set of cultipackers and ispressed into the ground. Rolling cultipackers areused to drive the planter mechanism. They workA typical drop seeder with two sets of cultipackers. Seedwell on prepared seed beds, and are capable offalls from the seed box between these rolling cultipackerssmoothing, planting, and cultipacking in a singleduring planting. These are typically used with small seed.pass; reducing some of the site preparation stepsassociated with a standard grain drill. They are also used to over seed small seeded species suchas clover in existing pasture grasses. They handle small seed such as legumes and hard seededgrasses like Bermudagrass very well, and eliminate the issue of planting small seeds too deeply.They will not plant large seeded species deep enough to insure a reliable stand. They are rarelyequipped with native seed boxes, unless specifically ordered.Food Plot and All in One PlantersEver changing improvements in land managementfor wildlife have created new hybrid types ofplanters that combine attributes of the seed bedprepping implements, grain drills, and drop seedersin one machine. They typically have a tillagedevice in front of a seed box that drops seed on thetilled seed bed in front of a set of cultipackers.They are capable of preparing the seed bed,planting, and cultipacking in a single pass;An all in one planter with 3 seed box configuration. Thefront disks prep the seed bed. Seed falls to the groundreducing time spent in the field and fuel used.behind the disks, and the rear cultipackers seal it. Note theThey often come with a standard and legume seedpaint missing on the fluted disk indicating the shallow soildisturbance of this planter. The angle of attack on the disksbox, and some brands have native seed boxesis adjustable vie the orange handle to increase or decreaseavailable upon request. Some models have shortthe soil disturbance.drop tubes which can be moved to multiplelocations to help with planting depth. Large seed can be set to fall directly behind the tillagedevice, while small seed can be delivered between the cultipackers for a shallower plantingNRCSTechnical Note: TX-PM-16-035