6B.1. Construction

The 4-wheel tractor zero-till drill (Plate 6B.1) is similar to the 2-wheel tractor seeder, except that the openers that place the seed in the soil are fixed rather than rotary. Also, this drill is a combination drill and has the ability to place fertilizer as well as to plant small seeded crops like wheat, barley and vetch. There are two bins (Plate 6B.2), the front one for fertilizer and the rear one for seed. The fertilizer and seed tubes are attached to the front and back tubes of the opener (Plate 6B.3), respectively.

The ability of the drill to place the seed and fertilizer improves the efficiency of establishment and fertilizer application over the traditional broadcast system. However, during seeding, the operator must be careful never to allow the drill to move backwards while still inserted in the soil, otherwise the tubes can be blocked with soil that prevents the seed or fertilizer flowing. The operator must lift the drill while moving forward to prevent this blocking problem. The operator should check the tubes at the end of each pass to make sure they are not blocked. Special care is needed when planting small plots for experiments and demonstrations, and it is worth having an assistant employed just to check seed and fertilizer tubes are clear.

Opener spacing and arrangement

The drill can have different opener spacing and arrangements:

1) Depth: to control the depth of the openers (Plate 6B.4) move the shaft of the opener up or down. Use holes on the shaft to make sure that the opener is secure.

2) Spacing: to adjust spacing between rows loosen the brackets shown in Plate 6B.5 and move the openers closer or further apart - assuming there is space for the drive wheel.

3) Arrangement: the drill has six openers that allow seed and/or fertilizer to be placed in the soil. The opener arrangement can have all six openers in one line, or staggered with some openers in the front and others behind. Plate 6B.1 shows 2 openers at the front and 4 openers at the back. There is more chance of loose residue clogging the drill with all six openers in one row. This can be overcome by using the staggered configuration. Note that the openers for the front are of different design compared to those for the back (Plate 6B.6).

Seed and Fertilizer Systems

The seed and fertilizer systems differ mainly in the size of the fluted rollers (Plate 6B.7). The fertilizer flutes are larger than the seed flutes so that sufficient fertilizer can be applied. Plate 6B.8. also shows the mechanism for opening and closing the seed and fertilizer holes. Open the slides during planting, but close them for transport between plots and fields. Open the slides again to remove excess seed and fertilizer, and to clean the bins and seed and fertilizer mechanisms. There is also a black plastic cover shown open in Plate 6B.8 that is held in place with a metal wire clip (Plate 6B.9 and 6B.10). Open this black plastic cover to clean the seed or fertilizer tanks of excess material. The clip shuts the black plastic cover and also holds the green bucket that directs the seed or fertilizer into the tubes.

6B.2. Calibration of seed and fertilizer rates

Both the seed and fertilizer rates need to be calibrated before going to the field. If a new variety or crop is used a new calibration is needed. Calibration is done as follows:

1) Determine the circumference of the drive wheel (Plat 6B.11). The outer circumference is correct. Also check the spacing set for the openers.

2) Make sure that the clip (Plate 6B.10) is in place and the black plastic cover is fully closed and the green bucket in the correct position.

3) Adjust the fertilizer or seed meter (Plate 6B.12) for the test using the wheel on the side of the seeder (Plate 6B.13) - loosen the lock nut and turn the wheel. This wheel slides the seed or fertilizer flutes so that more or less material is dispensed. Use this adjustment to increase or decrease the seed or fertilizer rate until you obtain the correct value. This may take several attempts. Note down the value that is seen on the seed or fertilizer meter for future reference. Tighten locknut after adjustment is finished.

4) Add just sufficient seed or fertilizer for the calibration by placing the material over the openings in the seed or fertilizer bin.

5) Open the metal slide (Plate 6B.10) to the setting that will be used in the field. Opening this slide fully will ensure the maximum flow but it can be partially opened to give an intermediate rate.

6) Place cloth, paper or plastic bags around each tube to collect the seed or fertilizer dispensed. You can calibrate the seed and fertilizer at the same time by placing bags on the 6 seed and 6 fertilizer tubes.

7) Make a mark on the drive wheel or tie a piece of cotton or string in one place on the wheel, so that it is possible to count the number of revolutions.

8) Raise the zero-till drill with the tractor hydraulics and turn the drive wheel by hand 10 full turns. The circumference times 10 will give the length the drill is presumed to have moved.

9) Collect the 6 bags of seed and / or fertilizer from the tubes and note if each has approximately the same quantity. This gives a visual check that the flutes are distributing seed or fertilizer evenly at all 6 openers. Weigh the seed and fertilizer with an accurate balance from the consolidated 6 samples.

Calibration calculations

To determine the area covered when the seed drill moves the length of 10 turns of the drive wheel, multiply the length (10 times the circumference), which for this machine is 15.5 metres, by the width 1.20 metres (6 rows spaced 20 cm apart), which gives an area of 18.60 square metres.

1) In order to get 100 kg seed or fertilizer per hectare, 10 grams of material needs to be dispensed per square metre (100kg x 1000 / 10,000 m²). Therefore the amount of seed or fertilizer in the 6 bags should equal 18.60 times 10 grams or 186.0 grams. Adjust the seed or fertilizer meter in or out to increase or decrease the flow and re-calibrate again. Repeat until the correct value is obtained.

2) Note for fertilizer, the percent of N in urea is 46 and N and P₂O₅ in DAP is 18 and 46% respectively. In order to get the correct quantity of urea or di-ammonium phosphate you need to divide the N or P₂O₅ value wanted to apply by the percent nutrient to get the amount of product. For example:

• To get 100 kg N per hectare divide 100 by 0.46 to get 217 kg of urea or 21.7 grams per square metre.
• For P₂O₅ you first calculate the P₂O₅ value needed and then see how much N is also applied. For example to add 50 kg P₂O₅ divide 50 by 0.46 to get 109 kg/ha DAP or 10.9 grams per square square. This also applies 109 times 0.18 or 19.6 kg N per hectare.

6B.3. Planting

Once the drill is calibrated, fill seed and fertilizer boxes with the appropriate quantity of seed for the area to be planted. Don’t add too much, otherwise the chore of cleaning out the extra seed and fertilizer will be harder. During the planting, the operator or attendant needs to check the seed and fertilizer boxes to make sure there is sufficient material available over each hole so that missing lines do not occur.

Adjust the pressure of the press wheel (Plate 6B.14) to have the slot made by the opener properly pressed to ensure good seed and soil contact. To adjust the pressure, remove the clip at the top of the spring assembly, tighten the spring, and replace the clip in a lower hole.

The speed with which the tractor moves does not affect the seed rate. If the tractor moves faster, the seed flows faster but applies the same seed or fertilizer per hectare. During the first pass of the tractor check the depth of seeding and fertilizer placement, and adjust as necessary. Make sure that when the end of a pass of the tractor is reached, the seed drill is raised while still moving forward and before the tractor stops. This is to prevent seed and fertilizer dropping and clogging of the tubes. At the end of each row have a person check that the tubes are clear and that the seed and fertilizer are dropping properly.

6B.4. Maintenance of the Zero-Till Drill

Always carry out the following maintenance before and/or after use as appropriate

Before Use

1) Never mix DAP and urea together unless you intend to use immediately. These two compounds tend to deliquesce and form a solid mass if left too long. That will then require a lot of effort to clean the fertilizer box.

2) Maintain the proper chain tension on the drive chain (Plate 6B.11) using the adjustor, and check the chain fits the sprockets properly and that the sprockets are not worn. Replace sprockets and chain if needed.

3) Oil and grease all moving parts, especially bearings and sprockets.  If grease nipples are not fitted for bearings, carefully remove bearing caps (without dropping them in the dirt!), pack the bearings with grease, and replace the bearing caps securely.

4) Replace broken parts from a stock of spare parts kept at the workshop. Replace parts as they break - do not wait until the whole machine does not work!

5) Tighten all nuts and bolts each morning before use, and after breaks - to make sure they don’t come loose and get lost. Make sure that the openers are held tightly and straight. Use a set of spanners that fit the nuts and bolts of the machine - continual use of pliers will round the nuts so that spanners cannot grip them.

6) Make sure the tubes are properly fixed so that they do not come loose during operation. Check before use that tubes are not blocked, and re-check frequently during use. Fit clear plastic tubes so that seed and fertilizer can be seen moving through them during work.

After use

1) Always clean out excess seed from the “seed box” immediately after use. It will pick up moisture and start to germinate or go mouldy, and form a solid mass. This can be done by removing the clip that holds the black plastic cover and green cup and pulling the slide out fully (Plate 6B.10).

2) In trial work it is essential that all seeds are cleaned out between plots. Use a soft brush and pan to collect seeds. An easy way is to use a small vacuum cleaner designed for cleaning cars, worked off a 12 volt car battery.

3) Always clean out excess fertilizer from the Fertilizer box immediately after use. This can be done by removing the clip that holds the black plastic cover and green cup and pulling the slide out fully (Plate 6B.10). Never leave fertilizer in the fertilizer box. It will cake solid and rapidly corrode the metal of the box and metal parts of the metering system.

4) Wash out the last traces of fertilizer with boiling water, and use an old tooth brush to remove fertilizer caked on to fertilizer flutes, fertilizer slides, around openings from the fertilizer box, and inside the fertilizer cup. Wash out the plastic fertilizer tubes, and remove fertilizer from the fertilizer openers. Make sure all parts are dry before using again.

Plates