It was observed in both the greenhouse and field that
lettuce and carrots may be established by planting single
seeds in holes punched through the soil crust. When the
holes are not back-filled, seeds planted as deep as 60 mm
will produce healthy plants in a few days. Preliminary
experiments indicate that in some climatic regions a practical
field management system could be developed which
will eliminate emergence problems arising from soil crusting
and premature drying of shallow seedbeds. The open
hole punch method may also prove useful in controlling
the temperature and salinity adjacent to the seed and in
reducing initial tillage and irrigation requirements

Cary, J.W.

USDA - ARS - NWISRL

ABSTRACTIt was observed in both the greenhouse and field thatlettuce and carrots may be established by planting singleseeds in. holes punched through the soil crust. When theholes are not back-fined, seeds planted as deep as 60 mmwill produce healthy plants in a few days. Preliminaryexperiments indicate that in some climatic regions a prac-tical field management system could be developed whichwill eliminate emergence problems arising from soil crust-ing and premature drying of shallow seedbeds. The openhole punch method may also prove useful in controllingthe temperature and salinity adjacent to the seed and inreducing initial tillage and irrigation requirements.Additional index words: soil crust, soil moisture, seed-bed, salinity, soil temperature, minimum tillage.BECAUSE lettuce and carrot seeds are small and producephysically weak seedlings, it is not always easy toestablish a stand in the field. Since these seeds are ordin-arily planted only a few millimeters deep, they are subjectto desiccation before a root system can be established.Moreover, the germinating seedlings may experience greatdifficulty in penetrating even a mild soil surface crust.Arndt (1965a, 1965b) has published two papers inwhich he has reviewed the present knowledge of soil crust-ing in addition to presenting significant new material con-cerning the mechanics of seedling emergence through acrust. Even so, the statement made by Petezval and Lutz(1957) still sums up the situation, i.e., "Different soilsrespond differently to the environmental conditions to whichthey are subjected. The hardness of the crust on any partic-'Contribution from the Northwest Branch, Soil and WaterConservation Research Division, Agricultural Research Service,USDA; Idaho Agricultural Experiment Station cooperating. Re-ceived March 1, 1967.'Research Soil Scientist, Snake River Conservation ResearchCenter, Kimberly, Idaho.Purchased by Agricultural Research Service,U. S. Department of Agriculture, for official use.Reprinted from the Akaoxolly JOURNALVol. 59:406-408, 1967.Punch Planting to Establish Lettuce and Carrots Under Adverse Conditions'J. W. Caryular soil is a result of the complex physical and physical-chemical processes or reactions which are controlled by theproportions and nature of the soil components and by ex-ternal conditions." While a soil crust may stop seedlingemergence by limiting oxygen diffusion or by becoming toodry, the harm generally results from a mechanical impe-dance. For example, Hanks and Thorp (1956) found thatthe oxygen diffusion rate had to drop below 10- 6g/cm2 imin before seedlings were affected and Doneen andMacGillivray (1943) showed that most vegetable seedsgerminated well so long as the soil moisture content doesnot drop below the permanent wilting point. In general,it is not that seedlings cannot develop enough force tobreak through a crust but rather that the horizontal seedbedconstrains are not sufficient to direct the pressures from thegrowing seedling upward. Gill and Bolt (1955) have saidthat the average axial pressure developed by germinatinggrass seedlings is around 7.5 bars, which, for a growingpoint with a 2 mm2 tip, is enough to break through anyof the crusts studied by Arndt (1965). This was recog-nized by Carnes (1934) when he recommended packing thesoil to provide a firm foundation for seedling pressure todevelop upward against the surface crust. The use of soilconditioners and surface mulches has been studied as possi-ble alternative solutions. While Bennett et al. (1964)found that soil conditioners could increase emergence froma normal 10% up to around 50% on some soils, the prac-tice is still not entirely satisfactory.The concept of a firm seedbed and the beneficial effectsfrom soil conditioners and mulching, combined with laborshortages and costs have resulted in an effort to developmachinery that will plant single seeds in holes punched atdesired intervals along the row. However, one unansweredquestion in this type of planting system is: What should theseed ,be covered with so that a high percentage of emer-gence will be assured? It has been noted at this Centertoil crustSW in normal badSoul in openligl b AGRONOMY JOURNAL, VOL. 59, SEPTEMBER–OCTOBER 1967that the lettuce and carrot seeds, among others, will de-velop normally and produce healthy plants when the holeis not backfilled at all, providing the hole has a satisfactorydiameter-to-depth ratio. Lettuce and carrot seeds containsufficient energy to grow 40 to 80 mm high without energyfrom photosynthesis. Thus, it seemed possible that theseseeds could be planted in holes 60 mm deep with a reason-able chance for emergence.EXPERIMENTAL PROCEDUREA box with the sides 0.70 X 1.80 m and 0.35 m deer, wasplaced on the greenhouse bench. It was packed with Portneuf siltloam soil and several crops were grown before beginning the ex-periments reported here. Since the study was carried out in thewinter, a bank of lights (800 watts) with aluminum reflectorswas mounted over the box to provide additional radiation energyto the soil surface. These lights burned continuously from 5:00AM to 8:00 PM. An 8-inch fan was available for blowing air acrossthe soil surface to increase the drying capacity of the microcli-mate. The evaporation from a free water surface was 18 mmper day under these conditions and 9 mm per day when the fanwas not used.'The box was divided into four sections, each section containinga replicate in which 20 seeds per row were planted. The followingfive experiments were carried out:1. The soil surface was shaped as shown in Fig. is and sprinkledwith water. As . saon as the soil was dry on top, holes 60 mmdeep were punched through the crust along the peak of the ridgewith a tapered rod. The rod diameter was 5 mm at the bottom and9 mm at the top. A single seed was dropped in each hole. Theseeds were not covered with any material. As shown in the dia-gram, the crust was broken up on the other side of the irrigationfurrow and worked into a suitable seedbed. Twenty lettuce seedswere then planted in the conventional manner and firmly coveredwith 5 to 10 mm of moist soil. This will hereafter be referred toas the "normal" method of planting, The irrigation furrow wasfilled with water once each day so that the surface of the normallyplanted row remained moist and did not crust over. The surfaceof the punch-planted ridge remained dry and crusted. The fan wasnot used.2. The planting arrangement was the same as described in Treat-ment 1. Immediately following planting, the surface was sprinkledwith 12 to 18 mm of water in about 20 min. The spray was of finedroplets and soil conductivity was such that excessive washing anderosion did not occur. The soil received no further application ofwater. The fan was not used after the first 24 hours required todry the soil surface.'This was measured in a tube filled with water which wasburied in the soil so that its top was level with the surface. Thetube had a 5-cm inside diameter and was 20 cm deep.Fig. 1. A cross-sectional diagram of seed placements in the green-house emergence trials.3. The shaping and planting procedures were the same as de-scribed in Treatment 2, but immediately after planting the surfacewas lightly sprinkled with approximately 3 mm of water, justenough to moisten the surface. The furrows were filled with wateronce a day. The treatment differed from No. 1 in that the fanwas allowed to run continuously, increasing the drying rate atthe surface so that a crust did form over the normally plantedrow. Because of the fan, this row did not sub up enough so thatthe surface became moist following the irrigations.4. The soil was leveled, smoothed, and flooded with water andthen allowed to dry on the surface. As soon as the soil was dryon top, a normal planting was made by breaking up the crust,forming a moist seedbed wide enough for single rows. Plantingsin holes 20, 40, and 60 mm deep were made by laying individualseeds on the surface crust and punching them down with the probepreviously described. The planting arrangement is diagrammed inFig. lb, No water was added after planting, This treatment wascarried out using both carrot and lettuce seeds.5. This treament was the same as No. 4 except that the surfacewas sprifitkled with 10 mm of water in a fine "nonerosive spray"immediately after planting.Soil and air temperatures were measured intermittently through-out the daylight period with thermocouples. Notes were made ofvisual observations of the germination and emergence processes,but the most interesting data were counts of the seedlings whichhad emerged approximately 10 days after planting.RESULTSThe number of plants which emerged out of the 20 seedsplanted in each row are shown in Table 1. for each of thefive treatments. Typical afternoon soil surface temperaturesare also shown in this table.In Treatment 1, which provided nearly optimum growingconditions for the normal method of planting, normallyplanted seeds appeared to give slightly better results thanthe seeds that were dropped into the 60-mm holes, Tendays after planting date, the seedlings from normal-plantedrows appeared larger and more vigorous than those plantedin holes. While germination times appeared to be quitesimilar, the seedlings in holes required several extra daysto reach the surface and so were farther behind in photo-synthesis.In Treatment 2, the normal planting did not yield anyseedlings. It appeared that the principal problem wascaused by the seedbed drying out before the seed couldgerminate. Those that did germinate were unable to pene-trate the crust. Sprinkling the soil surface following plant-ing did not reduce germination or emergence from the holesas much as one might have thought. While some soil didwash in on top of the seeds, drying of this soil was veryslow since it was still several centimeters below the surface.Consequently, the seedling emerged through the coveringsoil before it hardened. In cases where the soil washed into cover the seeds with a 3- or 4-cm thick layer, the chancesof seedling emergence were slight.Table r. Observations of seedling emergence under various envi-ronmental conditions in the greenhouse. Treatments are de-scribed in the text.Number of plants emerging from 20 seed rowsTreat- 	nit	 Normal	 60-mm	 40-mm	 209ran1.etteiett,_1 17 16 20 15 14 15 15 15 -- •-• 302 0 0 0 0 12 8 9 11. 273 7 1 0 3 16 17 12 17 -- -- 204 0 0 0 a .9 4 2 4 13 10 1 10 13 11 10 11 94Carrotsta 0 0 0 0 10 6 4 6 3 2 0 1 0 0 0 1 946 0 0 0 1 11 7 10 12 13 9 a 16 1 2 2 2 33• Representative daytime surface temperatures. i Great lakes variety, 01%guaranteed germination. 	 1 Hants!! Coeless variety, 00% guaranteed germination.Temp.CARY: PUNCH PLANTING OF LETTUCE AND CARROTSFig. 3. Beans which grew from seeds dropped in holes 15 to 25cm deep.appeared to do especially well planted 15 to 25 cm deepin holes 2 cm in diameter. Some of these plants are shownin Fig. 3. The foremost row grew from seeds planted 20cm deep.Fig. 2. Carrot seedlings emerging from 40-mm deep holes duringTreatment 5. Note the poor physical condition of the soil fornormal seedling emergence.The poor results of seedling development under normalplanting in Treatment 3 were due primarily to the crustwhich formed on the surface. Many of the seeds were ableto germinate as the moisture subbed up daily into theirseedbed from the irrigation furrow, but the seedlings didnot have the physical strength to break through the 3- or4-mm crust which had formed over them.In Treatment 4, the failure of the normal plantingappeared to be primarily caused by the seedbed drying outbefore the seeds could germinate and establish a rootsystem. Ten days after planting, the soil was dry to a depthof 6 to 8 cm.Treatment 5 produced better carrot stands than No. 4because the water added immediately after planting causedthe soil to remain moist in the 20- to 40-mm zone longenough for some germination to occur. Carrot seedlingsemerging from the 40-mm holes are shown in Fig. 2.This photograph shows the poor conditions of the soil fornormal seedling emergence.In addition to the elimination of the crusting problemand the promotion of better seedbed moisture conditions,the punch planting method also had a beneficial tempera-ture effect on the lettuce seeds. The temperature was 2 or3 C less in the 60-mm deep hole than was the temperaturearound the normally planted seeds. This is an importantconsideration in some areas of the Southwest where irriga-tion is required for cooling.In addition to the greenhouse experiment, preliminaryplantings were made in the field during April and May1966. During this period, evaporation from a WeatherBureau pan rose from 7 mm per day to 9 mm per day. Themean air temperatures rose from 8 to 18 C. Holes of vari-ous diameters and depths were punched through the soilcrust and a variety of seeds dropped into them. The seedswere not covered other than with what dust might fall infrom the surface, Carrots, lettuce, sweet corn, sugar beets,cabbage, potatoes, and beans all produced plants from seedsplanted in this manner, provided there was moist soil atthe bottom of the hole at the time of planting and providedthe hole was not filled in before seeding emergence. BeansCONCLUSIONSThe punch planting method allows seeds to be placedmuch deeper in the soil than the conventional practice ofcovering them in a seedbed. Problems of crusting and pre-mature seedbed desiccation may be significantly reduced bythe punch method, particularly for weak seedlings such aslettuce and carrots. It offers a practical method for con-trolling both the seed's temperature and the depth of soilwhere rooting occurs, particularly for plants such as cornand beans, which can be planted 15 to 25 cm deep. Themethod may also prove useful in conservation of irrigationwater early in the season and in promoting a minimumtillage program. The author feels that punch plantingwithout backfilling the holes has immediate practical appli-cation in areas where a stable soil crust can be formed andwhere heavy, erosive rains are not apt to occur during thegermination and emergence period.ACKNOWLEDGEMENTThe author appreciates the stimulation from several discussionswhich developed during the Western Regional W-66 committeemeetings, and in particular those lead by Dr. Paul Day.LITERATURE CITED1. ARNDT, W. 1965a, The nature of the mechanical impedanceto seedlings by soil surface seals. Aust. J. of Soil Res, 3:45-54,2. 	 . 1965b. The impedance of soil seals and theforces of emerging seedlings. Aust. J. of Soil Res. 3:55-68.3. BENNET, O. L., D. A. ASHLEY, and B. D. Doss. 1964. Meth-ods of reducing soil crusting to increase cotton seedling emer-gence. Agron. J. 56(2):162-165.4, CARNES, A. 1934. Soil crusts, methods of study, their strengthand method of overcoming their injury to cotton stand. Agric.Eng. 15:167-171.5. DONEEN, L. D., and 3. H. MACGILLIVRAY. 1943. Germination(emergence) of vegetable seed as affected by different soilmoisture conditions. Plant Physiol. 18:524-529.6. GILL, W. R., and G. H. BOLT, 1955. 'Pfeffer's studies of theroot rowth pressures exerted by plants. Agron. J. 47:166-168.7. HANics, R. J. and F. C. Timm). 1956. Seedling emergence ofwheat as related to soil moisture content, bulk density, oxygendiffusion rate and crust strength. Soil Sci, Soc. Am. Proc. 20:307-310.8. PETEZVAL, L., and J. F. LUTZ, 1957, soil crusting and somefactors affecting it. Soil Sci. Soc. Am. Proc. 21:485-491.

Punch Planting to Establish Lettuce and Carrots Under Adverse Conditions

Northwest Irrigation & Soils Research Laboratory Publications

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Punch Planting to Establish Lettuce and Carrots Under Adverse Conditions

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