Annals of the Missouri Botanical Garden 40: 51-62 (1953)


In January and February of 1935, Professor R. A. Emerson, of Cornell University, and Mr. J. 14. Kempton, then of the U. S. Department of Agriculture, studied maize farming among the Maya Indians at the request of the Carnegie Institution. The following report, circulated in mimeographed form under Dr. Emerson's name, is one of the tangible results of this preliminary survey. Though it has been cited in at least two bibliographies its very existence has been unsuspected by many students of maize. We are indebted to Mrs. Ida K. Langman, of the Academy of Natural Sciences of Philadelphia, for supplying us with a copy, and to Dr. H. E. D. Pollock, of the Department of Archaeology of the Carnegie Institution, for granting permission to reprint the document.

Up until the time of his death Dr. Emerson was the heart and center of research in maize genetics. He was not only the outstanding authority; most of the other workers had either been trained under him or had been closely associated with the work of his laboratory. Mr. Kempton, on his part, has been identified with much of the research on maize which was carried on in the U. S. Department of Agriculture and had taken the lead in studying maize and its relatives in Latin America.

During the last decade, Mexico, in general, and Mexico's pattern of growing maize, in particular, have changed at an ever-accelerating rate. Dr. Emerson's report, though preliminary and informal, gives us an over-all picture of maize in an out-of-the-way part of Mexico fifteen years ago as seen through the eyes of the greatest maize scholar of his time.—EDGAR ANDERSON.


In the course of archeological studies of the ancient Maya civilization, conducted by the Carnegie Institution of Washington and other agencies, it has become important to estimate the density of population that could have been maintained by the agricultural system then in use. Is it possible that the Mayas of one or two thousand years ago could have used a more intensive type of agriculture than that employed by Mayas of the present day? Could the fact that large cities and their contributing territories were abandoned, some of them to be rehabilitated only after some hundreds of years, have been duo even in part to the inadequacy of the agriculture of these regions? Could a possible decline in the productivity of the agricultural land have necessitated abandonment after a century or more? Was such postulated decline in soil fertility related casually to the system of agriculture in vogue?

It was not so much to find conclusive answers to such questions as these as it was to form an opinion of the possible value of a more thorough and sustained agronomic study as an aid in answering them that a preliminary survey of parts of the former Maya region was undertaken.


The survey was conducted under the auspices of the Division of Historical Research of the Carnegie Institution of Washington and under the tutelage of Dr. S. G. Morley of the Chichen Itza project of that Institution. It was begun the latter part of January and continued to the end of February, 1935. The personnel consisted of Mr. J. H. Kempton of the United States Department of Agriculture, and of the writer. Throughout the study they had the help of an interpreter and usually of a local milpero.

The study of milpas was begun at Piste in the central part of the state of Yucatan near Chichen Itza and about 120 kilometers from Merida. Trips between Merida and Chichen Itza by automobile and by train over different routes, a trip by train from Merida southeast to Peto about 150 kilometers, and another by train from Merida southwest to Campeche about 180 kilometers, afforded glimpses of the western half of the state of Yucatan and the northwestern part of the state of Campeche. From a number of places along these lines of railroad, milpas at distances ranging from a few up to 40 kilometers were visited by automobile, tramcar, mule cart, on horse-back, or afoot. Such points of departure were: Piste, Oxkutzkab, and Peto in the state of Yucatan, and Campeche in the state of Campeche.


Topography.—The parts of Yucatan and of Campeche that were visited, as is said to be true of all of the northern part of the Yucatan peninsula, are a low, slightly undulating plain, broken in the southwestern part by ranges of low hills themselves only a few hundred feet above sea level. There is not even a suggestion of a river or brook in all that part of the peninsula visited.

Limestone rock.—The soil is underlaid throughout by a rather soft and porous limestone. Everywhere there appear outcrops of this rock. The sides and tops of small low knolls, often seen to be all rock, and the intervening areas, only a few meters less elevated than the knolls, exhibit many outcrops of rocks. In fact, it is never far from the surface to stratified rock. Although this soft limestone seems to harden on exposure after being taken from quarries, there are abundant evidences of its weathering to produce the usually scant soil. Everywhere exposed rocks are pitted with holes from the size of pin-heads to a meter across and half that deep. Both vertical and horizontal crevices of variable sizes are to be noted greater or less distances apart. Such crevices extend downward for considerable distances, perhaps even to the permanent water table which lies from a few to 50 or more meters below the surface, the distance apparently depending on the relative elevation of the surface. Numerous caves and even large caverns exist. Not infrequently these extend down to or considerably below the water table. When such caverns are open to the surface, they constitute the natural wells, cenotes, of the region, upon which the Mayas depend for their water supply.

Soils.—Evidences of the weathering of limestone rocks to produce soil are so universal that one is inclined to speculate on what would have been the nature of the land surface, had these rocks been exposed for ages to the alternate freezing and thawing in latitudes far to the north. Presumably the low plain would have been covered with some meters of fine loam instead of the scant soil covering now seen. And this might have resulted in a very different type of agriculture from that now prevailing.

On the numerous low knolls the soil is seldom more than a few centimeters deep and on many of them soil is seen only in pockets, or crevices in the rock. Crevices seem to be filled with surface soil and humus to considerable depths, as can be readily observed in recently worked stone quarries. Between the knolls the soil may be a half meter in depth, in some places more, and in many places much less than that. The only relatively deep soils observed are those bordering the ranges of low hills in the southwestern part of the area visited. At Oxkutzkab such border soils were said to be as much as five meters deep. The near absence of surface stone and the luxuriant growth and productivity of citrus trees in this region make such an estimate seem not unreasonable. Evidently the heaviest rains have carried down to the plain enough sediment to build up a relatively deep soil at the foot of the hills. Yet, there is little evidence of even temporary waterways on the hillsides and no evidence whatever of brooks paralleling the base of the hills or leading away from them. The water presumably spreads out in a thin sheet over the plain, depositing much of its sediment before disappearing into rock crevices. These bands of deeper soil at the base of the hills are of very minor importance for the region as a whole, for they are seldom as much as a kilometer wide and in many places are very narrow.

The surface soil, to a depth of a few centimeters on land on which the bush has been undisturbed for from ten to twenty years, is made up largely of decaying vegetable matter. During the dry winter season there is a sparse covering of dry leaves, nowhere the heavy covering seen in northern forests. Beneath this layer of leaves is a shallow layer of partly decayed vegetable matter and below that the red or brown loam. Evidently the relatively high temperature and considerable moisture of the region induce such rapid decay of the fallen leaves that no deep layer of decaying vegetable matter ever accumulates.

Climate.—The entire peninsula of Yucatan lies within the tropics, the northernmost part being somewhat below the 22nd parallel of latitude. The rainfall is light in the extreme northern and northwestern parts of the peninsula. Near Merida and along the gulf coast as far south as Campeche, the annual rainfall is said to be not over 18 to 20 inches. At Chichen Itza the annual precipitation approaches 50 inches. The year is divided into two seasons, a summer rainy season of about five months, usually from May to September inclusive but sometimes beginning nearly a month earlier or a month later, and a dry winter season of about seven months from October to April inclusive.

Some of the weather records kept at Chichen Itza for the past nine or ten years were examined. The total precipitation for 1933 was 50.1 inches and for 1934, 46.6 inches. During the five months, May to September, of 1933, 86 per cent of the year's rain fell; during the same months of 1934, only 73 per cent of the annual rainfall was recorded. Of the 730 days of the two-year period, rain fell on 275 days, 185 of them in the two five-month summer seasons. The maximum rainfall for one day, 4.75 inches, occurred in September, 1933. One-half inch or more of rain fell on 56 of the 275 rainy days, and 46 of the 56 were in the May—September periods. During the two-year period there were 168 days on which .2 inches or less of rain fell, 102 of them having been in the five-month summer seasons.

The mean of the maximum daily temperatures for the years 1933 and 1934 at Chichen Itza was 91.6° F., and the mean of the daily minimum temperatures was 65.6° F. The highest temperatures occurred in March, April, and early May, maximum temperatures of 1010, 103° and 105° F. respectively having been recorded for these months in 1933. When the rainy season begins the maximum temperatures are not as high. Minimum temperatures are lowest during the period from late November to early March. During 1933 the lowest temperature recorded was 47° F., which occurred twice in December; in 1934, 44° was recorded twice in March, and 43° once in December. The lowest temperature on record was 40° F. on January 27, 1935.

Vegetation.—Except for land in crops, the whole of the northwestern part of the Yucatan peninsula is covered by "bush". This consists for the most part of trees and of vines which cling to the trees. In land not in crops for ten to twenty years, the dominant trees are 10 to 15 meters high and 10 to 20 centimeters in diameter. Under these are many smaller trees that have died or been suppressed by the shade of the larger trees. Relatively few annual weeds and almost no grasses are seen in any heavy bush. Both of these occur, however, along trails and in the more open places in the bush.

In bush of only a few years' growth, many annual weeds and small vines are to be seen. Among these are amaranths, numerous composites, and several kinds of bindweed. As the trees grow and shade the ground more and more, these weeds are less and less common. Even in very recently abandoned milpas little grass is seen except in the extreme northern and western parts of the area visited. Here the many large henequen haciendas, in which the bush has been kept cut for ten to fifteen years, apparently return to bush less rapidly when abandoned and more grass is seen.

The surface outcrop of rock does not seem to interfere much with tree growth. It is not uncommon to see large trees with roots exposed on the rock surface for several meters. Evidently the roots grow out in the thin cover of soil until a crevice is reached, then turn abruptly downward. In rock quarries roots 5 centimeters in diameter have been found 2-3 meters beneath the land surface.


Location of milpas.—Difficulty was experienced in learning why a Maya Indian selects a particular site for his milpa. The Mexican Government, in some regions at least, has assigned areas of bush around the several villages for the use of the inhabitants of those villages. If a milpa is made beyond the designated area on Federal land, a tax is exacted by the Government. Milpas have been visited which were 8 to 12 kilometers from the village in which the milperos making them lived. The factors that seem to govern the selection of a site are: type of soil, ease of cutting the bush, nearness to the village, the presence of water, etc. There are undoubtedly differences in bush soils, though it is not easy to see the difference between what the milpero calls good and poor soils. There appears to be a size range in bush trees on either side of which cutting the trees is more difficult. Trees of more than say 15 centimeters diameter are not easily cut with the small axes of milperos. Likewise, small trees sometimes bend under blows of the axe and must be cut with machetes. Moreover, and perhaps of more importance, in bush made up largely of small trees, there are many more trees per unit area.

When milpas are made near a village, the milperos return to the village after their day's work. When a milpa is more than an hour's walk away—5 or 6 kilometers—the milpero usually moves to his milpa during the periods when he must work more or less steadily. In such instances, nearness to water, a cenote or a well, is of prime importance. The necessity of building a fence around a milpa, if near a village, where cattle and horses have free range, may often be a factor influencing the selection of a site far enough away to obviate the necessity for this extra labor.

Making the Milpa.—A site having been selected, the milpero cuts the bush in the early part of the dry season, November to January, and allows the trees to lie as eut until they are dry enough to burn. The largest trees are usually left standing. Among these are the ramon tree, the leaves and small branches of which are much used as forage for domestic animals, and the zapote, from which the chicle is obtained. The few palm trees, the leaves of which furnish the thatch for Maya huts, are almost never cut. The trees are usually eut at about waist height. Where fences are necessary, many of the smaller trees near the periphery of the milpa are left to be eut as needed for construction of the brush fence. In some milpas, some of the smaller trees are eut at heights of 2 or more meters, the stumps later serving as supports for the bean vines grown with the maize.

In March or April, before the rainy season, the cut and then dry bush is burned. The milpero waits for a day of relatively strong wind and starts his fire on the windward side of the milpa. By this time many of the stumps left standing have sprouts a meter or more long. This new growth is killed by the fire, and if the bush were a heavy one, the stumps and the large uncut trees may be killed, but usually, though considerably burned, many of them are left alive. Lundell, in his "Preliminary sketch of the phytogeography of the Yucatan peninsula," refers repeatedly to devastating fires which not only burn the felled bush but also sweep through the whole countryside. In this visit to northwestern Yucatan, absolutely no evidence of such forest fires was seen. Particular attention was given to this possibility throughout the trip; and in no instance was evidence found of milpa fires having burned for more than a few meters into the surrounding green bush. This study was made before the season of milpa burning, but one large milpa fire near Chichen Itza was watched. Even with a strong wind, the fire burned only the dry leaves and small dead trees for only a few meters beyond the felled bush; and the fire had ceased to burn in the uncut bush while it was still burning hotly in the trunks of the larger felled trees. Sometimes a milpero takes the precaution of removing the cut bush around the edges of his milpa for a few meters before setting the fire, but most often this precaution is to protect from fire his newly erected brush fence. And perhaps this measure is only apparently one of precaution; the fence is most easily built with the cut bush that is nearest it.

When the rainy season begins, which may be in April or as late as the end of May, the maize is planted. A sharpened stick, usually with a metal point, is used to make a hole in the ground. In this are dropped four or five kernels of maize. Seeds of a native squash and of the common bean (always a black-seeded one) or of a lima bean are mixed with the maize and all are planted together at random. No attempt is made to arrange the hills in rows, and they are spaced irregularly averaging probably a little less than a meter and a half apart. Not infrequently hills are planted in narrow rock crevices or in the deeper pockets in the surface limestone. If this were not done, considerable areas on the low knolls could not be planted at all. Maize seems to grow in rock crevices as well as trees do. In the deeper soils at the base of the range of hills in the western part of the area visited, maize is planted in rows about one and a half meters apart with hills not over half a meter apart in the rows.

Sprouts of tree stumps and weeds that appear in a first-year milpa are cut with a machete from once to three times during the growing season of the maize. Very rarely is this done three times and probably more often once than twice. By harvest time the weeds and sprouts have grown to a length of from 1 to 3 meters. When the maize ears begin to mature, the stalks are bent over below the ears, so that the upper part of the stalks, including the ears, hangs down; this is done, it is said, to protect the ears from rain and from birds.

The maize harvest extends over a considerable period of time. It is not uncommon for a milpero to harvest a basket of ears whenever the previously harvested basketful has been used up. By the early part of February, however, most of the maize has been harvested and stored. The ears are gathered into palm-leaf baskets, with the husks on, and piled near a thatched hut in the milpa. The part of the crop that is to be used or sold at once is husked and shelled. Ears that are stored for any considerable period are left in the husks. A crib of stocks is built a little above the dirt floor of the storage hut, and the ears are packed in it tightly in a vertical position with the tips downward. This method of storage is said to lessen injury from rodents and insects.

In preparing a milpa for a second crop of maize, the weeds, stump sprouts, and maize stalks are not cut early in the dry season as was the bush the year before. The cutting is delayed until toward the end of the dry season, it was said because:
(1) The small cut stems dry out quickly and therefore need no long drying period;
(2) if cut early, more weeds and stump sprouts would grow before burning; and
(3) the relatively small amount of trash does not produce a sufficiently hot fire to kill late-grown weeds and sprouts. As a matter of fact, this trash has to be piled as cut in order to insure its burning at all. A serious difficulty arising from this delayed cutting, seemingly overlooked by the Maya milpero, is that it affords time for the ripening and dispersal of an abundant crop of weed seeds which are not destroyed in any large measure by the fires which burn the piled trash.

The first-year milpa, having been cleared and burned, a second maize crop is planted and tended just as the first one was. For the reason noted above, the weeds on a second-year milpa are much more abundant than on a first-year one. On visiting a milpa it was rarely difficult to decide at once whether it was a first- or a second-year one, using relative abundance of weeds as the sole criterion.

Occasionally, maize is grown on the same milpa for three consecutive years. On the narrow belts of deeper soil at the base of ranges of hills, maize is sometimes grown on the same milpa for four years. But, in an overwhelming percentage of cases, two years is the limit. The milpa is then abandoned to return to bush and a new one prepared by cutting and burning another area of bush. The length of time that a piece of land is left in bush before being cut again for a milpa varies greatly. Rarely, this period is as short as four or five years, and in some instances it is as long as fifteen or twenty years. There is insufficient evidence upon which to base a positive statement of the average length of this bush period, but it is probably not far from ten years. It would seem that the essential factor is a length of time sufficient for the dominant trees to reach a size satisfactory for cutting, and to choke out the smaller bush, and incidentally the annual weeds also.


As in other places, maize yields in Yucatan vary from season to season. Throughout much of the area visited 1-1 1/2 cargas per mecate is a good yield for a first-year milpa, and one or a little less than one for a second-year milpa. It should be explained that a carga is 42 kilos, or about 93 pounds, approximately 1% bushels, and that a mecate is a plot of land 20 X 20 meters, or 400 sq. meters, almost one-tenth of an acre. While yields of 15 to 20 bushels per acre might well be regarded as unsatisfactory to a farmer in the corn belt of the United States, the surprising thing is that so good yields are obtained under the conditions prevailing in Yucatan.


That in general the yield of maize is somewhat less in a second-year than in a first-year milpa is everywhere evident. The bearing of this fact on the customary abandonment of a milpa after the second crop and its possible bearing on the withdrawal from a whole region by the ancient Mayas makes its cause or causes worth more than passing notice.

Soil depletion.—An opinion, apparently somewhat generally held, is that the system of agriculture now practiced by the Mayas results in rapid depletion of soil fertility. Lundell, in his "Phytogeography of Yucatan," says:

The ashes are the only fertilizer the soil receives, so it is quickly exhausted. Little humus remains after fires have swept the land. The crop is best she first year; the second year it falls off, and in either the third or fourth year the clearing is abandoned and another site is chosen. The abandoned milpas are again placed in cultivation after a lapse of several years, during which interval the fertility of the soil is partly restored by the rank vegetation. Apparently continued rotation leads to complete soil exhaustion ....

Since the trees of northern and western Yucatan are hardwoods, and ashes from their burning undoubtedly provide readily available mineral nutrients for the first crop of maize, it seems unlikely that there can be much leaching of these nutrients, for, even after the maize is ripe, the weeds and stump sprouts continue to grow and are not cut until late in spring. It is true also that the fire which burns the dried bush in preparation for the first-year crop burns the few leaves then on the ground and destroys some of the scant layer of humus. Rarely, however, does this destruction of humus extend for more than a couple of centimeters below the soil surface, and that far only where relatively large tree trunks have burned. The burning of stalks, weeds, and stump sprouts preparatory to the second crop has little effect on the remaining humus. This vegetation is so scanty that it has to be piled to insure its burning at all.

One with an agronomic background finds it difficult to believe that milpas, after two crops of maize, have been abandoned because of soil depletion, and equally difficult to conceive of soil fertility, once depleted, being restored by a few years of tree growth. Even without an agricultural background, one might reasonably question how such weeds as amaranths in a second-year milpa could grow to a height of 2-3 meters with a spread of branches nearly equal to their height if the soil were nearing exhaustion.

Weed competition.—In bush of several years standing, such as is felled for a first-year milpa, there are relatively few annual weeds, and these are found mainly along the narrow trails and in the more open parts of the bush. Many of the seeds of these annuals are undoubtedly killed by the intense heat of the burning slash. But some certainly escape, for there is always a considerable number of weeds in a first-year milpa. Since the earlier appearing weeds are cut usually only once, and that during the maize-growing season, weeds continue to grow long after the crop is ripe and are still flowering and only beginning to ripen seed in February; and since these late-growing weeds, along with the maize stalks and stump sprouts, are not cut until near the end of the dry season, there is opportunity for the ripening and dispersal of an abundant crop of seeds. Only a few large weeds may produce enough seed to stock the whole milpa. The burning of scattered piles of trash late in spring can have little destructive effect on the weed seeds which by that time are widely spread over the soil. The system is an ideal one for stocking the second-year milpa with noxious weeds. It seems almost too obvious to require statement that weed competition rather than soil depletion is the factor primarily responsible for the lessened yield of the second-year milpa. It seems equally clear that tree growth after abandonment of a milpa functions primarily in choking annual weeds rather than in restoring depleted soil fertility.

The labor differential between first-year and second-year milpas.—Statement of milperos agree that more time is required to cut the weeds during summer in a second-year than in a first-year milpa. Moreover, it takes materially more labor to cut, pile, and burn the maize stalks, weeds, and stump sprouts in preparation for a second-year milpa than to cut and burn the bush for a first year milpa. Only from careful records of labor requirements can this differential be accurately determined, but it would not be surprising to find that the preparation and care of a second-year milpa necessitate from one and a half to two times the amount of labor that a first-year milpa requires.


Dr. Steggerda's study of the dietary of the Maya Indians of the village of Piste indicates that maize furnishes about 85 per cent of the Maya's diet. The problem of food supply adequate for a given population is, therefore, largely one of how much maize can be grown in the region. Dr. Steggerda's records indicate that an average Maya family of five requires annually about 30 cargas of maize. In so far as can be determined from a hurried survey such as this, the usual yield of maize is I to somewhat more than 1 carga per mecate, and an average size of milpa for one family is probably not far from 40 mecates. It would seem, therefore, that the Maya now grows enough maize for his family plus what the chickens, dogs, and other animals eat, with some to sell to provide the family with the cheap cotton clothes they wear and the few other purchased articles they require.

Since a milpa is used ordinarily for only two years and then abandoned, and if about a ten-year interval in bush is necessary before the land is again used for maize, a crop can be produced on the average about one year in six. In other words, about 17 per cent of the entire area might be in maize each year. This statement is based on the assumption that none of the land is unsuited to maize production—an assumption that is almost literally true for the parts of the Yucatan peninsula covered in this survey. The water problem could be solved by artificial wells, such as are now in use. What percentage of this area is now in milpas in any one year is not known. But going over the country by rail, automobile, mule cart, and on horse-back, one is impressed by the very small fraction of the country in milpas. This impression was strengthened by observations made in going by air over the entire northern part of Yucatan from Merida to the east coast of the peninsula. While only by accurate records of sample areas can one obtain the necessary information, it would surprise the writer if such records, when obtained, show so much as 1 per cent of the land in milpa at a given time.

If this guess is not too wild to be credited, 15 to 20 times as much maize might be produced each year as is now grown, thus supporting that many times as large a population as is now found in the Yucatan peninsula, and this without changing the present system of milpa agriculture. No evidence was found in this short-time survey to indicate that the present system of milpa agriculture could not be maintained indefinitely. It would seem, therefore, that 15 to 20 times as great a population as the rather sparse one now in existence could find an adequate food supply. Even this figure would probably fall far short of the tremendous density of ancient population postulated by some archeologists in moments of ultra enthusiasm. The factual bases for such estimates are unknown to the writer and are perhaps beyond the powers of comprehension of a mere maize specialist. They do, however, call for a consideration of the possibilities that, in ancient times, a more intensive type of agriculture may have been practiced.

In the territory covered by this survey, there is no evidence of the type of intensive agriculture inferred from mountain-side terraces such as those seen by the writer some years ago near Inca remains in Peru. Of course, no such things are to be expected in a low and flat country such as northern and western Yucatan.

Whether the ancient Mayas employed fertilizers other than the ashes from burned trees or used partly rotted vegetable matter as a manure—as the present-day Maya Indians certainly do not—it is idle to guess.

The advanced civilization of the ancient Mayas would certainly have been capable of inventing tillage implements. They had no beasts of burden, but the postulated population should have furnished man power enough to obviate the need 0f horses or oxen. Even though the ancient Mayas had no metal tools, they could have made plows and cultivators, as they did axes and knives, from stone and hard wood. But why waste time on such details? Even our modern steel implements of tillage could not possibly be used anywhere in Yucatan except in the deeper soils at the base of the ranges of hills. Even if the outcropping rock did not incapacitate such implements in the first half hour of use, the rocks would keep them from reaching the intervening soil pockets. The main basis for the opinion that ancient Maya agriculture was much like present-day milpa agriculture is the fact that no other type can be regarded as having a chance of successful use. The Mayas of today use the only method available; and the ancient Mayas presumably used the same system for the same reason.

There remains one possibility not yet discussed. Could the ancient Mayas have kept the land in maize more than two years at a time, perhaps many more than two? Or, could they have shortened the interval during which the land was abandoned to go back to bush? By either of these ways the percentage of the whole area in maize at any one time could have been correspondingly increased. The agronomic problem involved in such longer or more frequent use of the land for maize is largely one of greater weed competition resulting in lessened yields or of more labor per unit area to hold the weeds in check.

Information obtained from Maya milperos indicates that it requires from one and one-half to two times as much labor to care for a second-year as for a first-year milpa. Cutting the weeds, stalks, and sprouts in a milpa as soon as the maize is mature enough to harvest, and thus before the weed seeds have ripened and been scattered, instead of waiting as at present until near the end of the dry season, should materially lessen the weeds to be fought the next season. But there is no way of knowing whether the ancient Maya's routine differed from that in vogue at present.

How much time does a Maya spend in caring for a milpa large enough to supply his dependents with maize for the year? If the ancient Mayas used materially more than one-sixth of the land for maize each year, could the milperos have devoted enough time to their milpas to meet the weed problem involved? A milpero cuts about two mecates of high bush a day. In cutting the trash in preparation for a second-year milpa, he covers about the same amount of land, but this takes the greater part of a day, while cutting two mecates of bush for a first-year milpa seldom requires all day. Two mecates seem to be the day's stint, irrespective of how many hours of work are required. Rarely is more than one mecate cleaned of weeds in one day's work during the growing season of maize in a second-year milpa. Under the present system, therefore, to prepare land enough for the maize needed by one family—say 40 mecates, or about 4 acres—and to weed it once in summer requires about sixty days of labor for one man. Burning the felled trees or the weeds and stalks, planting, and harvesting could hardly require more than twenty days. It follows that the present-day Maya milpero has about three-fourths of his time free from the labor necessarily connected with his milpa. The ancient Maya milpera grew cotton as well as maize, but the Maya of today grows enough more corn so that he can sell some in order to buy cotton cloth. Moreover, the ancient milperos must have grown enough maize for their priests and rulers in addition to the requirements of their own families. But even so, the ancients could have spent more time on their milpas than do their descendants of the present time, and still have had much time in which to build pyramids, temples, and the like. All this, if true, suggests that the present milpa system of agriculture, with only minor modifications, could have supported a very much greater population than is found today in the Yucatan peninsula—how much greater only careful long continued studies can determine.

What effects longer and more frequent use of the land for maize growing would have on soil fertility is beyond the writer's ability at guessing. Certainly soil erosion could have played no part in bringing about the abandonment of a low, flat region like that around Chichen Itza. There is no evidence whatever, so far as one who is not a geologist can determine, to indicate the presence of such "washes" as one sees commonly in the much drier regions, deserts, of California. But these regions are bordered by real mountains, not merely the low hills of Yucatan; and the steepness of their slopes is a surprise to any automobile driver who is likely to have his engine stall on what seems almost level ground.

The absence of erosion in northern and western Yucatan is no argument against the possibility that erosion was an important factor in causing the abandonment of the higher and more broken regions farther south where the old-empire Mayas flourished for a time only to abandon the area later and migrate to the low lands of Yucatan. Whether or not the erosion theory is the correct answer to the abandonment of the territory of the old-empire Mayas, it is now serving a useful purpose as the goblin of the present erosion campaign in the United States.


The survey here reported was only a preliminary study. Although statements of milperos are perhaps correct, many of the figures given here are at best only estimates and some of them are guesses, perhaps very poor guesses. At best a hurried survey could not be expected to do more than to indicate what the elements of the problem are and to suggest the kinds of accurate information needed.

The writer is convinced that weed competition and the labor involved in weed control is a more important factor than soil exhaustion, and yet, the latter might enter to a greater or less degree, particularly if the land were used for maize culture for relatively long periods and at relatively frequent intervals. The only way to get reliable information concerning the possible depletion of soil fertility by maize culture is to conduct, for several years, a carefully planned and carefully executed field-plot experiment. But this would require the services of a man trained in modern agronomic technique for at least part 0f each year, and of a trustworthy helper to keep detailed records during the growing season.

But there are problems of perhaps more immediate importance which should be undertaken at once, if their solution is of enough importance archeologically to warrant the expense involved. And, for the solution of these problems also, it is of prime importance to have a well-trained man with a well-founded agronomic background. Such a study should provide accurate information to take the place of the hear-say evidence, the estimates, and the guesses presented in this report.

It would seem sufficient to select six or eight sample areas, such as the territory contributory to Piste already studied in part by Dr. Steggerda. It is important to know the number of people gaining their support in a given area, the amount of maize produced and used for food by them and their domestic animals, or sold in order that other necessities may be purchased, the number of mecates cultivated in order to provide this maize, and the relation that the area of all the milpas bears to the entire area. Accurate information should be obtained also respecting the hours of labor per unit area devoted to each separate operation involved and in the preparation and care of milpas.

If a field-plot experiment is undertaken, one series of plots should be kept free from weeds at whatever cost, while another series is cared for as the Mayas now tend their milpas. Such an experiment should afford information not only in respect to possible soil depletion, as measured by maize yields, but the labor records should be of value in appraising the possibility that the ancient Mayas may have kept the land in milpas a greater percentage of the time than is now done.