Essay - jan/feb 2006
James C. Delouche
Professor Emeritus Mississippi State University
Ecology was an almost forgotten subject when I was in college. I did take a course in Crop Ecology in graduate school but remember that it was more crop geography than ecology. The course dealt primarily with where and how various crops were grown with little attention to why they were grown where they were grown, i.e., why is rice the major food grain crop in the humid sub-tropics and tropics while wheat is a dominant crop in temperate and cooler climates? Perhaps, the professor felt that the reasons were so obvious that there was no need to consider them. While that was my only formal academic exposure to ecology, much later I began to realize that there was a lot of ecology in physiology, mycology, biochemistry, economic botany, even genetics and other subjects I had studied, especially in seed biology. Ecology is no longer forgotten or ignored. It has become an increasingly well known, popular and very fashionable subject since environmental concerns and issues began their ascent to high priority positions in socio-economic and political debates at national and international levels about 40 years ago, and ecology and the environment began to be viewed by many as synonymous. These changes have good and bad aspects. I t is very good that the importance of environmental settings, i.e., the ecology, ranging from from deserts to wetlands, from forests to artic snow to the well being of living systems including "us" is now so widely recognized and appreciated. But, it is unfortunate that environmental and ecological concerns and issues are being considered and addressed in the aggressive and simplistic ways of some of the extremists. Surely, the opposing views will merge into commonsense positions as those on opposite sides of the important environmental issues not just appreciate but gain a better, more realistic understanding of the complex, beautiful and seemingly miraculous interrelationships of the environment and living systems that characterize planet earth. Planet earth, however, is much too ambitious a subject for this essay and essayist so let us focus on something smaller, the seed.
Seeds Roles in Ecosystems
Seeds have crucial roles in the maintenance, regeneration, and migration of plant populations and communities including those of crop agriculture. In fulfilling these roles with near perfection as they have and do seeds reveal and display awesome capabilities for surviving adversities, adapting to change, and taking advantage of opportunities to augment their number, distribution and competitive capacity. Seed ecology is concerned with the survivability, adaptability and opportunism of seeds in carrying out their regenerative roles in the incredibly diverse ecosystems where plants live and reproduce ranging from tropical rain forests to near deserts, from intensively cultivated crop-lands to native grasslands. Seed ecology and seed physiology merge into seed eco-physiology in many of the reactions of seeds to environmental settings and their interactions with various components of the environment. In agriculture seed ecology or ecophysiology is especially concerned with the performance of seeds in any sort of crop culture, advanced or traditional. Obtaining a good or at least an acceptable performance from seeds sown to produce crops has long, perhaps always, been viewed as the crucial first step in crop production. Historically, much of the technology and a lot of the effort in crop agriculture have been directed at providing the best possible "ecological" setting for good seed performance - germination, seedling emergence and establishment - of the crops produced. Seed bed preparation, i.e., preparation of crop land for sowing, was given so much attention in such detail in some of the agronomy and horticulture courses I took that it was more like creating a work of art than a place for sowing seeds. This passion for the "seed bed", however, began to cool substantially in the final quarter of the last century as a result of changes in both traditional and advanced cropping systems that have produced new demands and opportunities in crop establishment.
No tillage system requires seeds with higher performance
Changes in the Ecological Setting of Crop
The relatively recent and continuing changes in crop agriculture have been substantial and numerous. Crop production is being extended into areas that are cooler and warmer, drier and wetter, shorter and longer in growing days, and more saline or higher in toxic elements, e.g. aluminum, in order to compensate for the shrinking arable land base. There is a continuing shift from reliance on agri-chemicals for pest control to genetic engineering, from intensive cultivation to conservation tillage and no tillage, and in some areas to organic farming. Seeding rates are decreasing due to higher seed prices. Precision planting to establish an optimal population geometry is "practiced" for some vegetable crops and is being evaluated for agronomic crops. Pastures and other grasslands are being renovated to introduce and establish more productive and nutritious species in some areas, while in other areas efforts are underway to restore the native species in grasslands. These changes like all changes have consequences. The establishment and maintenance of optimum, even adequate, populations of plants under the changes taking place in cropping ecosystems is placing enormous demands on the generative and performance capabilities of seeds. Meeting these demands will require changes and improvements in the ways seeds are produced, processed, treated and sown. The improvements needed, in turn, will have to be based on and fully take into account the eco-physiology of seeds.
A few years ago I attended a workshop for soybean and cotton farmers in the process of changing from full, conventional tillage to minimum or so-called conservation tillage systems. The topics that received the most attention were obtaining a stand of plants and control of weeds. Some farmers felt that treatment of soybeans, which is not a usual practice in conventional tillage systems, was essential in minimum or no-tillage systems. Others felt that in addition to seed treatment, close monitoring of the soil temperature and moisture status was critical to ensure that they are at favorable levels for planting. There was also a lot of discussion on the effects of different options in the minimum tillage system such a narrow or conventional row spacing, early and conventional dates of planting, irrigation or non-irrigation, and rotations with other crops on stand establishment and, of course, on crop growth and yield. Another topic that frequently entered the discussions was the increasing costs of seed, especially GM seeds, and, thus, the urgent need to avoid the losses associated with less than adequate plant populations and the multiple costs of replanting. I left the meeting with a great, a very great appreciation of the increasing complexity of crop agriculture and thankful that I was retired and did not have to struggle for answers to the many difficult questions from the participating farmers as the specialists leading the workshop often had to do.
Diversity in Crop Ecosystems
Farmers in Texas sow sorghum seeds treated with fungicides and an antidote for a specific herbicide with huge planters in narrow or conventionally spaced rows. Farmers along the shores of Lake Chad in Central Africa hand plant and water sorghum seeds in special beds so that seedlings will be ready for transplanting on land bordering the lake to take advantage of residual moisture as it emerges with recession of the water, i.e., drying of the lake. In Mississippi cotton farmers sow delinted, treated, density graded, GM cotton seed in conventional or minimum tillage systems when the soil temperature at seed depth has been above 18º C for several days. In China farmers plant non-delinted, often untreated cotton seed in soil in small, plastic film containers, which are gathered together under plastic film shelters, i.e., miniature "glass houses", to produce two or three week old cotton seedlings for transplanting that allow the extension of cotton production northward into areas too cool for conventional planting. Along the Congo River also in Central Africa farmers broadcast rice seeds by hand among felled trees for producing crops for 2 to 3 years before moving on to another site, while in Louisiana rice seeds are sometimes sown by air into fields with a thin flood of water, i.e., water-seeding, because of adverse weather that prevents the use of ground equipment and/or to deal with severe red rice infestations. The point of this litany of diverse and contrasting cropping systems is this: although the systems are incredibly different, the seeds planted to produce the same crop are essentially the same. Up to the present time there has not been a significant improvement in the innate generative qualities of seed systems.
Traditional Agricultural Concerns in Seed Ecology
In agriculture seed ecology has been concerned both with the establishment and/or regeneration of the plants that are desired, the crops, and those that are not desired, the weeds that infest crops. The cultural practices traditionally used in crop production are about equally divided between those that favor and enhance the establishment of the crop and those intended to minimize or prevent the establishment of weeds. Much of the good descriptive and quantitative informational base in seed ecology relates to the migration and regeneration of plant communities and populations in non-cropped or marginally-cropped areas such as pastures, rangelands, other grasslands, woodlands, wetlands, and so on. In recent years, however, some very good information has been developed by weed scientists seeking more efficient and effective ways to control the weeds that infest crops. Some of the findings from this research and its broader implications in crop agriculture will be reviewed in the next part of this essay.