Healthy soil and sustainable growing

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ISIS Press Release 26/06/08
Ending 10 000 Years of Conflict between Agriculture and Nature

Organic agriculture is not enough; we must replace annual with perennial 
crops.
http://www.i-sis.org.uk/Ending10000YearsOfConflict.php
Dr. Stan Cox

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Humans now directly manage 27 percent of the Earth's surface area, harvesting 
more than 40 percent of the planet's biological productivity for our own 
uses. Yet food production per person is on the decline, and agriculture 
worldwide is doing more than ever to worsen the global ecological crisis. 
Like the Hindu god Shiva, today's agriculture is both a creator and a 
destroyer, partly as the consequence of conscious decisions taken by farmers, 
agribusiness executives, government officials, and food buyers. But the 
productivity and ecological impact of agriculture are also inherent in the 
crops and cropping methods that humans have relied upon for 10 000 years.
The problem of agriculture

Since its inception, agriculture has relied on annual plants that are grown 
from seed every year and harvested for their seed. That requires tilling of 
the soil, which can be done on a small scale without causing great harm, as 
in small, intensively hand-managed plots or on annually flooded land along a 
river. But every civilization that has practised tillage on a large scale has 
suffered the often catastrophic consequences of soil erosion [1, 2]. 
Industrialization has compounded the problem through burning fossil fuels and 
chemical contamination.

The world's natural landscapes are covered mostly by perennial plants growing 
in mixed stands [3], w hereas more than two-thirds of global cropland is sown 
to monocultures of annual crops . Conversion from natural to agricultural 
landscapes dramatically alters ecological conditions. Across the planet, more 
land has been converted from perennial to annual cover since 1950 than in the 
previous 150 years. This recent expansion of cropland has made it more and 
more necessary to apply chemical fertilizers and pesticides, which disrupt 
natural nutrient cycles and erode biodiversity [4, 5].

Perennial plants are highly efficient and responsive micromanagers of soil, 
nutrients, and water. Annual crops are not; they require churning of the 
soil, precisely timed inputs and management, and favourable weather at just 
the right time. With shorter growing seasons and ephemeral, often small root 
systems, annual crops provide less protection against soil erosion, wasting 
water and nutrients, storing less carbon below ground, and are less tolerant 
of pests than are perennial plant communities [6].

Today, vast swaths of entire continents have been scoured of their perennial 
vegetation, leaving the soil uncovered for a good part of the year. Even when 
the soil is covered during the growing season and even under organic 
management, lightly rooted annual crops fail to manage water and nutrients 
the way their deeply- and densely-rooted, persistent perennial antecedents 
did. Agriculture's destruction of perennial root systems has wrecked entire 
underground ecosystems, subtracting from the soil much of what makes it soil.

Agriculture is a problem older than history. It has always depended largely 
on annual grass and legume species that humans domesticated between 5000 and 
10 000 years ago. That domestication of annuals set in motion a somewhat 
ironic series of events. First, annual grain crops made civilization both 
possible and necessary. Much later, civilization - largely through 
exploitation of fossil fuels and synthetic chemicals - created conditions 
under which agriculture could become both extraordinarily productive and 
ecologically destructive. But today, it is the fruits of the very 
civilization made possible by agriculture - scientific knowledge, data, and 
techniques - that have clearly revealed to us both the necessity and the 
possibility of correcting the well-intentioned wrong turn our species made 10 
000 years ago [7](Jackson, 1980).
No-till, organic, and perennial

By far the most important factor that determines the degree of soil erosion 
in a field is the type of vegetation , annual or perennial , that covers the 
land. In one field experiment encompassing 100 years of data collection, 
perennial crops were more than 50 times more effective than annual crops in 
maintaining topsoil [8]. So-called “no-till” methods (in which annual crops 
are farmed without tillage) reduce soil loss but require heavy chemical 
inputs. No-till also performs as poorly as conventional farming in 
controlling percolation of nutrients and water out of the soil profile [9].

Global data for maize, rice, and wheat indicate that only 18 to 49 percent of 
nitrogen applied as fertilizer is taken up by crops; the remainder is lost to 
runoff, leaching, or volatilisation [10]. That occurs with or without 
tillage. Nitrogen losses from annual crops may be 30 to 50 times higher than 
those from perennial crops [9]. Organic farming with annual crops solves the 
problem of chemical contamination, but except in rare circumstances, requires 
as much or more tillage than conventional agriculture. And the inadequate 
root systems of annual species handle water and nutrients inefficiently even 
when crops are grown organically.

Modern societies, stuck as we are with annual crops, have little alternative 
but to treat grain cropping not as a source of life but as a dangerous 
activity against which humans and nature must be protected. Environmentally 
conscious researchers and farmers are making the most of the only perennial 
plants available to them, by growing more hay and pasture; growing perennial 
biofuel crops; planting more trees and grass along rivers and streams to soak 
up the contaminants that haemorrhage from cropland; and taking more erodable 
lands out of grain production altogether [11]. It's a monumental and 
discouraging task made necessary because we are still dependent on annual 
crop plants.

We cannot go back to the crossroads where our ancestors took that wrong turn, 
and a return to ancient farming methods would not address the problem of 
annual cropping. But by taking the successes of organic farming through 
another stage of evolution, it may be possible to produce food while 
simultaneously allowing the Earth itself to manage the soil, water, and air 
as it did before the dawn of agriculture.

To do that, we need perennial grain crops. Humans obtain three-fourths of our 
total calories from grains and oilseeds. By developing perennial grains, 
plant breeders could help dramatically enlarge that portion of the 
agricultural landscape that is kept intact by diverse, dense, and deep root 
systems. With a few very small-scale exceptions, no perennial cereal, pulse, 
or oilseed crops currently exist. But through a massive, long-term plant 
breeding effort, that situation can be resolved [12, 13].
The missing link in crop domestication

Neolithic people gathered and ate foods from a huge range of plant species, 
but once they began domesticating, it was annual plants like wheat, barley 
and rice that they transformed. Among the world's top 20 staple food crops, 
the banana is the lone non-woody perennial. Perennial grain species are not 
to be found anywhere among the world's crop plants [13].

Ancient grain-gatherers apparently did eat the seed of some perennials. 
Anthropologists have observed traditional methods of harvesting seed from 
perennial grasses in Poland , Mongolia and North America [14]. People living 
south of the Sahara harvested the seed of a wide range of perennial grasses 
[15]. The Vikings probably cultivated perennial lymegrass before barley 
reached Scandinavia [16]. Archaeologists have found charred seeds of three 
perennial and twelve annual species of small-grained grasses that people were 
consuming 23 000 years ago at a site in what is now Israel [17]. Yet no 
domesticated perennial grain species were handed down to us by plant 
domesticators.

Perennials were unlikely to follow neolithic people back to the fertile, 
churned soil around their dwellings in the way annual plants did. In any such 
situation, they would have been overwhelmed by the weedy annuals that 
specialize in colonizing such unfriendly territory by growing quickly and 
scattering their seed before dying. Meanwhile, in undisturbed natural stands, 
perennial plants re-growing from well-established roots and rhizomes would 
have been much more vigorous than new seedlings of the same species emerging 
from dropped seeds. People would have felt little incentive to sow a new 
generation of perennials as long as plants returned from previous seasons 
continued to produce well.

Changes in plant traits during domestication and breeding of annual crops 
occur through cycles of sexual hybridisation and selection. With annuals, the 
mechanics of food production and plant breeding are virtually identical. 
Through that process, Neolithic people domesticated annual plants without, at 
least initially, even realizing that they were doing so [18]. But collectors 
of perennial seeds, h arvesting year after year from the same perennial 
plants with no incentive to re-sow, would have had little or no genetic 
effect on the population.

Woody perennials became a part of the human diet, but h erbaceous perennials 
were left behind. But today, a small number of plant breeders are beginning 
to domesticate perennial species and hybridise them with annual relatives, in 
an effort to open the door to the kinds of dramatic changes in seed 
production and other traits that plant breeders have achieved in annuals.

The high yields of modern crops are the result of long-term, intense 
selection for improved harvest index (allocation of biomass to seed rather 
than vegetation) and decreased intraspecific competition. On the other hand, 
the relatively low seed yields of wild perennial species result from natural 
selection in highly competitive environments [19]. The evolutionary fitness 
of a wild annual plant is heavily dependent on seed production and dispersal, 
but the fitness of a wild perennial depends more on the survival of 
vegetative structures than on seed traits. Therefore, it's not surprising 
that many (but not all) wild perennials have low seed production.

It is predicted [19] that artificial selection in a properly managed 
agricultural environment could increase seed yield while maintaining the 
perennial trait. Artificial selection has the potential to generate perennial 
grain crops with acceptable yields, if it is applied to agronomic traits and 
perennial growth habit simultaneously. This is suggested by four 
characteristics of perennial plants that differentiate them from annual 
plants and provide them with extra resources that can be re-allocated to 
grain production [13]:

    * A longer growing season
    * More conservative use of nutrients
    * Generally higher biomass production both above- and below-ground
    * Sustainable production on marginal lands

Current perennial-grain research

Through our research at The Land Institute, we have concluded that, unlike a 
field of maize or soybean, a field of perennial grain-bearing crops can 
provide food while at the same time protecting soils, water, and 
biodiversity. The genetic raw material is available, ready to be put to use. 
The Land Institute and a few universities and other agencies have created the 
foundations of breeding programmes that will, over the next decades, develop 
a wide array of perennial grain crops. Most current genetic and breeding 
effort is going into the following species and species hybrids.

Intermediate wheatgrass ( Thinopyrum intermedium ) is a perennial relative of 
wheat ( Triticum aestivum ). We are domesticating this species by breeding 
for increased seed size, seed yield, and ability to thresh freely. The main 
approach is to evaluate thousands of individual plants over two years, 
followed by a third year crossing the 5 percent of best-performing plants. We 
have completed one cycle and are now in a second. Experiments have shown that 
the first round of selection increased mean yield by about 18 percent and 
mean seed size by about 10 percent. Some individual families perform much 
better. In a separate population, four fast cycles have increased the 
fraction of free-threshing seed from about 8 to around 30 percent.

Wheat and triticale (X triticosecale ) can be hybridised with several 
different perennial species. We have crossed these annual species with 
perennial relatives, primarily intermediate wheatgrass, and backcrossed to 
the annual to produce thousands of relatively fertile, large-seeded plants. 
In the greenhouse, a large proportion of these plants continue to live after 
their mature seed has been harvested, but in the field we have so far only 
identified about 10 plants out of thousands that were able to re -grow after 
harvest.

 To obtain larger numbers of perennial plants, we have crossed hundreds of 
interspecific hybrid plants to the perennial parent, wheatgrass. We produced 
hundreds of hybrids, but many of them were sterile, as expected. We have 
since crossed the few plants that produced viable pollen with pollen-sterile 
plants in an effort to restore fertility. A few resulting plants have 
exhibited good fertility, large seed, and vigorous regrowth.

Grain sorghum , a drought-hardy feed grain in the US and a staple food in the 
Eastern Hemisphere , can be hybridised with the tetraploid (4 sets of 
chromosomes, 4 x 10 = 40) perennial species Sorghum halepense . We have 
produced large plant populations from hundreds of such diploid (usual 2 sets 
of chromosomes) x tetraploid hybrids. The better strains currently produce 
about 40 percent of the grain yield of their annual grain sorghum parents, at 
half their seed size; this is a fourfold improvement over S. halepense and 
represents some of the largest seed of any perennial grain in development. 
Being a tropical plant, sorghum survives the winter in temperate regions 
through the survival of rhizomes, or underground stems. Rhizome development 
is a complex genetic trait, dependent on 9 of sorghum's 10 chromosome pairs 
[20]. Winter survival is even more complex, and harder to achieve through 
breeding. However, we have found no strong negative correlations between 
these components of the perennial trait on the one hand and grain 
productivity on the other.

Illinois bundleflower ( Desmanthus illinoiensis ) is a native prairie legume 
that produces relatively large harvests of protein-rich seed [21]. It is a 
strong candidate for domestication as a crop. The Land Institute has 
assembled a large collection of seed from a wide geographical area and 
initiated a breeding program. Making controlled hybrids is extremely 
difficult technically, but methods have been developed to foster natural 
hybridisation and identify hybrids using morphological or molecular markers. 
Non-shattering families – crucial to domestication – have been selected and 
used as initial parents. The species is a strong, widely adapted perennial, 
and selection criteria will include shattering resistance, synchronous 
maturity, seed yield, and seed size and quality.

Maximilian sunflower ( H. maximiliani ) and Kansas rosinseed ( Silphium 
integrifolium ) are native perennials related to sunflower. The Land 
Institute is in the process of domesticating these species as perennial 
oilseed crops, via methods similar to that described above for intermediate 
wheatgrass. There is a parallel programme for inbreeding to expose rare, 
valuable recessive genes. Phenotypic variation is extensive in these species. 
In addition to the usual traits, selection pressure is being applied to fuse 
the numerous small seed-heads into larger, more compact heads and eliminate 
seed dormancy. In the case of the large-seeded Kansas rosinseed, selection to 
increase seed fertility of the head is in progress.

Sunflower ( Helianthus annuus ), the highly productive annual oilseed crop, 
can be hybridized with several perennial species in its genus, including the 
diploid (2 x 17 = 34) Maximilian sunflower and two hexaploid (6 x 17 = 10 2 ) 
( ? )species: rigid-leaf sunflower ( H. rigidus ) and Jerusalem artichoke ( 
H. tuberosus ). Hybrids between annual and Maximilian sunflower are highly 
sterile, unless their chromosome numbers are doubled to produce tetraploids. 
The best strategy to produce perennial, partially fertile plants is to cross 
both annual and Maximilian sunflower to the hexaploid species to produce 
tetraploid plants and then inter-cross the different tetraploids. Large 
perennial populations have been produced in this way, and they are being 
subjected to selection for greater seed fertility.

There are many more groups of species that could be used to develop perennial 
grains [12].
A new organic agriculture

The perennial grain crops listed above and others are intended to be grown in 
a food-producing system that replicates as closely as possible the ecological 
functioning of the natural landscape it replaces; in The Land Institute's 
case, the prairie grassland. In other regions, different sets of perennial 
crops can be used with similar effect, to be as hardy and resilient as a 
forest or a savannah, or whatever ecosystem preceded human habitation in a 
given region. What all such future systems have in common is that they will 
be based on perennial plant communities with ample genetic diversity both 
among and within species, and t he energy that supports them will be the 
sunlight that falls directly on them. They must function independently of 
fossil energy and synthetic chemicals.

Researchers in organic and sustainable agriculture research have, out of 
necessity, attempted to mitigate the impact of agriculture by improving what 
I'll call the “software”: the application of experience, knowledge, 
techniques, and natural materials to existing annual crop species. But those 
annual species represent a kind of dysfunctional “hardware” that limits what 
can be achieved with even the best agricultural “software.” To open up 
possibilities for truly new agriculture that is sustainable in the long term, 
new hardware – a wide range of perennial grain crops - is needed.

Plant breeders have long had difficulty finding their role in organic and 
sustainable agriculture. Now we have a clear-cut, difficult, but achievable 
mission laid out for us: to develop perennial crops that can make agriculture 
truly sustainable for the first time ever [22]. It will require a huge effort 
that must extend far beyond The Land Institute to agronomy, horticulture, and 
plant breeding departments in institutions across the globe. Plant breeders 
live in the future. Even in well-established crops, the pollinations we made 
this spring or summer won't lead to cultivars until we are well into the next 
decade. Breeding varieties and hybrids only for currently available farming 
systems becomes a self-fulfilling prophecy. Plant breeders in organic 
agriculture, indeed all plant breeders, must instead work toward goals that 
will be important in the longer term. And that “longer term” will by 
necessity include perennial grain crops.

Dr. Stan Cox is Senior Research Scientist at The Land Institute, Salina, 
Kansas, USA .