| Sao Paulo, April 24, 2007
OPEN LETTER TO AGRONOMISTS
For the second time I address the agronomic community, and invite you to reflect upon the same subject: Conservation-Oriented Agriculture Based On No-Till Farming.
In April 1993, almost 15 years ago, I issued a vehement appeal to all my rural research, education and consulting colleagues, stating: “Analyze this issue with an unbiased attitude, with interest and with a sense of responsibility toward the problem. Soils have been formed in the course of thousands of years thanks to surface accumulation of residues. Their structure and biological life are based on the deposition of organic material, layer over layer, and through time immemorial time. We should not fear returning to the laws of Nature.” In April 2001 we organized the AGRISUS Sustainable Agriculture Foundation with the mission “To stimulate professional development and improvement, as well as to encourage agricultural research and rural extension programs, aiming at creating, developing and disseminating technologies conceived to optimize soil fertility in a sustainable and environmentally safe manner.”
On Agronomist Day, October 2006, as I celebrated at ESALQ my 70th graduation anniversary I ad-libbed a remembrance of my long career, stressing out outstanding facts I have witnessed, among which “the advent of herbicides that have allowed for the application of the no-till system, which is the best guarantee so far invented for maintaining soil fertility.”
We are facing a recent event, still another technology, as it refers to a new agricultural environment when we adopted the system of “unperturbed soil covered by residues” on 54 million acres.
We must accept and believe this new agricultural environment represents, in fact, a technological retrogression to primitive conditions, the time when mulch covered the soil surface.
Now, mechanized operations no longer destroy the fasciculate chain of canaliculi created both by hair-like roots and by the varied fauna that multiplies in a new and more favorable environment, with less temperature and moisture variations.
We no longer destroy the soil"s granulate structure through successive tilling, dissociating the aggregates and liberating clay that migrates to the subsoil, forming dense impermeable layers, the unwanted “plow pan”.
Disk plows and harrows no longer mix earth with phosphate-based fertilizers that are chemically stationary in the soil, and which are dislocated only by biological effects or carried by water through bioactivity-created galleries. High P-level sites are formed, thus altering the dynamics of root assimilation, as well as attenuating the problem of fixation.
As it facilitates penetration, we no longer lose water by run off, avoiding soil erosion and its harmful consequences. By infiltration waters feed water tables and, subsequently, deeper underground reserves. There is an increased outflow from water springs, underground reserves grow, and build-up of silt is avoided in streams, creeks and rivers.
The decomposing organic layer continually renews the humus and humic acids that permeate the porous interstice network, with beneficial effects for the soil"s physical and chemical properties.
Commercial crops, from the very early stages, are no longer submitted to stress caused by high soil temperatures and by extreme moisture variations.
We are facing a new and diverse agricultural environment of cultivated soil, a fact that is not always duly recognized. The tradition of mechanized soil prepping, with an iconic visual perception of a colorful tilled soil, is still embedded in our unconscious.
We must have the courage to change concepts, to renew the unconscious, to reformulate textbooks, to dare and eliminate the image of annual soil tilling. We are in a new phase of tropical agriculture, in a privileged nation that has no concerns over fast warming up of a soil still frozen by the winter.
We are still learning about this new agriculture in an unperturbed and residue-covered soil environment. There still is much to research so we can generate adequate technologies and become aware of the phenomena that regulate such technologies.
Let us define rules to satisfactorily renew the continually-decomposing layer. Let us investigate the ideal conditions for N-fixing bacteria and fungi, even when non-symbiotic. Let us define the soil-coverage plants that better re-structure the soil. Let us research species such as Brachiaria, which curb the fungi and nematodes harmful to cultures. Let us invent a new soil-sampling system to identify high-P sites.
Let us spread the word on this new agricultural production environment. Let us efficiently practice a tropical agriculture where it is warm and it rains, with dry periods that help harvesting. Let us, finally, create sustainable conditions for all that we have already achieved, as evidenced by the 130 million metric tons of grains projected for this year, with record production numbers in sugarcane, citrus products, coffee, meats, other fruits, pulses and flowers.
On the day of Agrisus" sixth birthday I send these invitations to my colleagues who have achieved so much for our agriculture and cattle industries. I congratulate them all.
Fernando Penteado Cardoso
Senior Agronomist, ESALQ-USP,1936