An innovative technique
Fernando Penteado Cardoso**
No-till or direct planting is a technological procedure where planting is conducted on untilled land covered with residues. It aims to improve and conserve the soil, and is therefore an important if not fundamental technique supporting agricultural sustainability.
Based on the Bruntland definition of sustainable development,
“development that meets the needs of the present without compromising the ability of future generations to meet their own needs”, we can therefore define agricultural sustainability as follows: "development that provides economic feasibility, seeks efficiency, protects the environment and persists into the future".
It is quite clear that agricultural sustainability depends on a variety of factors. The RISE system, proposed by the Swiss College of Agriculture - University of Applied Sciences in Berne, analyses various factors which are the basis for agricultural sustainability: energy, water, soil, biodiversity, emissions potential, plant protection, waste disposal, cash flow (profit), investment and social/economic status, without classifying the importance or priority of any of them.
The issue of whether satisfactory soil fertility has a basic and important role in reaching the desired sustainability is unquestionable. This gives rise to the importance of No-Till Planting-NTP, a system made feasible by the invention of herbicides.
Improvement in the physical condition of the 20 cm layer can be obtained successfully using vegetative methods. If ploughing and harrowing break up the surface soil, root network clusters of grasses also do so when they decompose, leaving an extensive network of channels.
By avoiding tillage, we can avoid the inconvenient dispersion of clay which, after percolating, will form a lower and denser layer on top of the undisturbed soil. The plough or harrow provoke the so called hardpan which is sometimes confused with mechanical compacting, both undesirable because they reduce permeability and promote damaging surface run-off, even after light rain.
Production of residues and keeping them on the soil is clearly a basic aspect of successful no-till planting. A recent study of No-Till Planting based on 1500 random observations in Brazil"s main agricultural regions (1) showed that the end of the summer volume of residues on soybean and corn crops is far below desired levels, justifying a survey of the causes and the study of the solutions.
The research has already shown that suitable volumes of phytomass can be obtained by joint planting grass with commercial crops, as well as planting it in the final phase of annual crops or soon after harvest.
In damp, mild or warm autumn and winter regions, Brachiaria sown simultaneously in the corn or a few days later and whose development is controlled by growth regulators, has shown itself to be an efficient system. Recent studies show the feasibility of a similar joint planting scenario for soybeans, with definitive proof of good results from over-seeding slightly before harvesting. After harvesting the soybeans, other species such as millet are suitable. In regions with a cold and rainy winter, only winter grasses are viable, such as black oats and rye grass.
Oats, rye grass and fodder Brachiaria planted alongside or after summer crops can be used as pasture between commercial planting periods for meat or milk production. This system is called CCI – crop/cattle integration, when cattle farming and planting follow one another in the same area.
Both corn and sorghum, either as summer or double cropping, leave behind a satisfactory volume of residue, which is slow to decompose, unlike soybeans whose stubble quickly disappears. One parameter that can be adopted is a residue volume of 4 t/ha of dry material at crop planting, with 50% remaining at harvest time.
For permanent crops -- for example coffee or citrus -- introduction of the desired species, such as Brachiaria, Arachis or others, is followed by periodic slashing, ensuring that in the initial phase the covering plant does not compete for nutrients with the main crop.
After systematizing successive replacement, the residues protect the surface as well as improve chemical, physical and biological fertility of the soil, while also depressing invasive weeds through allelopathy.
Surface coverage reduces the speed of run-off, giving infiltration more time and avoiding erosion. It simultaneously controls temperature changes as well as evaporation intensity. It protects the soil from wind, avoids forming dust clouds which carry undesirable chemicals and nematoid eggs, additionally causing atmospheric pollution, dirty environments and contaminating respiration. This protection allows for planting in parallel lines, without dead rows, increasing the efficiency of planting, fertilizing and spraying operations.
Chemical properties are improved by the decomposing residue. Soluble humic acids bar Al toxicity in calcium deficient soil. The humus penetrates gradually, increasing retention of bases and water and reduces phosphorous fixation. This nutrient, if undisturbed for several years, forms an enriched and highly available layer, increasing the absorption coefficient. The residue forming plants recycle nutrients increasing their efficiency through slow-release and minimizing losses from leaching.
Humus and humic acids are favorable for clay aggregation, making the soil more porous, permeable and aerated, encouraging root formation and penetration, as well as multiplication of flora and fauna, all in search of food, oxygen and water.
The phytomass, in its various stages of decomposition, provides energy and nutrition to the flora and fauna in the soil. It increases the activity of bacteria and fungus which fixes nitrogen. Perforating insects proliferate thereby establishing galleries which encourage penetration of roots and water saturated with salts. Mycorrhiza flourish and, associated with the root systems, they increase nutrient absorption. A new biological equilibrium is created which in turn is unfavorable to pests and undesirable diseases.
The initially raw organic material continues to decompose and disappear, but the replacement of the residues, layer by layer, year after year, constantly renews it. That is, clearly, the main factor in the success of the no-till planting-NTP system.
NTP implementation may present difficulties which must be acknowledged and overcome. New and recently opened land is temporarily free of weeds, but requires removal of trunks and branches. Buried roots must also be removed, smoothing out the land, correcting calcium deficiencies and fertilizing are necessary. However, this is a favorable situation.
Older land, which is depleted and has been eroded, may present gullies along the sloping surface, exposed subsoil, denser layers, low porosity, a dormant stock of weed seeds as well as chemical deficiencies. They require special attention and acknowledgement of the cost of deployment and working in the first few years. These costs may include the loss of a crop season when a recovery period is required to restore physical properties, growing a grass preceded by subsoil scarification.
NTP over the years has shown direct and indirect economic advantages. A lower number of mechanized service hours are used, fertilizer and pesticide consumption is reduced and, most importantly, delayed planting, later than the best period, is avoided, as seeding can be restarted a few hours after rain. The biggest economic advantage however, is the improved fertility and productivity over a period of years, benefiting the current owners of the land as well as their successors.
NTP is the best method currently available for a conservation agriculture which is truly sustainable. It can initially be advanced by agricultural research concentrating on a solution to the aforementioned problems and others that may appear.
No till planting presents a new agricultural environment, it is a new crop system, a new philosophy of land management. It is a reliable, innovative and advanced technique. It is here to stay.
*Summary of the inaugural lesson of the Direct Planting Discipline, Department of Vegetable Production ESALQ-USP, on 11.08.08.
*Senior Agronomist, founder and former chairman of Manah S.A. (fertilizers and beef cattle), former Secretary of Agriculture for the State of São Paulo, Agronomist of the Year 1989 from AEASP, current president of the Agrisus Foundation – Sustainable Agriculture.
(1) Crop Rally Project-2008, with support from Agrisus.