Crop requirements

 One of the benefits of conventional agricultural science is that it teaches us about the nutrient requirements of each vegetable. In Quebec, this information is compiled in the Fertilization Reference Guide that most agronomists have. Combined with soil analysis results and NPK analysis (nitrogen, phosphorus, potassium) of amendments, these data allow a calculation to be made. which specifies the quantity of fertilizer to appmter to the gardens. The exercise is a bit complex and it is one of the good contributions that a agronomist can make a fertilization plan. Good of course, this is a very theoretical way to proceed and I don't see how the equations can translate the complexity of the many interactions biologicals of cultivated soil. Nevertheless, it is a technique which has the merit of evaluating the quantity amendments necessary for a culture and, in this sense, it is very useful. The fertilization plan of our farm was also developed in prutia using of these calculations.

That said, you should not be too worried if the fertilization of a vegetable garden is not directly the result of these calculations. More recommendations general guidelines can be used and supplemented by monitoring in the field. Ultimately, it is the observation of the plant and the success of a crop that whether or not they support a recommendation from fertilization. It is good to keep in mind that a improper fertilization is as damaging as deficient fertilization.

The elements of fertility

To acquire know-how in the fertilization of its crops, you have to know the elements that make the soil fertile. This is what I propose to do in this chapter. For a more complete presentation and exhaustif on the subject, I recommend that you read The bases of crop production, from Dominica Soltner. The book by Denis Lafrance, The organic culture of vegetables, which includes a chapter on soils and fertilization, is also very informative.

Organic matter (OM)
Organic matter plays a fundamental role in the fertility of a soil. When mineralized by biological activity, it releases nitrogen, phosphorus, sulfur and several trace elements that provide food for plants. What is not not mineralized accumulates in the soil and comes to constitute its structure. For all living organisms in the soil, organic matter is used for both fuel and habitat. Organic matter and biological activity are therefore closely related. The level of organic matter is one of the main information provided by a soil test.
With this information in hand, we must then manage organic matter in its soil in three ways:
~ Build your soil, that is to say add an important initial input of organic amendment for obtain a high organic matter content in its gardens. To achieve this, the foam peat is often an excellent choice.
~ Maintain soil fertility by compensating for loss of organic matter due to mineralization, tillage, extraction of vegetables and erosion. This is the main reason for incorporating compost, fertilizers greens and crop residues in the soil.
~ Ensure that a level of organic matter raised in its soil is not the result of insufficient biological activity due to soil acidic or poorly drained, as this would mean that organic matter accumulates instead of break down. Even though the results may look good on paper, you may need to improve material availability organic in the soil by improving its physical characteristics.

In Quebec, most soils are slightly acids. As a pH below 6 inhibits the development of microbial life and impairs the activity biological in general, it is often necessary to correct this acidity by adding limestone amendments such as wood ash and agricultural lime. The latter is the most common and it is the one we use in our gardens. Agricultural lime is a heavy white powder obtained from a rock crushed. It is a natural ingredient that works rather slowly, which is a good thing.

The optimum pH for most crops is between 6 and 7, and generally aiming for a goal of 6.5 is ideal. To increase the pH of its soil with lime, it is necessary to gradually incorporate small doses so as not to change the soil structure too abruptly. In this regard, it is important to respect agronomic recommendations. He It is also important to check the evolution of the pH before each application to ensure that the treatment is appropriate - hence the importance of carrying out a soil analysis beforehand. Once the goal of pH reached, the regular addition of compost, often slightly alkaline, should cause the pH maintains itself. In our gardens, we let's apply the lime by broadcasting it on the surface, then incorporating it in the first 15 centimeters of the soil using the rototiller.

Nitrogen (N)
Each year, the organic matter present in the soil will provide a certain amount of nitrogen by the mineralization, but depending on the crop, it could prove to be insufficient or not available at the oppmtun time. As there is a relationship direct relationship between a good nitrogen supply and growth vegetables, care must be taken to ensure that the crops do not not lacking. The compost and manure we add in the garden must be rich in nitrogen to ensure adequate fertilization. The amendments did not not all the same f1tilising value and must therefore be culturally appropriate.

Nitrogen is an element which mainly favors the leaf development of plants. It must therefore be quickly available to crops after their implantation, when they develop their foliage. When we use organically, we must remember that mineralization is only possible in warm soil. Usually below 10 ° C (temperature of the soil and not of the air), the biological activity of the soil becomes very low, even non-existent. It is for this reason that in the spring, when the floors are still cold, you have to compensate the potential lack of nitrogen by adding fertilizer soluble at the start of cultivation to ensure that the crops will experience good growth. Flour blood, fish emulsion or chicken manure are examples of fertilizers that will provide nitrogen faster than compost.

Likewise, do not fertilize your crops with a nitrogen rich amendment when temperatures are too cold, for example at the end of the season. In fact, nitrogen accumulates there in the form of nitrate and can make vegetables poisonous. In period of low light intensity, fertilization late crops, such as winter spinach and other greenery grown in a tunnel, pose this kind of problem.

Phosphorus (P)
Phosphorus contributes directly to the root development of vegetables at the start of growth and, in general, it plays a leading role in the formation and ripening of fruits and tubers. This element is also produced by mineralization of organic matter and, by therefore, any practice that improves the biological activity of the soil promotes greater availability phosphorus to plants. Regular application
of compost and manure provide the soil with a reserve sufficient phosphorus to meet the needs vegetables. Rather, it is the misuse of this element that is of concern.

Phosphorus is not very mobile in the soil, and vegetables need less than nitrogen. If crops are used with amendments of animal origin (in order to fill their nitrogen requirement), phosphorus can accumulate rapidly in the soil and then be lost to the environment through leaching and runoff. It is this pollution that is responsible for the eutrophication of waterways located near farming lands. Green manures are a solution to overcome this problem. Indeed, they allow to add nitrogen to crops, without addition of phosphorus.

Potassium (K)
Potassium is the last element of the famous NPK equation (nitrogen, phosphorus, potassium). He has a role to play in the preservation of root vegetables and it has a positive effect on the size, color and even the taste of fruit vegetables. He gives back also vegetables that are more resistant to disease, parasites and bad weather, thus contributing to their vitality.

Unlike nitrogen and phosphorus, potassium does not come from the mineralization of organic matter. It is already in the ground at the mineral state, mainly in the form of clay. Assimilable potassium is very soluble in the soil, which makes it readily available to plants, but also easily washable. This is one of the first things to go away when a bunch of com posts are left uncovered.