Plant nutrition in soilless crops differs from that carried out in soils where root volume is muchsmaller and nutrient reserves are much smaller because the CIC of a substrate is much smaller than that of any clay. In most soils it is not necessary to provide all the nutrients while in a substrate crop we must provide them all and on a regular basis.

In a crop without soil the responses to changes are much faster than in a crop in soil, both for good and for bad. Therefore, the control that we can exercise in a substrate crop is greater than that we can exercise in a soil, but it also requires agreater ability to successfully carry out the cycle of our plants.

The ideal solution is one that provides the plant with both primary macronutrients and secondary macronutrients and micronutrients in the appropriate amount and form for the correct development of its crop cycle, respecting the optimal values of electrical conductivity, pH and salinity and taking into account the composition of the water that we are going to use in irrigation. At this point we must distinguish between applying fertilizer by quantity, and applying it by concentration; when working with concentrations the unit that we will use when referring to macronutrients is the meq/l (milliequivalent/liter) which is nothing more than the molecular weight multiplied by the valence. In the case of micronutrients, the unit of measurement shall be ppm (parts per million or milligrams/litre).

To design a correct nutrient solution for our plants we must have the nutrients that the water in our homes already carries, mainly calcium and magnesium. I put below a recent analysis of a water of a house in the province of Murcia.

I will briefly explain the parameters to take into account with the water of our houses:

  1. First of all, we see that the pH is at 7.2; normalmente in the waters of southeastern Spain the pH will oscillate between 7 and 8. This basicity of the waters is due to the content of bicarbonate ion (HCO3) which as we can see here is 1.98 meq / L. To lower the pH of this water we should neutralize the meq of bicarbonate with nitric or phosphoric acid, always leaving 0.5 meq of bicarbonate to guarantee a pH of 5.5.
  2. Electrical conductivity tells us the content of dissolved cations. This water has a ce of 0.6 dS/m which indicates that a fairly good water.
  3. Regarding a possible accumulation of undesirable ions in our substrates (salinity),the water has a sodium content of 2.57 meq/l, 2.7 meq/l of chlorides and 1.63 meq/l of sulfates. This must be taken into account when avoiding accumulations of salts that negatively affect the normal growth of our plants. As we will see later this is controlled with proper irrigation management.
  4. And finally, the nutritional issue; we see that the only nutrients to take into account when designing our fertigation solution are calcium (3.18 meq/l) and magnesium (2.41 meq/l). Theseamounts must be subtracted from the total calcium and magnesium that we intend to provide to our plants.

FERTIHOUSE VEGETATIVA.

Our vegetative solution has been designed in such a way that, at the dose of 5 cc / l, it provides the following balance of nutrients taking into account the contributions of water:

IONS

N TOTAL

NO3

NH4

H2PO4-

K

AC

Mg

SO4=

CL-

Meq/l

8.75

8.75

0,00

1.50

4.25

6.50

3.25

0,75

2,71

This equilibrium gives us the following relationship between ions:

NO3/K

2,06

3 vegetative

1.7 balanced

1.2 generative

As we appreciated and already discussed in the section dedicated to plants, the total nitrogen / potassium ratio is at a vegetative level.

Ca/Mg

2

The calcium/magnesium ratio is at the optimal value (2) so that both ions can be absorbed by the plant with the lowest energy expenditure.

NH4/N total

0,00%

As you have seen, the only nitrogen provided by the solution is nitric nitrogen, the fastest acting.

There are other forms of nitrogen such as urea and ammoniacal nitrogen; the first should not be applied on inert substrates since it requires the action of bacteria to transform it from urea (CO(NH2))2 to ammonia (NH3), from ammonia to ammonium (NH4+) and from this to nitrate (NO3). This process involves enzymes such as urease and bacteria such as ammonifiers and nitrifiers. But these enzymes and bacteria are not present in sufficient quantities in an inert substrate.

As for ammonium, it is an ion that can be phytotoxic in certain concentrations so its handling is reduced to certain times of the year and with the plant in certain phenological phases.

Lately you have heard the word nitrates relating it to the pollution of the Mar Menor, in Murcia, and this is not entirely true. The application of fertilizers such as urea are those that, at a certain moment of temperature and humidity of the soil, the bacteria find the ideal conditions to work and produce thetransformation of urea to nitrate (process not controlled or with nitrification inhibitors) and make available to the plant significant amounts of nitric nitrogen which will be used in a certain percentage (will depend on the type of plant, phenological status, etc.) ; the rest will be leached to the deeper layers of the contaminated soil aquifers. But this can be largely corrected by performing a correct fertigation with nitric nitrogen in the right amounts and at the times of the day when the plant is more predisposed to absorb nutrients. It is useless, for example, to apply a watering with fertilizer at night when the plant has the stoma closed; the cations will be fixed to a greater or lesser extent in the soil change complex, but the anions, such as nitrate, will be lost by gravity in the deeper layers of the soil.

K/(Ca+Mg)

0,43

0.35-0.6

For Ce<2

For a correct assimilation of the three main cations that our plants need, they have to be in a certain relationship depending on the final conductivity of the solution we provide to our plants. At 5 cc / l of FERTIHOUSE VEGETATIVA, the input conductivity of our solution to our pots will be around 1.8 with which the ratio K / (Ca + Mg) is perfectly located in the range of 0.35-0.6, being guaranteed the perfect assimilation of the three cations.

As for the final pH of our irrigationsolution, at the indicated dose it produces a pH between 5.5 and 6, the optimal for a correct vegetative growth of our plants. I want you to keep in mind that this pH is achieved with a water like the one I have shown you above; in other geographical areas and with other waters you must do a test before and measure the final pH with a pH meter.

GENERATIVE FERTIHOUSE.

This solution has been designed so that, in joint use with FERTIHOUSE VEGETATIVA achieve a lower N/K ratio and can be used to force greater flowering and at times of fruit filling.

At the dose of 5 cc/l of FERTIHOUSE VEGETATIVA and 1 cc/l of FERTIHOUSE GENERATIVA we obtain the following ionic balance in our nutrient solution:

IONS

N TOTAL

NO3

NH4

H2PO4-

K

AC

Mg

SO4=

CL-

Meq/l

8,5

8,5

0,00

1,3

6

6.50

3.25

0,75

2,71

NO3/K

1,4

3 vegetative

1.7 balanced

1.2 generative

With this solution we put our plants in a clear generative process (flowering and fruiting) without neglecting a sustained vegetative growth.

Ca/Mg

2

The calcium/magnesium ratio is at the optimal value (2) so that both ions can be absorbed by the plant with the lowest energy expenditure.

NH4/N total

0,00%

Again, the only nitrogen provided by the solution is nitric nitrogen.

K/(Ca+Mg)

0,6

0.35-0.6

For Ce<2

The relationship between the three main cations remains in the optimal range for balanced absorption of all three.

As for the final pH of our irrigation solution, at the indicated dose it produces a pH between 6 and 6.5, the optimal for a generative process.

Ion

B

Co

Cu

Faith

Mn

Mo

Zn

ppm

0,010

 

0,002

0,041

0,024

0,002

0,004

Both FERTIHOUSE VEGETATIVA and FERTIHOUSE GENERATIVA have the right balance between essential micronutrients.