We find one of the most cultivated and consumed crops in the world. It is the queen of salads and one of the easiest products to consume. Therefore, it is important to know the lettuce fertilizer thoroughly . 

With regard to agriculture, lettuce is a simple plant to grow but with adequate control of irrigation and fertilization.

At least in winter , the nutrients must be available at all times so that their growth does not stop. The environmental conditions are not the most appropriate and, therefore, in terms of cultural work we cannot have faults.

Among the  most common varieties of lettuce  we can find Iceberg, Romana, Trocadero, Oak leaf, Lollo blanco, Lollo rosso, etc.

The nutritional needs of all these are usually the same, varying in the way of irrigation and the concentration of nutrients by stages, since some are of earlier harvest or have a longer or shorter cycle depending on the case.

GROWTH AND DEVELOPMENT PHASES OF LETTUCE

When fertilizing the lettuce, we can distinguish different phenological phases. The role of nitrogen is important and we have to know how to control it depending on the stage of development of the lettuce.

• Initial phase:  corresponds to the germination of the lettuce and the first vegetative stages. Normally this stage usually happens in the seedbed.
• Development phase:  stage that ranges from when we transplant (after seedling) until the lettuce rosette is formed.
• Cogollado phase:  when we have the rosette of the lettuce until a complete bud is formed.
• Reproduction phase:  a stage where the cogollado ends and the heading or formation of the flower stalk begins. From an agronomic point of view, we are only interested in this phase if we want to take advantage of the seeds.

HOW LONG DOES THE CULTIVATION AND FERTILIZATION OF LETTUCE TAKE? 

The cultivation and fertilization of lettuce is determined by the climate.

As there are different varieties, each one adapts to different cycles depending on how hot or cold it is.

For short cycle varieties , this phase lasts between 50 and 70 days in summer and 80 to 90 days in spring.

For long-cycle varieties ,  that is, those that are grown in cold months, lettuce cultivation can last 100-120 days in winter and 90-100 days in autumn.

NUTRIENT ABSORPTION BY LETTUCE

Not all the nutrients that a lettuce cycle needs we have to contribute to the soil. Others can be obtained directly from the soil or from the initial contribution of organic matter (a not inconsiderable contribution).

We are going to see, element by element, the behavior of each one and its absorption in the lettuce fertilizer. 

NITROGEN IN LETTUCE FERTILIZER

Of all the nitrogen available in the soil, most of it is provided by organic matter in its mineralization.

Depending on the irrigation that is given or the rain, we will have a proportional part of the ammonia phase (NH4 +) fixed in the colloidal complex and the nitric form (NO3-) free in the soil or leached.

Therefore, we have to make the greatest contributions in nitric form , the form of nitrogen that is most absorbed by plants.

The plant absorbs nitrogen from the moment of transplantation , having an ascending assimilation until the harvesting phase.

Let’s put a long cycle lettuce, 120 days and the most common, iceberg. This is how the nitrogen uptake is distributed.

• 1st and 2nd week after transplantation: 1 FU / ha or 1 kg / ha of nitrogen (eq. To 2.89 kg ammonium nitrate 34.5%).
• 3rd and 4th week after transplantation: 4 FU / ha or 4 kg / ha of nitrogen (eq. 11.59 kg of ammonium nitrate 34.5%).
• 5th and 6th week after transplantation: 6 FU / ha or 6 kg / ha of nitrogen (eq. To 17.39 kg of ammonium nitrate 34.5%).
• 7th and 8th week after transplantation: 9 FU / ha or 9 kg / ha of nitrogen (eq. To 26 kg of ammonium nitrate 34.5%).
• 9th and 10th week after transplantation: 12 FU / ha or 12 kg / ha of nitrogen (eq. To 34.78 kg of ammonium nitrate 34.5%).
• 11th and 12th week after transplantation: 18 FU / ha or 18 kg / ha of nitrogen (eq. To 52.17 kg of ammonium nitrate 34.5%).
• 13th and 14th week after transplantation: 20 FU / ha or 20 kg / ha of nitrogen (eq. 57.97 kg of 34.5% ammonium nitrate).
• 15th and 16th week after transplantation: 25 FU / ha or 25 kg / ha of nitrogen (eq. At 72.46 kg of ammonium nitrate 34.5%).

PHOSPHORUS IN THE LETTUCE FERTILIZER

Lettuce absorbs phosphorus in the form of monovalent phosphate (PO4H2) although it also finds other less important forms of absorption.

It is used in abundant quantities in the rooting and seed germination phase, since it favors the accumulation of reserves.

When the plant is in a stress situation (cold, cold water, etc.), the plant absorbs a good amount of phosphorus, which must be in available conditions to facilitate the increase in size.

However, in the general case of lettuce , its consumption is low and the amounts provided should not be very high.

Let’s make a study of phosphorus assimilation in the lettuce fertilizer according to the planting phase where we are.

• 1st and 2nd week after transplantation: 0.1 UF / ha or 0.1 kg / ha of phosphorus (eq. To 0.2 kg of phosphoric acid).
• 3rd and 4th week after transplantation: 0.2 UF / ha or 0.2 kg / ha of phosphorus (eq. To 0.38 kg of phosphoric acid).
• 5th and 6th week after transplantation: 0.5 UF / ha or 0.5 kg / ha of phosphorus (eq. To 0.96 kg of phosphoric acid).
• 7th and 8th week after transplantation: 0.8 UF / ha or 0.8 kg / ha of phosphorus (eq. To 1.54 kg of phosphoric acid).
• 9th and 10th week after transplantation: 1 FU / ha or 1 kg / ha of phosphorus (eq. To 1.92 kg of phosphoric acid).
• 11th and 12th week after transplantation: 2.5 UF / ha or 2.5 kg / ha of phosphorus (eq. To 4.8 kg of phosphoric acid).
• 13th and 14th week after transplantation: 4.5 UF / ha or 4.5 kg / ha of phosphorus (eq. 8.65 kg of phosphoric acid).
• 15th and 16th week after transplantation: 6.3 UF / ha or 6.3 kg / ha of phosphorus (eq. To 12.11 kg of phosphoric acid).

POTASSIUM IN LETTUCE FERTILIZER

Potassium is an element of great mobility and absorption by lettuce. It is absorbed in ionic form (K +) and organic matter, in its mineralization process, contributes enough of this element.

It is, without a doubt, the nutrient most consumed by the plant , above nitrogen. Its consumption is between 150 kg / ha of potassium in less vigorous varieties and 200 kg / ha of potassium in the most vigorous and large ones.

Let us do a distribution study again in the absorption of potassium in the lettuce fertilizer.

• 1st and 2nd week after transplantation: 1.5 UF / ha or 1.5 kg / ha of potassium (eq. To 3.26 kg of potassium nitrate).
• 3rd and 4th week after transplantation: 4.5 UF / ha or 4.5 kg / ha of potassium (eq. To 9.78 kg of potassium nitrate)
• 5th and 6th week after transplantation: 6 FU / Ha or 6 kg / ha of potassium (eq. To 13 kg of potassium nitrate).
• 7th and 8th week after transplantation: 16.2 UF / ha or 16.2 kg / ha of potassium (eq. To 35.21 kg of potassium nitrate).
• 9th and 10th week after transplantation: 24.3 UF / ha or 24.3 kg / ha of potassium (eq. To 52.8 kg of potassium nitrate).
• 11th and 12th week after transplantation: 44.5 UF / ha or 44.5 kg / ha of potassium (eq. To 96.74 kg of potassium nitrate).
• 13th and 14th week after transplantation: 46 FU / ha or 46 kg / ha of potassium (eq. To 100 kg of potassium nitrate).
• 15th and 16th week after transplantation: 59.7 UF / ha or 59.7 kg / ha of potassium (eq. To 129.78 kg of potassium nitrate).

The potassium nitrate equivalence refers to the potassium fertilizer units, since this fertilizer also contributes nitrogen.

CALCIUM IN THE LETTUCE FERTILIZER

Calcium is another vital element for the development of lettuce. Its lack invites the appearance of tip burn or burns on the edges.

It must be taken into account that water can provide a lot of calcium and other elements, but also with the absorption rule, whereby if the calcium is not at least twice the concentration of magnesium it will not be absorbed.

Calcium is absorbed in the form of a Ca2 + cation and on the market we can find different ways of providing this element. The best known, without a doubt, is calcium nitrate .

• 1st and 2nd week after transplantation: 0.45 UF / ha or 0.45 kg / ha of calcium (eq. To 1.66 kg of calcium nitrate).
• 3rd and 4th week from transplant: 1 FU / ha or 1 kg / ha of calcium (eq. To 3.70 kg of calcium nitrate).
• 5th and 6th week after transplantation: 2 FU / ha or 2 kg / ha of calcium (eq. To 7.4 kg of calcium nitrate).
• 7th and 8th week after transplantation: 4 FU / ha or 4 kg / ha of calcium (eq. To 14.8 kg of calcium nitrate).
• 9th and 10th week after transplantation: 5.5 UF / ha or 5.5 kg / ha of calcium (eq. To 20.3 kg of calcium nitrate).
• 11th and 12th week after transplantation: 8 FU / ha or 8 kg / ha of calcium (eq. To 29.62 kg of calcium nitrate).
• 13th and 14th week after transplantation: 10 FU / ha or 10 kg / ha of calcium (eq. To 37 kg of calcium nitrate).
• 15th and 16th week after transplantation: 12 FU / ha or 12 kg / ha of calcium (eq. To 44.44 kg of calcium nitrate).

MAGNESIUM IN LETTUCE FERTILIZER

Magnesium, like calcium, is also absorbed in ionic form, Mg2 +. It is a very mobile element in the plant but it competes with other cations such as calcium, potassium or sodium.

It is normal that when large amounts of potassium are added to the maturation of a crop, calcium levels drop suddenly.

We are going to see how magnesium is distributed in the plant during all stages of its development.

• 1st and 2nd week after transplantation: 0.2 UF / ha or 0.2 kg / ha of magnesium (eq. To 1.20 kg of magnesium sulfate).
• 3rd and 4th week after transplantation: 0.5 UF / ha or 0.5 kg / ha of magnesium (eq. To 3.01 kg of magnesium sulfate).
• 5th and 6th week after transplantation: 0.7 FU / ha or 0.7 kg / ha of magnesium (eq. To 4.21 kg of magnesium sulfate).
• 7th and 8th week after transplanting: 1.5 UF / ha or 1.5 kg / ha of magnesium (eq. 9.03 kg of magnesium sulfate).
• 9th and 10th week after transplantation: 1.5 UF / ha or 1.5 kg / ha of magnesium (eq to 9.03 kg of magnesium sulfate).
• 11th and 12th week after transplantation: 2.5 UF / ha or 2.5 kg / ha of magnesium (eq. To 15 kg of magnesium sulfate).
• 13th and 14th week after transplantation: 3.5 UF / ha or 3.5 kg / ha of magnesium (eq. To 21.08 kg of magnesium sulfate).
• 15th and 16th week after transplantation: 4.5 UF / ha or 4.5 kg / ha of magnesium (eq. To 27.11 kg of magnesium sulfate).

The data and calculations have been made starting from the Rincon Sánchez bibliographic base.