4-Nutrient Management

Transcript

Friends, we are in the third week of our CASI course and now we will look at the nutrient management of soil. We already know that plant growth is not possible without nutrients. We define nutrients as those elements without which plants cannot grow completely. We can overcome the deficiency of these nutrient elements only through the use of these elements. These nutrients take part in the metabolism of the plant and also aid in their development.

We already know that plants need 17 nutrients for its growth. Out of these 17 nutrients, carbon, hydrogen and oxygen are available in the environment. We divide the rest of nutrients into two types; major elements and micro elements.

The nutrients that come under major elements include nitrogen, phosphorus, potash, calcium, magnesium and Sulphur. Micro nutrients include copper, iron, manganese, molybdenum, boron and others. We call them major and minor elements because plants require major elements more than the minor elements.

Now, we will look at why nutrients are important for a plant and what are the symptoms of its deficiency.

Nitrogen is important for plants as it gives greenness to the plants and aids in its growth. Before talking about the deficiency of nutrients and plants, we will discuss the mobility of nutrients.

The elements within a plant are either mobile or immobile. The major elements within a plant are nitrogen, phosphorus and potash and they are considered mobile. A common way of finding deficiency symptoms within a plant are by looking at the greenness of the leaves. The mobile elements within a plant can move quickly. So their deficiency is more common in older leaves. The deficiency of immovable elements is more common in new leaves.

Now let us talk about nitrogen. Due to nitrogen deficiency, the leaves of a plant turn yellow and their yellowness keeps increasing as long as the nitrogen deficiency persists. As a result, these leaves fall and this affects the plant.

Now, phosphorus deficiency is the opposite of nitrogen deficiency. In phosphorus deficiency, the leaves turn deep green as compared to yellow in nitrogen deficiency. As the leaves turn deep green due to phosphorus deficiency, a purple tint appears in the leaves and this purple tint sometimes appears in the stalk of the plant.

In Potash deficiency, the plant turns yellow especially in the margins and tip. If the deficiency continues then eventually the plant dries up.

Sometimes due to phosphorus deficiency, the growth of plants increases suddenly but at the same time they become weak and eventually fall down.

So these were the deficiency of three major elements. Similar to these is the deficiency of Sulphur and its deficiency symptoms are very similar to the deficiency symptoms of nitrogen. But Sulphur deficiency first appears in the new leaves as compared to nitrogen deficiency which first appears on older leaves.

Now we will look at some decision tools through which we can meet the nitrogen needs in plants.

The first is the leaf color chart which is a scale that has 5 or 6 green color strips. These strips go from yellowish green to deep green. Now when we go to our farm, we compare the color of the leaves with this chart. If out of 10 leaves, 6 leaves appear slightly yellow and the greenness of these leaves are less than number 4 on the color chart then we provide per acre 25 kg nitrogen to the farm.

Normally, to identify the nitrogen status in the plants, we repeatedly use the leaf color chart at specific intervals be it a period of 7 to 14 days.

We usually do this till 14 days after sowing but we stop using the leaf color chart after flowering.

This helps us to avoid excess use of nitrogen and increases the usage efficiency of nitrogen and crop productivity.

Green seeker is another decision tool. It is a sensor based equipment that is used to help effectively and precisely to manage crop inputs. We can know the health of the plant through the Green Seeker. There is a sensor fitted at the bottom with a trigger. When we pull the trigger and go to the row of the plant, it keeps giving us a reading for as long as we have pulled the trigger. The reading is measured in terms of NDVI and ranges from 0.00 to 0.99 with a higher NDVI value signifying better health of the plant.

The Green seeker helps us to prevent excess use of nitrogen. We are able to provide the right amount of nitrogen which is required by the plant. We can also connect the green seeker with a smartphone and through an app calculate the nitrogen requirement.

Usually, we use the green seeker in places where we do not have soil testing facilities and thus prevent excess use of nitrogen.

Now we look at the crop manager. It is based on 4Rs which means right source of fertilizer, right time of application, right placement and right application. Crop manager is software based and is mostly used in places where we do not have the facility of soil testing or it is very expensive to do soil testing. In crop manager, we use the knowledge of farmers and feed the personalized data of their farms. We fix a crop productivity target and then based on this target we feed the data which gives us a result where it tells us how much nutrient to apply in this crop. This software helps us to prevent the excess use of nitrogen in our farm and we depend on research trials and demonstrations at farmers’ fields.

So all these decisions tools help us to prevent the excessive use of nitrogen.This is more important in India’s context as nitrogen fertilizer is subsided in the country and the government has to bear a huge economic cost. So if we use all these decision tools like crop manager, green seeker and leaf color chart then we can use fertilizer at the right time, the right form and the right quantity.