Remote Sensing: Useful Approach for Crop Nitrogen Management and Sustainable Agriculture

*Salima Yousfi, José Fernando Marin Peira, Gregorio Rincón De La Horra and Pedro V. Mauri Ablanque*

### **Abstract**

Soil fertility is among the most important criteria that affect crop yield and quality. Nitrogen stress due to the low soil fertility and the lack of nitrogen availability is a major factor limiting the crop productivity in arid and semiarid environments, where fertilization is not optimized in terms of timing and quantity. Managing nitrogen fertilization is one of the most important criteria in the precision agriculture, which helps to improve crop production, environment conditions, and farmer's economy. It is very important to apply N fertilizers with efficient methods allowing to the nutrient use efficiency and avoiding nitrogen losses and environment contamination. Nowadays, remote sensing methods using spectral and thermal approaches have been proposed as potential indicators to rapid identification of crop nitrogen status by providing information about vegetation canopy properties across large areas. The use of remote sensing methods to schedule nitrogen fertilization can help farmers to practice a more sustainable agriculture, minimizing risks of losing the harvest by providing an adequate rate of nitrogen when the crops' needs and at a specific location.

**Keywords:** nitrogen fertilization, remote sensing, smart N management, farmer's decisions, precision agriculture, sustainable agriculture

#### **1. Introduction**

Soil nitrogen amount is among the most important criteria that affect crop yields and quality. Plant growth and development need nitrogen in greater quantity, since it is involved in various physiological processes. Nitrogen is a part of many components of plant cells, including amino acids, nucleic acids [1], proteins, and chlorophyll in plant leaves. Likewise, nitrogen availability produces rapid and early crops' growth, increases protein content of crops, facilitates the uptake and utilization of other nutrients as potassium and phosphorous, improves fruit quality, and controls overall growth of plant [2, 3]. However, nitrogen deficiency rapidly inhibits the growth of plants and alters many metabolic processes. The lack of nitrogen decreases photosynthesis [4], causes appearances of chlorosis [5], reduces chloroplast size [6], and provokes a high decrease in crop quality and yields.

Consequently, analyzing nitrogen amount in soil and crops and the application of N fertilizer in the event of a deficit are essential to improve crop production.

**314**

*Sustainable Crop Production*

Nolit; 1989

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[3] Booij R, Kreuzer ADH, Smit AL, Van der Werf A. Effect of nitrogen availability on dry matter production, nitrogen uptake and light interception of Brssels sprouts and leeks. Netherlands A key factor in the efficiency of nitrogen application is to adjust N input to N crop demand [7]. The addition of N fertilizer when crops' needs, with the right dose, may increase yields and reduce the farmer's input costs. In this way, precision agriculture permits the distribution of the correct quantity of agricultural inputs (fertilization and water irrigation) in real time and at a specific location. Mulla and Schepers [8] reported that precision agriculture aims to improve site-specific agricultural decision-making through collection and analysis of data, formulation of site-specific management recommendations, and implementation of management practices to correct the factors that limit crop growth, productivity, and quality. Moreover, Gebbers and Adamchuk [9] described the precision agriculture as a key to optimize the use of available resources to increase the profitability and sustainability of agricultural operations, to reduce negative environmental impact, and to improve the quality of the work environment and the social aspects of farming.

Therefore, monitoring nitrogen fertilization with a high coverture of crop, high spatial variability, and right timing of applications are very important to improve crop's production and to help farmers to take decisions. Nowadays, crop water and nitrogen managements use many indices acquired by remote sensing techniques. Mulla and Miao [10] informed that proximal sensing of crops is currently the primary tool used to detect nutrient deficiencies for variable rate application of fertilizer. This is based on researches that showed nitrogen deficiencies could be detected using spectral reflectance in the green, red, red edge, and near-infrared portions of the spectrum.

In this chapter, we explain the usefulness of the use of remote sensing techniques in precision agriculture in managing nitrogen fertilization. Remote sensing methods are rapid and nondestructive ways of permitting multiple optical measurement indicators of plant greenness and crop nitrogen status. Fox and Walthall and Hunt et al. [11, 12] showed that the greenness of plants is strongly related to leaf chlorophyll content and to N status, and so it has been used as an indicator of N availability. Moreover, remote sensing techniques can be generally defined as doing the right management practices at the right location, in the right rate, and at the right time [10]. This would reduce surplus N in the crop production system without reducing crop yield, which would in turn reduce N losses to surface and groundwaters [13].
