**1. Introduction**

Long term trials (LTTs) are conducted on a stationary site for many years and classified as Young, Medium, and Classical, respectively in age less than 20, 20–50, and older than 50 years [1, 2]. They are appropriate to study the sustainability of crop production which is defined as the ability to produce the required crop yield and quality to satisfy present and future food demand, while protecting the environment. Population and economic growths are estimated to result in a 50% increase in the demand for food by 2050 with little scope to expand the agricultural area [3]. Thus, a sustainable increase of crop yield per area is required to meet the rising demand for food.

This target requires improvement of yield through integration of productive crop varieties, fertile soils, adequate water supply, sufficient plant nutrients with efficient use, protection of crops against weeds, diseases and pests, and post-harvest care [4]. Continuous crop yield increases are mostly determined by the improvement of crop varieties. Improved crop varieties require advanced cultivation practices, best nutrient application strategies, and pre- and post-harvest crop protection [5]. Improvement of crop nutrition is one of the essential management factors to increase yield.

A trial conducted in India for example, showed that improved cultivars along with balanced nutrition resulted the highest yield increase in range of 92 to 204% over the farmer's practice [6]. Vyn (2014) said "global maize yields will not be able to continually boost to achieve food security without providing adequate and balanced nutrients" [7]. The synergy between improved genetic and adequate nutrient supply sustained the increased production of rice and wheat for nearly three decades in India; however, in recent years the high productivity is stagnating or declining in spite of supplying increased N, P and K fertilizer rates, because of unbalanced nutrient application [8].

Soil fertility is the major environmental factor and is viewed as the capacity of the soil to retain, cycle, and supply essential nutrients to support crop growth for a long time [9]. The relationship of nutrient application and soil fertility is reliably studied in the LTTs, because soil fertility develops gradually and therefore, evaluation of its effect on crop production requires monitoring over a long time and a proper documentation of data [10]. The LTTs are the right tool to study changes that can take decades before they become visible, for example: trends of crop yield and effects of the environment on agriculture or vice versa [11]. Since agriculture is removing nutrients from the soil an efficient replacement of nutrients back into the soil is required to sustain crop yields [12]. The target to increase crop yield per area requires avoiding nutrient mining, maintaining soil fertility, and minimizing nutrient loss to protect the environment.

Balanced nutrition is the key to sustainable crop production and maintenance of soil health with both economic and environmental benefits. An unbalanced nutrition results in a low nutrient use efficiency, poor economic returns, and high environmental pollution [13]. The Law of the Minimum states: "If one of the essential growth factors/nutrient is deficient, plant growth will be limited even when all other factors/ nutrient are sufficiently available that growth is improved by the application of deficient factor/nutrient". Dev (1998) viewed the balanced nutrition as "a best management practice refer to the application of essential nutrients in optimum quantity and proportion including proper application methods and time for the specific soil, crop, and climate conditions" [14]. It ensures accessibility of crops to an adequate nutrient supply at every growth stage to avoid over or under-supply enabling the crop for a strong, healthy and productive growth while minimizing pollution of the environment [15]. It can be further defined as the application of right sources of nutrients in an adequate amount and ratio with optimum methods at the time required to support healthy crop growth to increase yield and quality.

Integrated crop nutrition is the combined application of organic and mineral fertilizers to increase yield and to improve soil fertility. Organic fertilizer alone can often not fully satisfy the nutritional demand of crops, because it contains inadequate *Effect of Balanced and Integrated Crop Nutrition on Sustainable Crop Production in a Classical… DOI: http://dx.doi.org/10.5772/intechopen.102682*

and unbalanced nutrients [16]. It may not be available in sufficient quantities. Supplementing organic fertilizer with mineral fertilizer is needed to improve nutrient availability and increase crop yield.

The Hanninghof classical LTT was established in 1958. Three strategies of crop nutrition are compared: (1) Balanced nutrition, (2) Integrated nutrition, the combination of farmyard manure (FYM) with mineral fertilizer, and (3) Organic nutrition, application of FYM only. The effects of these different treatments on crop yield, economic revenue, sustainable yield index, water and nutrient use efficiencies and soil nutrient content, organic matter and pH are measured to evaluate social, economic, and environmental benefits of best strategies of nutrient application. The objective of the trial is to study the long-term impacts of different nutrient management on parameters of crop productivity and soil fertility to quantify sustainable crop production.
