**4. Discussion**

Sustainable crop production can be defined as the agricultural practices that meet human needs for food, is economically viable, while at the same time being environmentally positive [26]. Evaluation of 62 years data of the classical long term trial has shown the importance of nutrient management on all three aspects of sustainability: (1) Improvement of crop yield, sustainable yield index, WUE and soil fertility to

*Effect of Balanced and Integrated Crop Nutrition on Sustainable Crop Production in a Classical… DOI: http://dx.doi.org/10.5772/intechopen.102682*

produce sufficient food (Social), (2) Profitability of crop production, efficient use of resources, and maintenance of soil fertility to grow the income of farmers (Economic), and (3) Efficient use of nutrients and improving soil fertility to minimize nutrient loss (Economic and Environmental).

#### **4.1 Effect of balanced nutrition on the sustainability of crop production**

The data of the trial confirmed that a balanced nutrition increases crop yield, avoids nutrient deficiency, increases nutrient and water use efficiency, protects the environment by minimizing nutrient loss, and improves soil fertility. Chopra et al. (2014) reported similar results [27]. Application of mineral N + P + K + Mg fertilizer as balanced nutrition resulted in the highest yield and income of crop (**Figure 1**). Similar results were reported for potato with N + P + K + Mg + S application [28] and for maize with N + P + K + Mg application [29, 30] as balanced nutrition compared to treatments of unbalanced nutrition. Omitting nutrients reduced crop yield and resulted in an economic loss of between 89 and 812 \$ha−1 (**Figure 1**). Dev (1998) and Chander et al. (2012) also reported that omitting nutrients significantly decreased yield and profit of maize, millet, rice, soybean, and wheat [14, 31]. Application of only FYM significantly reduced crop yield and income compared to the balanced nutrition (**Figure 1**). Černý et al. and Dilshad et al. (2010) and Abid et al. (2020) reported a significant reduction of barley, maize, potato, rice, and wheat yields with the application of FYM only compared to N + P + K mineral fertilizer [32–34]. Bhattacharyya et al. (2014) reported a decrease in maize and wheat economic benefit at FYM alone compared to N + P + K fertilizer [35].

Crop varieties improved during the 62 years of the trial and resulted increasing yields. Evaluation of the cereal yield per ha indicates that the average yield was increased by 101% during the latest decade (2010–2020) compared to the average yield measured between 1961 and 1970 for Germany [19]. Fertilizer application is an essential management practices that positively affects yield and income in the long-term. The balanced nutrition of the essential plant nutrients was best nutrient management practice and resulted in the highest yield (**Figures 4** and **5**). Crop yield and income increased during the years 2008 to 2020 were 66% and 1901\$ha−1higher than in the earliest years 1958 to1968 (**Figures 4** and **5**). The combined effects of better varieties and fertilizer application improved crop yield and soil fertility during the trial periods (**Figures 2, 3** and **9**). An unbalanced nutrition resulted in yield loss of 6 to 53% or up to 311\$ha−1 during the earliest decade, but 8 to 69% (158 to 3075\$ha−1) loss during the latest decade. N fertilizer application without PK fertilizer similarly resulted in 86% reduction of maize grain yield during 2001–2006 compared to maize yield at N without PK fertilizer during 1987–1988, because cumulative K releasing power of the soil has depleted 33% in 2003 compared to K releasing power of the soil in 1986 [36]. The high productivity and revenue per area with the balanced nutrition support the social and economic aspects of sustainable crop production.

The long-term application of balanced nutrient positively affects the stability of crop yield [37]. Balanced nutrition (N + P + K + Mg fertilizer) resulted in the highest SYI compared to omitting nutrients (**Figure 6**). Ray et al. (2017) similarly reported the highest SYI with the balanced nutrition (N + P + K + S + Zn fertilizer) compared to the unbalanced nutrition [38]. Application of only FYM decreased SYI by 8% compared to both the N + P + K and N + P + K + Mg treatments (**Figure 6**). Abid et al. (2020), Bhattacharyya et al. (2014), and Malarkodi et al. (2019) reported a reduction of SYI, respectively by 6%, 17% and 5% with only FYM compared to N + P + K

mineral fertilizer [34, 35, 39]. The highest SYI was observed at the balanced nutrition and it confirms stable yields as an indicator of sustainability.

Land, solar energy, and water are the major natural resources required to produce crop. Efficient utilization of these resources is necessary for sustainable crop production. Nutrient application is important to increase land and water use efficiency. Reduction of yield because of unbalanced nutrition (**Figure 1**) resulted in inefficient use of land, because more land (1.1 to 1.7 ha) is required to achieve the same yield as on 1 ha of land at the balanced nutrition treatment. The N + P + K + Mg fertilizer resulted in the highest WUE compared to omitting nutrients and FYM application alone (**Figure 6**). Omitting nutrients decreased WUE by 7 to 63%. Chander et al. (2013), Suhas et al. (2013) and Chander et al. (2012) reported similar results [6, 8, 31]. Efficient use of resources is only possible in a balanced application of plant nutrients.

The best practice of nutrient management increases nutrient use efficiency in crop production. The N, P, and K use efficiencies (NUE, PUE, and KUE) of major cereal crops are reported to be between 40 and 65%, 15–25%, and 30–50% respectively at recommended management practices with recommended soil P and K contents [40]. The balanced nutrition (N + P + K + Mg fertilizer) resulted in a high nutrient use efficiency compared to the unbalanced nutrition. The average NUE, PUE, and KUE of crop at the balanced nutrition were, respectively 77%, 49% and 84% (**Figure 7**). Omission of nutrients and application of only FYM decreased nutrient use efficiency by 5–56%, because crop growth and yield were limited by nutrient deficiency. Kumar et al. (2021) reported reduction of nutrient use efficiency by 27–65% for potatoes due to nutrient omission compared to the balanced nutrition [41]. Similar results were reported in Wang et al. (2010) for maize and wheat [42]. Inefficient use of nutrients causes a high cost of production or economic loss and a high risk of environmental pollution.

Physical, chemical, and biological parameters of soil fertility influence the capacity of soil to support crop growth. Nutrient management with its direct impact on nutrient and organic matter contents, pH, and cation exchange capacity of soil supports sustainable crop production. Long-term soil fertility is ensured by balanced nutrition and concurrent application of lime [43]. Omitting P fertilizer decreased soil P content (**Figure 3**). Bhattacharyya et al. (2015) also reported a reduction of soil P content due to P fertilizer omission [44]. K removal without replacement depleted soil K from the medium to the low level (**Figure 2**). Zhao et al. (2014) reported that omitting K fertilizer similarly decreased soil K content at different depths [45]. Balanced nutrition improved soil nutrient content to desirable levels and increased yield with positive impacts on sustainable crop production.

The soil organic matter improves soil water-holding, aeration, nutrient absorption and release, and minimization of leaching and erosion [46]. Application of mineral fertilizer and FYM alone slightly increased soil organic carbon (SOC) compared to the treatment without any fertilizer (**Figure 8**). This was also found by Aula et al. (2016), they reported a significant increase in SOC through the application of NP and NPK fertilizers and FYM compared to without any fertilizer [47]. The only slight increase of organic matter at the application of mineral fertilizer and FYM alone was caused only by root residues (**Figure 1**), because crop residues were removed from the field for more than 50 years. Zhao et al. (2014) reported a significant increase of SOC at mineral NP and NPK fertilizers plus wheat straw compared to NP and NPK fertilizers without straw [45]. The unbalanced nutrition depleted soil organic matter content through a low crop yield. The balanced nutrition improves soil organic matter with positive implications on soil fertility supporting crop growth and yield directly related to sustainable crop production.

#### **4.2 Effect of integrated crop nutrition on the sustainability of crop production**

The integrated crop nutrition as the combination of organic and mineral fertilizer contributes: (1) to maintain or enhance soil fertility, (2) to improve nutrient stocks in the soil, and (3) to reduce nutrient loss to the environment by increasing nutrient use efficiency [48]. It improves the availability of nutrient and corrects nutrient imbalances to increase crop yield. Application of FYM plus mineral fertilizers significantly increased crop yield compared to FYM alone (**Figure 10**), which was also reported by Abid et al. (2020) and Mahmood et al. (2017) for maize yield [34, 49] and by Baniuniene and Zekaite (2008) for potato yield [50]. FYM without mineral fertilizer reduced crop yield by 44% and 492\$ha−1 (**Figure 10**). Bhattacharyya et al. (2014) similarly reported 47% yield and 59% profit reductions for maize and 49% and 52% for wheat at only FYM application compared to FYM plus NPK fertilizer [35]. The integration of FYM with mineral fertilizer increased yield and income, because it improved nutrient availability required to support the healthy growth of crops.

Integrated nutrition was the best nutrient management practice, because it increased crop yield and income to the highest level (**Figures 10**–**12**) and it improved soil fertility (**Figures 15–17**). Vasuki et al. (2009) similarly reported that the integrated and balanced use of mineral fertilizer plus organic manures have maintained an increase of crop yield at a higher level over the years [36]. Application of only FYM resulted in a loss of income of 1347 \$ha−1 in the latest years (2008–2020) compared to 237 \$ha−1 in the earliest years (1958–1968) of the trial, as compared to the treatment of FYM with NK fertilizer during the respective time intervals (**Figure 12**). Hejcman and Kunzova (2010) similarly reported that wheat yield reduction due to application of FYM only was high during the latest decade (1997–2006) and low during the earliest decade (1957–1966) compared to yield at integrating FYM with NPK fertilizer [51]. The synergy between improved varieties and integrated nutrition sustained the increasing yield and income during the long-term, because nutrients have been available in quantity and ratio demanded by high-yielding crop varieties.

The SYI is viewed as a quantitative measurement of sustainability. A high SYI with minimum standard deviation indicates low variability of yield. Integrated nutrition increased SYI compared to the application of FYM alone (**Figure 13**). Integrating FYM with NPK fertilizer similarly increased SYI of maize [34] and sunflower [39] compared to only FYM treatment. Low SYI at only FYM application shows a high variability of yield, while the high SYI at the integrated nutrition indicates sustainable crop production.

Natural resource use efficiency of crop production is increased by improving crop growth. Best nutrient management is therefore needed to achieve efficient utilization of land and water for crop production. Application of only FYM resulted in inefficient land use, because crop yield was 44% lower than at the integrated nutrition (**Figure 10**). Therefore, it requires 1.4 ha of land to achieve the same yield as with FYM plus NP fertilizer on 1 ha, and it decreased WUE by 40% (**Figure 13**). Dubey et al. (2014) similarly reported a 9% reduction of WUE of the crop at only FYM application compared to FYM plus NPK fertilizer [52]. Improvement of land and water use efficiency is an important contribution to sustainable crop production.

Efficient use of nutrients applied as organic plus mineral fertilizers reduces nutrient losses, protects the environment and improves economic return on investment in fertilizer. It was confirmed in the trial data as the highest percentage of crop NUE, PUE, and KUE were achieved with integrated nutrition. Application of only FYM decreased nutrient use efficiency by 15–24% compared to integrated nutrition (**Figure 14**). Abid et al. (2020) similarly reported a 36% reduction of nutrient use efficiency of maize [34] and Bhattacharyya et al. (2014) reported a 24% and 23% reduction for maize and wheat [35] at only FYM compared to integrating FYM with NPK fertilizer. Application of only FYM was resulted in inadequate and unbalanced availability of nutrients, so that it has been caused a reduction of crop growth and yield, which were ultimately leading to low recovery and inefficient use of nutrients.

Nutrient management improves nutrient availability in the soil and supports soil fertility via its impact on nutrient content, soil organic matter and pH. Integrating FYM with P fertilizer increased soil P2O5 content compared to only FYM (**Figure 15**). Malarkodi et al. (2019) and Hejcman and Kunzova (2010) reported similar results [39, 51]. FYM plus K fertilizer-maintained soil K2O content within the medium range, but only FYM and FYM + NP fertilizer decreased soil K2O to the 'low' level compared to the initial soil K2O (**Figure 16**). Application of only FYM similarly depleted soil K2O compared to FYM plus K fertilizer [39, 49]. Integrated nutrition improved soil nutrient content and increased crop production as an indicator of efficient use of input and resources with positive implications on sustainability.

Some authors claim that the production of cereal crops have stagnated or declined in recent years due to unbalanced and inadequate nutrient application and degradation of the soil organic matter [27]. The decomposition of organic matter releases the nutrients necessary to increase crop yield. Integrated nutrition increased soil organic carbon (SOC) compared to the application of FYM alone (**Figure 17**). A similar result was reported in Malarkodi et al. (2019) and Hejcman and Kunzova (2010) [39, 51]. An increase in SOC indicates organic matter improvement that makes soil condition favorable to increase yield and to sequestrate carbon in crop residues.

The soil pH regulates solubility and availability of nutrients. It increased rapidly during 1958–1998 at integrated nutrition compared to FYM alone by CaO (lime) application (**Figure 18**). Abid et al. (2020) similarly reported that supplementing FYM with NPK fertilizer significantly increased soil pH compared to only FYM [34]. Since 1998, the soil pH was maintained at a desirable level with a slight difference between treatments due to the accumulated effect of lime.
