**2. Materials and methods**

#### **2.1 Location and history**

The Hanninghof LTT is one of few classical LTT in the world. It is located near Duelmen in Western Germany. Crop rotation started with potato cultivation in 1958, followed by winter rye in 1959 and oat in 1960. The sequence of rotation changed to silage maize, winter rye, and potato after 2008 to adjust the trial to current agricultural practices, but the basic setup of the trial remains the same. During 1958–2020, potato, winter rye, oat, and silage maize were cultivated respectively 19, 21, 17, and 5 times.

#### **2.2 Soil and climate**

The trial was established on a loamy sandy soil with the following initial soil parameters: P2O5 13.3 mg (100 g) –1, K2O 10 mg (100 g) –1, Mg 2.1 mg (100 g) −1, organic carbon 2.1%, N total 0.1%, and pH 5 at soil depth 0–30 cm. The annual rainfall and yearly mean air temperature were, respectively 469–1273 mm and 7.7–12.3°C during 1958–2020.

#### **2.3 Layout**

The trial is a two-factorial experiment in a split-plot with a randomized complete block design. The cultivated area of the trial is 0.3 ha (72 m × 42 m). The field is split into two parts, one receiving FYM every 3 years during 1958–2008 and yearly since 2009 and the other part is without FYM. Each of the two parts is subdivided into 32 plots, i.e., 64 plots in total. The gross area of a plot is 4.5 m × 10.5 m with a harvested area of 3.5 m × 9.5 m to avoid the border effect.

#### **2.4 Treatment**

Sixteen treatments were established as shown in **Table 1**. Each treatment is replicated four times and randomly assigned to plots. In 1960, a treatment with N only (#8 and #16) was established. Since the trial was already ongoing for 2 years, new control treatments were assigned. The new control treatments (#7 and #15) are omitted from data evaluation (**Table 1**), because they were not different from treatments #2 and #10.


#### **Table 1.**

*Description of treatments.*

### **2.5 Nutrient application**

Mineral fertilizer nitrogen (N), phosphorous (P), potassium (K), and magnesium (Mg) rates were the same for the treatments with and without FYM during 1958–2008. FYM was applied as pig manure at a rate of 25 t ha−1 once every 3 years in spring. Nutrient content of FYM is calculated based on 7 kg N-total, 6.7 kg P2O5, 7.2 kg K2O and 2.2 kg MgO per ton of pig manure [17].

After 2008, the trial was adjusted to reflect recent crop rotation and nutrient application. Oat was replaced by silage maize. FYM was replaced by cattle slurry and applied annually at the rate of 30, 20, and 20 m3 ha−1, respectively during silage maize, winter rye, and potato cultivation. The nutrient content of FYM was considered in the total nutrient application rate to make the nutrient input with FYM and without FYM comparable. The nutrient content of cattle slurry was analyzed every year in the laboratory. Nutrient rates for potato, winter rye, oat and silage maize are given in **Table 2**.

N, P, K, and Mg from mineral fertilizers were applied as calcium ammonium nitrate (CAN) with 4% MgO, triple supper phosphate, potassium chloride, and magnesium nitrate respectively. Since 2013, N was applied as CAN with 6% S to avoid 4% MgO content of CAN that resulted in a reduction of the treatment effect of Mg on crop yield. Since 1958, lime (CaO) was applied to the whole field at a rate of 1000 kg ha−1 every 3 years to stabilize soil pH. Since 2009, S fertilizer was applied every year at a rate of 20 kg S per ha on the whole field to avoid S deficiency. Pig manure was applied 10 days before potato planting during 1958–2008. Since 2009, cattle slurry was applied 10 days before silage maize and potato planting, and at the early vegetative stage of winter rye. Mineral fertilizer N was applied once at planting for potato. It was split applied for winter rye at early vegetative, stem elongation, and booting; for oat at seeding and booting; and for maize at seeding and early vegetative growth stages. P, K and Mg mineral fertilizers were applied once at the planting of potato, oat, and silage maize; and at the early vegetative stage of winter rye cultivation.

#### **2.6 Analysis of crop and soil parameters**

Crop fresh and dry matter yields were recorded. The crop samples were dried in a drying cabinet at 70°C. Soil samples were collected before crop seeding (planting) at

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


#### **Table 2.**

*Nutrient application rate per year during 1958–2020.*

0–30 cm soil depth from all 4 plots of each treatment and mixed thoroughly to obtain a uniform sample. Macro and micro nutrient concentrations in the tuber, grain, straw and silage of crop and soil nutrient content, organic matter and pH were analyzed as follows:

N content of crop: Crop dry matter was digested with sulfuric acid and catalyst tablet to produce 50 ml of filtered samples. The N concentration of the sample was determined by continuous flow analysis based on standard operation procedures according to the Kjeldahl method.

Macro and micro nutrients content of crop: The dried crop samples were digested with nitric acid by direct heating in the microwave. The macro and micro nutrient in the digested samples were determined on the ICP-OES (inductively coupled plasmaoptical emission spectrometry) according to standard operation procedures.

Soil P and K content: The air-dry soil samples were sieved via 2 mm sieve and mixed with 100 ml calcium acetate and lactate solutions and shaken on the flat shaker for 90 minutes. The plant available P and K contents of filtrate of the soil samples were determined by ICP.

Soil organic matter: The total organic carbon (TOC) was determined by Vario Select Elementary device. The TOC content was calculated from the integral values of the measurement peaks and the calibration coefficients.

Soil pH: The air-dried soil samples were sieved on 2 mm sieve and pH was measured in a 0.01molar CaCl2 solution after 1 hour by pH electrode.

#### **2.7 Data organization and evaluation**

Crop yield data were converted to cereal units to aggregate data of different crops along 62 years. The potato tuber, winter rye grain, oat grain, and maize silage yield were multiplied by respectively 0.22, 1.01, 0.85, and 0.18 to convert into cereal unit [18]. The significance differences between average crop yield of treatments were analyzed statistically. The yield data were grouped into 12 periods (1958–1963, 1963–1968, 1968–1973, 1973–1978, 1978–1983, 1983–1988, 1988–1993, 1993–1998, 1998–2003, 2003–2008, 2008–2014, and 2014–2020) to evaluate the trend of crop yield, because crop varieties remained unchanged during 5- or 6-years interval per each period with similar effect on yield.

Crop yields data (1958–2020) were converted to revenue (economic yield) by multiplying annual yields with historical crop prices [19]. The cost of mineral fertilizer was obtained by multiplying the mineral fertilizer rate with historical prices [20]. FYM was regarded free of cost. The economic evaluation included mineral fertilizers cost only, because all other costs of crop production were considered equal for all treatments. Economic benefit (USDha−1) = crop revenue - mineral fertilizer cost.

Sustainable yield index (SYI) was calculated according to Singh et al. (1990) based on the standard deviation of mean to evaluate the stability of yield [21, 22]. SYI = average yield (AY) of treatments minus standard deviation (SD) divided by maximum yield (MY) in different years and treatments.

Green water use efficiency (WUE) was calculated according to Sharma et al. (2013) based on historical rainfall data recorded at the LTT site [23]. WUE (kg yield per mm rainwater) = Yield (kgha−1) divided by cumulative rainfall (mm) from sowing to harvest.

Nutrient use efficiency was calculated according to partial factor productivity [24]. N use efficiency (%) = N removal with N fertilized crop divided by N fertilizer rate and multiplied by 100. The calculation was done similarly for P and K fertilizer use efficiencies.

The soil fertility is measured by nutrient content, organic matter and pH. The soil parameters were organized with a three-year moving average. The changes in soil fertility were evaluated in comparison to the control treatments and initial values measured in 1958.
