Yield and cost-effectiveness of alfalfa hay production as dependent on fertilization

Alfalfa is the most important forage crop in Serbia grown for high yields of quality fodder. In order to expand alfalfa production on pseudogleys, research was conducted in the vicinity of Kraljevo. Results suggest the potential for growing alfalfa on acid soils in Serbia. The combined use of 2.5 t ha and 5 t ha lime and 30 t ha manure on the pseudogley increases the soil pH, humus content and available phosphorus and potassium levels, while decreasing the content of mobile aluminum, thus making the soil suitable for alfalfa production and high biomass yields (115.9 t ha) during 3-4 years of stand utilization.


Introduction
Alfalfa as a forage crop is highly adapted to a range of soil and climatic conditions in Serbia.It is grown on about 200,000 ha, giving an average hay yield of 5.7 t ha -1 (SGS, 2011).However, the use of modern cultivars, fertilization, irrigation, weed, pest and disease control, proper utilization and cutting frequency 156 can lead to hay yields of 16-20 t ha -1 during 4-5 years (Katić et al., 2010).Success in the production of high-quality alfalfa hay rich in proteins and minerals requires the use of appropriate cultural practices.Ensuring adequate nutrient supply through fertilization is a major technology-related factor in profitable alfalfa production (Lanyon and Griffith, 1988).
The first step preceding fertilization during stand establishment is soil analysis to evaluate the fertility status of soil and plan a nutrient management program.It is imperative to keep in mind that alfalfa harvest removes large amounts of nutrients from the soil, with 12 kg phosphorus and 25 kg potassium required per ton of dry matter (Đukić et al., 2009).Since alfalfa uptakes nitrogen from the atmosphere, low application rates of nitrogen fertilizers are recommended (30-50 kg ha -1 ) during alfalfa stand establishment.Zinc, iron, copper, manganese and boron deficiencies rarely occur in soils in Serbia.Prior to micronutrient fertilization, soil or plant tissue should be tested for nutrient deficiencies (Katić et al., 2013).Calcium and magnesium deficiencies are rare in soils used for alfalfa production.However, acid soils require the use of lime materials for successful alfalfa production (Katić et al., 2009).Liming as an ameliorative intervention increases soil pH i.e. reduces soil acidity, thus leading to an increase in readily available phosphorus and potassium levels (Dugalić et al., 2011).
The use of liming materials is an essential practice in reducing Al, Fe and Mn concentrations to levels that are not harmful to crops (Bošković-Rakočević andBokan, 2005, Dugalić et al., 2008;Dugalić et al., 2011).

Materials and methods
In order to analyze the yield and stand life of alfalfa on a pseudogley, field trials were established at two locations, viz. at the experimental field of the Secondary School of Agriculture, Kraljevo, in 2004Kraljevo, in -2007, involving liming at two rates 3 t ha -1 and 6 t ha -1 as the main treatment (Katić et al., 2009), and at Dragčići in the Kraljevo region in 2009, involving 5 treatments: I) control (without liming); II) 2.5 t ha -1 lime; III) 5 t ha -1 lime; IV) 2.5 t ha -1 lime + 30 t ha -1 manure and V) 5.0 t ha -1 lime + 30 t ha -1 manure.Primary tillage in the autumn of 2008 involved fertilization with 500 kg NPK 16:16:16 fertilizer i.e. 80 kg NPK/ha.The acid psuedogley of the Kraljevo valley is characterized by high levels of Al 3+ ions (24.8 mg/kg) and Mn 2+ ions (46.4 mg/kg) (Dugalić et al., 2008).Detailed soil chemical analyses, physical and mechanical properties of the soil and trial set-up techniques were described by Katić et al. (2009), Dugalić et al. (2011) and Bokan et al. (2010).Soil analysis (Tab. 1) at both locations shows similarity in chemical composition at 0-30 cm depth, except in available phosphorus levels which are 4.5 mg/100g dry soil lower at Dragčići.

Results and Discussion
On the pseudogley in Kraljevo, during 2004-2007, the treatment with 3 t ha -1 of lime resulted in yields of 180.4 t ha -1 of green fodder or 44.4 t of hay ha -1 , while liming at a rate of 6 t ha -1 gave respective yields of 199.2 t ha -1 and 50,4 t ha -1 (Tab.3).These yields are high and similar to those on neutral fertile soil (Katić et al., 2010).Liming extended the alfalfa stand life to 4 years and ensured yield stability during the year (Katić et al., 2009).Yield differences between the lime application rates were significant in the third and fourth years of plant life, and the analysis of economic effects in alfalfa hay production with liming included indicates an economic return (Katić et al., 2009).At the Dragčići location, on a fine-textured pseudogley, liming at 2.5 t ha -1 during 2009-2011 gave high yields of green forage -84.4 t ha -1 (Tab.3) or about 16 t ha -1 i.e. 5.6 t ha -1 of hay annually, which is the average hay yield in Serbia (SGS 2011).The treatment with 5 t of lime ha -1 resulted in higher yields of green forage (101.3 t ha -1 ) and hay (20.3 t ha -1 ), giving an annual yield of 6.7 t ha -1 .However, alfalfa yields were the highest after the combined treatment with mineral fertilizers, lime and manure.The application rates of 2.5 t ha -1 for lime and 30 t ha -1 for manure gave forage yields of 111.8 t ha -1 or hay yields of 22.4 t ha -1 , with an average annual hay yield of about 7.5 t ha -1 .158 Liming at the higher application rate (5 t ha -1 ) combined with 30 t of manure ha -1 gave green forage and hay yields of 115.9 t ha -1 and 23 t ha -1 , respectively, over the three-year period or an annual hay yield of 7.7 t ha -1 .No statistically significant differences were observed in green forage yield between low lime application rate + manure and high liming rate + manure treatments (Tab.3).(Dugalić et al., 2011).Successful alfalfa production requires the use of liming materials to increase the levels of readily available P 2 O 5 , K 2 O, Ca and Mg (Tab 4.) and decrease the availability of Al, Fe Mn and Zn (Dugalić et al., 2008).
Growing alfalfa on the soil treated with lime (3 and 6 t ha -1 ) led to an increase in P content in the plant from 0.281 % to 0.395 % and 0.456, respectively (Tab.4).Moreover, potassium levels in the plant increased from 1.99 % to 2.34 % and 3.05%, respectively, simultaneously with an increase in Ca content, while Fe, Mn and Zn levels decreased.Katić et al. (2013) provide soil P and K threshold values as a basis for alfalfa fertilization during stand establishment and utilization.Threshold values on soil nutrient contents should be set in the future to enable proper use of fertilizers based on nutrient removal by the alfalfa crop.
Nutrient requirements for alfalfa plants were analyzed using data from Canada, Government of Manitoba (2006).The comparison of the results in the present study with the threshold values suggests that sufficient N, P and K levels were supplied by both lime application rates (Tab.5).The content of sulfur was not determined since soils in Serbia exhibit no sulfur deficiencies.Furthermore, the contents of Ca, Fe, Mn and Zn were also found to be adequate for alfalfa plants.Mg content in the lime treatment at 3 t ha -1 was close to marginal and sufficient (Tab.5).The levels of the micronutrients B, Mo and Cu were not determined, but they should be covered by further research, given their importance for alfalfa.
The analysis of the economic effects of mineral fertilization and liming in alfalfa hay production shows that the highest price of hay was in the first year (RSD 34.0) due to the highest costs associated with stand establishment (Katić et al., 161 2013).Lower hay prices were observed in the second and third years of stand utilization (RSD 5.7 and 9.7, respectively).The average price of 1 kg hay for the 2009-2011 period at the Dragčići location was RSD 12.8.This price should be considered in planning the use of hay on either one's own farm or for the market.It the market price approaches the price of hay produced, production costs should be reduced.With mineral fertilizer costs accounting for a significant percentage of production costs, this reduction consequently increases fertilizer efficiency i.e. lowers fertilizer inputs in livestock farming calculations.However, in these analyses, in addition to considering current prices, price forecasts should be made for the coming year, using data on the situation in livestock farming (number of animals) i.e. fodder requirements for the coming year and last year's hay stock.

Conclusion
The results suggest the potential to expand alfalfa production on pseudogleys in Serbia.
Using mineral fertillizers alone for alfalfa fertilization has no effect on the agrochemical properties of pseudogleys, but the addition of lime leads to a significant increase in alfalfa yield.
The combined application of 2.5 t ha -1 and 5 t ha -1 lime and 30 t ha -1 manure on the pseudogley increases the soil pH, humus content and available phosphorus and potassium levels, while decreasing the content of mobile aluminum, thus making the soil suitable for alfalfa production and high biomass yields (115.9 t ha -1 ) during 3-4 years of stand utilization.
When growing alfalfa on acid soils, the cost-effectiveness of mineral fertilizer and lime applications should be considered, along with the expectation that the initial high cost associated with stand establishment will be reduced in the coming years of stand utilization.

Table 1 .
Characteristics of pseudogley soil in Kraljevo and Dragčići

Table 4 .
Chemical composition of soil and plants inKraljevo (Dugalić et al.