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Production Papers

Effects of Application of Two Organomineral Fertilizers on Nutrient Leaching Losses and Wheat Crop

^a Departamento de Cristalografía, Mineralogía y Química Agrícola, EUITA, Universidad de Sevilla, Crta de Utrera, km. 1, E-41013, Sevilla, Spain
^b Departamento de Química Agrícola y Edafología, Universidad de Córdoba, Campus de Rabanales, Edificio C-3, Crta N-IV-a, km 396, E-14014 Córdoba, Spain

^* Corresponding author (mtmoral{at}us.es)

Received for publication April 1, 2004.

	ABSTRACT

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 
The topic of how to decrease environmentally adverse effects of agriculture without losing too much crop yield is an important issue. In this respect, nutrient leaching losses were studied from a soil (land fallowing is not practiced) treated with two types of organomineral fertilizers [organomineral fertilizer (OMF) and organic + inorganic fertilizer mixture (O+IF), respectively]. Inorganic N losses were greatest in the soil treated with the O+IF, followed by those treated with the OMF, the former of which resulted in more gradual losses than the latter. Losses of other elements supplied by the fertilizers, particularly P and K, were greatest for the O+IF, followed by OMF treatment. The high nutrient losses observed in the soil treated with the O+IF make it advisable to use an OMF in soils with an abundant water supply. The highest N/P ratios were produced by the OMF, which suggest a lower eutrophication risk in drainage waters from soils treated with this fertilizer. Wheat (Triticum aestivum L. cv. Cajeme) yield parameters obtained and the alveographic assays showed that the OMF has a great potential of being used, at least on the wheat variety tested and under the pedoclimatic conditions prevailing in the study area. In this respect, application of OMF gave a significant increase in grain gross protein content of 2.9%, an increase in number of grains per spike of 2.2%, a significant increase in number of spikes per square meter of 3.4%, an increase in 1000-grain weight of 3.9%, and a significant yield increase of 2.5% with respect to the O+IF treatment.

Abbreviations: OMF, organomineral fertilizer • O+IF, organic + inorganic fertilizer mixture

	INTRODUCTION

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 
THE DYNAMICS of plant nutrient uptake are quite complex and depend on crop growth stages. There is a time lag between fertilizer application and the absorption of applied nutrient by plant roots. During this period, the applied nutrients are vulnerable to environmental loss (Zhang and Solberg, 1996).

Nutrient leaching from incorrectly fertilized soils is known to have adverse environmental effects such as pollution and eventual eutrophication of running (river) and still (aquifers and reservoirs) waters, net phytoplankton productivity, and increased bottom water hypoxy (Justic et al., 1995; Rabalais et al., 1996). Also, the largest components of N leachates, NO₃^– and NO₂^–, can impact human (NRC, 1978; Mansouri and Lurie, 1993) and ruminant (Lewis, 1951) health. Finally, nutrient leaching can represent a significant economic loss to the farmer.

This environmental problem is made more acute by the fact that most ground water recharge takes place under agricultural areas and that more than 70% of the drinking water supply comes from ground water. Recent studies have shown that agriculture is directly responsible for more than 50% of the nitrogen that is leached into running waters because of mineral fertilizer application (Meissner et al., 1998; Hansen et al., 2000; Owens et al., 2000; Sogbedji et al., 2000). Correct usage of fertilizers is therefore essential to not only avoid wastage (and the associated productivity losses) but also to minimize the impact of leached nutrients (mainly nitrates and phosphates) on natural ecosystems (Macduff and White, 1984; Porta et al., 1994; Meissner et al., 1998; Granlund et al., 2000; Hansen et al., 2000; Owens et al., 2000; Sogbedji et al., 2000).

Several studies of alternative management strategies designed to maintain crop yield and return on investment while reducing nutrient losses have been performed in temperate regions using developed-world agricultural practices such as crop rotation (Martin et al., 1994; Moreno et al., 1996; Meissner et al., 1998; Zebarth et al., 1998; Granlund et al., 2000; Hansen et al., 2000; Stout et al., 2000; Loiseau et al., 2001). Although the practice of fallowing land was made obligatory by the reform of the Common Agricultural Policy in 1993, many farmers in southwest Spain cultivate a crop throughout the year, which increases the risks of eutrophication of rivers, aquifers, and reservoirs and soil erosion.

Torstensson et al. (1992), Schröder et al. (1993), Kemppainen (1995), Jackson and Smith (1997), and Hansen et al. (2000) suggested the use of organic fertilizers versus inorganic fertilizers to diminish the leaching losses of nutrients and thus the eutrophication of running and still waters. However, the organic matter added to soil, while greatly improving the physical properties of the soil, needs a certain time to mineralize and supply the nutrients needed by the crops. Moreover, a large quantity of product is needed to fulfill the nutritional requirements of the crops. This is the reason why some authors suggest the addition of mineral fertilizers at the same time to supply the nutrients that the plant requires in the early stages of development (Baron et al., 1995; Gonzalez et al., 1992; Tejada and Gonzalez, 2003a, 2003b). For this reason, OMF is one of the proposed means for reducing the losses of nutrients for Spanish agriculture. The Spanish authorities define OMF as a farming practice aiming to establish stable production systems with a high concern for nature and the environment. Obviously, the application of an organic product and the mineral fertilizer separately causes several problems, among which is their high cost of application. However, the combined application of both by means of a suitably balanced OMF would prevent that problem and allow the combined supply of mineral nutrients and organic matter.

Presently, the application of OMF to the soil is made in two ways: (i) as an organomineral formulation and (ii) as an organic + mineral fertilizer mixture. In this respect, Granlund et al. (2000) suggested the use of organic + mineral fertilizer mixture to decrease the leaching losses of nutrients. However, there are not many papers about nutrients leaching from organomineral formulation fertilizer.

The objective of this work was to study nutrient leaching losses from an intensively farmed soil (land fallowing is not practical) treated with two OMFs applied to the soil. In line with previous work of the authors (Baron et al., 1992; Benitez et al., 1995), the OMF used was applied in two different forms, namely as an organomineral formulation and as an organic + inorganic mixture. The second objective of this work was to test the action of this OMF on a wheat crop, by studying the wheat yield components.

	MATERIALS AND METHODS

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 
Soil and Fertilizers
The experiment was conducted in an Alfisol with Inceptisol intergradations (Soil Survey Staff, 1990). The general properties of this soil are shown in Table 1. In the experiment, we used two types of fertilizer, namely: (i) an organic fertilizer, O+IF, containing 2.5% humic extract, commercially available in suspended form (Humifluide, Agrifluide, Lora del Río, Sevilla, Spain) and (ii) an OMF with a 5:2.2:8.3 (N–P–K) formula and 2.5% of humic extract, marketed as a suspension by Agrifluide S.A. under the trade name Bioplus. The method used to manufacture organic and OMFs was described elsewhere (Baron et al., 1995).

Experimental Layout
The field experiment was conducted from October 1999 to June 2002 in the previously mentioned soil, located in Alcolea del Río, near to Córdoba city (Andalusia, Spain). Precipitation was variable throughout the study time (Table 3). The total annual rainfall was 308, 207, 330, and 337 mm for 1999, 2000, 2001, and 2002, respectively. The average mean air temperature was 18.8, 18.7, 18.9, and 18.8°C for 1999, 2000, 2001, and 2002, respectively. These values are typical of Mediterranean climate. Crops in the area are irrigated during the growing seasons. In this respect and for each experimental season, 200 mm of water was applied until wheat three-leaf stage, 250 mm of water was applied until wheat anthesis stage, and 150 mm of water was applied 30 d before wheat complete maturation stage. This amount of irrigation applied is common practice in the area for this crop. Table 4 shows the quality of irrigation water applied during the period of the investigation.

In September 1998, 10 lysimeters of methacrylate were installed in situ without disturbing the soil profile. The lysimeters were inserted into the soil, which was excavated around the lysimeters until arriving at the base, and a metallic plate was introduced to close the base of the lysimeter. Later, the lysimeters with soil were taken out of the terrain, and in their place, 30 cm was excavated to put another full gravel cylinder (80 cm) with an exit to gather the samples. Stairs were made to be able to access the bed part of the full gravel cylinder for sampling and analysis. Finally, the full soil lysimeters were placed on the full gravel cylinder, taking off the metallic plate (Fig. 1) .

View larger version (13K): [in this window] [in a new window]   Fig. 1. Design of the lysimeters.

Wheat (cv. Cajeme) was chosen as the test crop and seeded at a rate of 150 kg ha^–1, which is the common practice in the area. The sowing date was 17 Nov. 1999, 18 Nov. 2000, and 20 Nov. 2001, respectively.

Determinations in Drainage Water Discharge
Drainage water was sampled throughout the experimental period when the drain lines were flowing. The drainage water samples were frozen until analysis and subjected to the following analysis:

1. NH₄⁺–N by the colorimetric Kempers method (Kempers, 1974)
   
2. NO₂^––N and NO₃^––N by the colorimetric method of Griess and Illosvay as modified by Barnes and Tolkard (1951) and Bremner (1965)
   
3. Inorganic N, calculated as the combined amounts of NH₄⁺–N, NO₂^––N, and NO₃^––N
   
4. P by the method of Williams and Stewart as described by Guitian and Carballas (1976)
   
5. K by emission spectrometry
   
6. Ca, Mg, Fe, and Mn by atomic absorption spectrophotometry
   

Determinations in Grain, Wheat Yield Components, and Flour Quality
Protein content, weight of 1000 grains, number of spikes per square meter, number of grains per spike, and crop yield (kg ha^–1) were determined on samples collected in each plot on 14 June 2000, 13 June 2001, and 14 June 2002, respectively. The wheat was harvested by hand and done within the lysimeter area. Grain mineral composition was characterized by analyzing total N by the MAPA method (MAPA, 1986); P (Guitian and Carballas, 1976); Ca, Mg, K, and Na (GTNMA, 1976); and Fe, Cu, Mn, and Zn (Pinta, 1971). Flour quality parameters [tensile strength (P), inflation index (G), extensibility (L), and vigor (W)] were measured with a Chopin alveograph (MAPA, 1986).

Statistical Analysis
The results obtained were subjected to a multiple analysis of variance based on the LSD criterion, considering the fertilizer treatment and the three times sampled as the independent variables using the Statgraphic Plus for Windows 3.1 (Stat. Graphics Corp., 1994). The significance level considered throughout the study is p < 0.05.

	RESULTS AND DISCUSSION

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 
Macronutrient Forms
Figure 2 shows the losses in different inorganic forms of N from the fertilizer treatments. The results are obtained by averaging over the entire experimental period.

View larger version (27K): [in this window] [in a new window]   Fig. 2. Nitrogen losses (kg ha–1) in different inorganic forms from the soils. The results are obtained by average through the water collected in each phenological state for 3 yr. Error bars represent the standard error. OMF, organomineral fertilizer; O+IF, organic + inorganic fertilizer mixture.

The manufacturing process of the OMF (in a reactor at a higher temperature) may favor the more resistant fraction, which is initially integrated in the organic fraction, hence their stronger mineralization of this OMF (Tejada et al., 2002). For this reason, less losses of N forms occurred in treatment OMF. The use of stable OMF vs. O+IF is advisable.

On the other hand, and coinciding with Gustafson (1983), Bergström (1987), Ordoñez (1989), and Benitez et al. (1995), the highest losses were observed in the Time 1 (F ratio = 121 and p value = 0.008) percolations (40.9% of the total of the losses), with nitrate N as the most strongly leached fraction; this is also consistent with the results of Benitez et al. (1995). In addition, the highest losses in the different N fractions by effect of the Time 1 percolation were exhibited by the soil treated with the treatment O+IF. This is due mainly to the losses of N fractions coming from the mineral fertilizer and the N forms coming from the mineralization of the organic matter of the organic fertilizer.

Figure 3 shows the macronutrient leaching losses for the Time 1, Time 2, and Time 3 and the total leaching losses for each of the fertilizer treatments. For P, the highest losses, but not with significant differences, corresponded to the treatment O+IF, followed by treatment OMF (coinciding with the results of Baron et al., 1992). In this respect, there were 55.3% more losses of the treatment O+IF with respect to treatment OMF. The increased leaching of P from the soils treated with organic fertilizers may be a result of the mobility of organically bound phosphates (humophosphates) in the soil solution (Porta et al., 1994). The mineralization of the organic matter also contributes greater contents of this macronutrient (with respect to treatment OMF) and, therefore, the losses by leachates increases.

View larger version (27K): [in this window] [in a new window]   Fig. 3. Losses (kg ha–1) in different macronutrients forms from the soils. The results are obtained by average through the water collected in each phenological state for 3 yr. Error bars represent the standard error. OMF, organomineral fertilizer; O+IF, organic + inorganic fertilizer mixture.

As with P, the highest K losses, also not significant, occurred in the treatment O+IF and lowest in the treatment OMF, consistent with previous results of Baron et al. (1992). There were 29.6% more losses of the treatment O+IF with respect to treatment OMF. These greatest losses of K for the treatment O+IF are a consequence of the greater residual effect of this treatment (Tejada et al., 2002), which is that the mineralization of organic matter contributes greater contents of this macronutrient (with respect to treatment OMF), and therefore, the losses by leachates increases. The highest losses occurred within the first few percolations (Time 1), coinciding with Benitez et al. (1995).

Calcium and Mg losses, only significantly different for Mg (F ratio = 61.7 and p value = 0.016), were highest in the treatment O+IF and lowest in the treatment OMF. In this respect, for Ca, there were 24% more losses of the treatment O+IF with respect to treatment OMF. For Mg, there were 11.8% of highest losses of the treatment O+IF with respect to treatment OMF. As with K, the highest Ca and Mg losses were observed in the first few percolations (Time 1).

Quantifying P leaching losses is important because this element, together with N, causes water eutrophication. In this respect, the N/P ratio is more relevant to biological production than are the individual amounts of each element (Forsberg et al., 1978; Rhee, 1978; Pizzolon et al., 1999; Quiros et al., 2002). Although the N/P ratios that reportedly cause eutrophication are widely variable, values in the range from 5:1 to 60:1 are biologically productive; some authors, however, shorten the range to 5:1 to 15:1 for nitrate N and 6.4:1 to 25:1 for ammonia N. The N/P ratios derived from the fertilizer treatments studied in this work are given in Fig. 4 . Overall, the highest ratios (although without significant differences) were produced by the OMF, which suggests a lower eutrophication risk in drainage waters from soils treated with this fertilizer.

View larger version (24K): [in this window] [in a new window]   Fig. 4. Nitrogen/P ratios for the different treatments used. The results are obtained by average through the water collected in each phenological state for 3 yr. Error bars represent the standard error. OMF, organomineral fertilizer; O+IF, organic + inorganic fertilizer mixture.

View larger version (19K): [in this window] [in a new window]   Fig. 5. Iron and Mn contents (kg ha–1) in the leachates soils. The results are obtained by average through the water collected in the each one phenological state for 3 yr. Error bars represent the standard error. OMF, organomineral fertilizer; O+IF, organic + inorganic fertilizer mixture.

Like for the analyzed nutrients, these greater losses of Fe and Mn for the treatment O+IF are a consequence of the minor residual effect of this treatment (Tejada et al., 2002), which makes the mineralization of organic matter contribute greater contents of these micronutrients (with respect to treatment OMF), and therefore, the losses by leachates increases. This was the likely result of the chelating potential of humic substances in the OMF.

Wheat Yield Parameters
Table 5 shows the results obtained in the chemical analysis of the grains from the different plots, referred to as dry matter. With regards to the analyzed macronutrients, the most significant differences were found in N and K. For these macronutrients, the highest values were observed with treatment OMF. The N and K levels were higher than the values reported by Gonzalez et al. (1992) and Tejada and Gonzalez (2003a)(2003b) for the same wheat variety also grown in the Guadalquivir Valley under similar pedoclimatic conditions. The P, Ca, Mg, and Na levels did not show any significant differences with the fertilizer treatments applied, and these values were higher in the treatment OMF. With regards to the analyzed micronutrients, the most significant differences were found in Fe as for the applied fertilizer treatments, emphasizing the highest values for the treatment OMF.

Table 7 shows the results obtained in the normal and quiescent alveographic assays. The results reveal very extensible flours (L > 100), from balanced to tensile and quite strong (W > 300.10^–4 J). Significant differences between the analyzed parameters for the normal and quiescent assays and for two manufactured fertilizer treatments do not exist.

	CONCLUSIONS

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

	REFERENCES

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 

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