Combined N, P, K fertilization and liming maximises crop productivity of acid loams in Lithuania

Abstract

Crop response to fertilization and liming was investigated in field and pot trials on sandy loam Dystric Albeluvisols (pH 4.2–4.3). Treatments in the field trial were: 1, no fertilizer; 2, PK; 3, NK; 4, NP; 5, NPK; 6, lime; 7, lime+PK; 8, lime+NK; 9, lime+NP; 10, lime+NPK. In the pot trial, they were: 1, no fertilizer; 2, N; 3, P; 4, K; 5, NP; 6, NK; 7, PK; and 8, NPK applied to unlimed and limed soils. All treatments were in four replicates. Crops sensitive to soil acidity (winter wheat, fodder beet, spring barley and clover-timothy ley) and the less acid-sensitive winter rye, potatoes, oats and lupins and oats mixture were sown in the field trial. In the pot trial, the acid-sensitive spring barley and red clover, and the less acid-sensitive oats and lupin-oats served as the test crops. Combined application of fertilizers (NPK) increased yields of crops sensitive to soil acidity in plots receiving lime by 23%, and those of crops less sensitive to soil acidity by 18% in comparison to crops grown on unlimed soils. The results of pot experiments corroborated the field results. When N was applied alone, crop yields were always higher than those recorded for P or K treatments on both the unlimed and limed treatments. N application proved to be a prerequisite for high crop yields in the soils investigated. Thus, the efficiency of P and K fertilizers increased in the order NK<NP<NPK, with the effects being accentuated more in the limed than in the unlimed treatments. The results demonstrated the importance of multi-nutrient (NPK) fertilization in combination with liming for enhancement of high crop productivity in the unlimed soil investigated. N applied alone in combination with liming produced relatively good yields; hence, where resources are limited for the purchase of P and K fertilizers, applying N and lime can be a viable option in the short term.

Keywords:

• acid sensitive crops
• less acid sensitive crops
• liming
• mineral fertilization
• pH tolerance
• pot and field trials

Introduction

The main reason for applying Ca and Mg as lime to acid soils is not to supply Ca or Mg to the crops, but to adjust the soil pH to a level that ensures availability of soil nutrients. Optimum pH (in water) values differ according to the crop. For example, in the United Kingdom optimum pH is 5.0 for potatoes and oats, and 6.5–7.0 for barley and spring beans (Johnston & Whinham, 1980). The critical soil pH values below which crop growth is restricted on mineral soils are: 6.0 for beans, 5.9 for red clover, barley and sugar beet, 5.5 for wheat, 4.7 for meadow fescue, 4.9 for potatoes, 5.3 for oats and timothy and 5.4 for swedes (Wild, 1988). Optimum soil pH values for the availability of the major nutrients are 6–8 (N), 6.5–7.5 (P), >6 (K and S), and 7–8.5 (Ca and Mg) (Archer, 1985; Foth, 1990).

Soil degradation by acidification, resulting from acid deposition, microbial processes and root exudation is a natural process. However, in the last 150 years, the natural acidifying processes have been enhanced by man-made practices, such as the use of ammonium-based fertilizers and repeated cropping of legume crops. While sulphur compounds were the principal manufactured component of acid rain 25 years ago, N compounds now predominate (Goulding & Annis, 1998). Among analysed factors, SO₂ emission is the largest source of acidity in Poland, where S accounted for 52–55% of the total acidification load, with N fertilizers contributing 30–45% (Filipek, 1997).

According to data from agrochemical soil investigations collected in Lithuania between 1963 and 1967, naturally occurring acid soils (pH≤5.5) accounted for 40.7% of cultivated land, of which 11.9% were very acidic (pH≤4.5). About 15.8% were strongly acidic (pH 4.6–5.0) and 13% were moderately acidic (pH 5.1–5.5). Moreover, about two-thirds of the acid soils were in western Lithuania. Through intensive liming, the area of acid soils has been reduced. According to data collected between 1985 and 1993, there were only 18.8% of acidic soils in the Republic, of which 1.5%, 7% and 10.2% were strongly, moderately and weakly acidic, respectively (Mažvila et al., 1998).

Liming of acid soils is a common management practice. Applying full rates of CaCO₃ to neutralise hydrolytic acidity is essential for the rehabilitation of the strongly acid dystric albeluvisols, the soils investigated in this study. Liming not only increases soil pH and base saturation, but it also immobilises Al ions, which are toxic to crops, thereby creating conditions more favourable for the growth of crops. Subsequent to liming strongly acid soils the average additional yield harvested in Lithuania over 20 years was 3180 feed units ha⁻¹ (Plesevičienė & Jankauskas, 2000).

The determinant role of N in plant nutrition as well its impact on crop response to K and P fertilizers has been demonstrated in different soil conditions (Jankauskas, 2000; Petraitienė, 1997; Vaišvila, 1996). However, there are some unresolved issues, such as the correct fertilizer balance for crops with different susceptibility to soil acidity and Al toxicity. Therefore the objective of this study was to determine the impact of N, P and K fertilizers and fertilizer-lime interactions on crop productivity.

Materials and methods

Geographic location and climatic conditions

Studies were carried out at the Vėžaiciai Branch of the Lithuanian Institute of Agriculture located 20 km from the Batticsoo (55°71′N, 21°50′E), with an average annual solar radiatior 33 kkat, cm⁻², temperature of 6°C tanging between −4.8 and 17.2°C and a precipation of 765 mm.

Field trials

The efficiency of mineral nutrients was studied in field and pot experiments on the sandy loam Dystric Albeluvisol (Driessen, 2001) at Vėžaiciai (Jankauskas, 1998). The results are summarised here and compared with pot trials. The treatments in the field experiments were: 1, no fertilizer; 2, PK; 3, NK; 4, NP; 5, NPK; 6, lime; 7, lime+PK; 8, lime+NK; 9, lime+NP; and 10, lime+NPK, each having 4 replicates. Soil samples were taken within the 0–20 cm layer prior to the start of the field experiment. Some of soil chemical properties were as follows: pH 4.2–4.3, hydrolytic acidity 4.5–5.5 cmol (+) kg⁻¹, extractable P and K contents 4.4–6.5 and 49.8–71.4 mg kg⁻¹, respectively. Base saturation was 36.1–40.9%. Two field trials were carried out. Crops sensitive to soil acidity were grown in field Trial 1 in which the crop rotation was: 1, winter wheat (Triticum aestivum L.); 2, fodder beet (Beta vulgaris L.); 3, spring barley (Hordeum vulgare L.) as a nurse crop and 4, a mixture of clover-timothy (Trifolium pratense L.-Phleum pratense L.). In Trial 2, crops less sensitive to soil acidity were grown and the crop rotation was: 1, winter rye (Secale cereale L.); 2, potatoes (Solanum tuberosum L.); 3, oats (Avena sativa L.) and 4, a mixture of lupin-oats (Lupinus luteus L.-Avena sativa L.). The duration of the field experiments was eight years (two 4-course crop rotations). Liming was carried out once at the beginning of the experiments by applying the full rates of CaCO₃ relative to hydrolytic acidity (6.75–8.25 t ha⁻¹). Cattle manure (30 Mg ha⁻¹) and N (90 kg ha⁻¹), P (39 kg ha⁻¹) and K (100 kg ha⁻¹) mineral fertilizers were applied to the fodder beet and potatoes. The mineral fertilizers were applied as ammonium nitrate, superphosphate and muriate of potash (KCl) for N, P and K, respectively. Mineral fertilizers only were applied to cereals and crop mixtures at rates of N (45 kg ha⁻¹)_, P (26 kg ha⁻¹), K (75 kg ha⁻¹) and N (30 kg ha⁻¹)_, P (26 kg ha⁻¹)_, K (100 kg ha⁻¹), respectively.

Pot trials

The pot trials were carried out in more detail. They consisted of: 1, no fertilizer (hereafter referred to as nil); 2, N; 3, P; 4, K; 5, NP; 6, NK; 7, PK; and 8, NPK in both unlimed and limed situations. The total number of treatments was 16, both for crops sensitive to soil acidity and less sensitive to acidity. There were 4 replicates of each treatment. The bulk soil samples used in the pot trial were taken from the plough layer (0–20 cm) of the sandy loam dystric albeluvisol. Some of its chemical properties were as follows: pH 4.2, hydrolytic acidity 4.7 cmol(+)kg⁻¹, amount of extractable P and K 5.2 and 81.3 mg kg⁻¹, respectively. Samples of 6.5 kg dry soil were homogenised with 31.9 g CaCO₃ kg⁻¹, 0.033 g P kg⁻¹, and 0.125 g K kg⁻¹. A solution of ammonium nitrate containing 0.15 g N kg⁻¹ was applied after thinning the plants (Zurbickij, 1968).

The crops were grown for three years without changing soils, but applying fertilizers to replace the removed nutrients in the following sequence: spring barley, red clover and spring barley as the crops sensitive to soil acidity, and oats, lupins-oats as the crops less sensitive to soil acidity. The following number of plants remained in the pots after thinning: 12 (spring barley and oats), 15 (red clover) and 8 (lupins). The wide diversity of crops in terms of those sensitive (spring barley, red clover) and less sensitive (oats, lupins) to soil acidity represented crops with differing mineral nutrition requirements.

Soil analysis

For historical reasons, Russian techniques of soil analysis techniques were mainly used. Soil pH was determined in 1M KCl soil extracts using a calibrated digital pH meter. Hydrolytic acidity was determined in 1M CH₃COONa and soil extract (ratio sample:extract 1:25 for mineral soil) by titrating with 1M NaOH (Askinazi, 1975). Exchangeable bases were determined by the Kappen-Hilkovic method, which involves hot titration of 0.1M HCl and soil sample filtrate (ratio sample:extract 1:5) with 0.1 M NaOH (Askinazi, 1975). Ca⁺⁺, Mg⁺⁺, K⁺, Na⁺ and NH₄ ⁺ concentrations were determined on filtrates. The base saturation was calculated using the formula:

Where V is base saturation in percent, S is exchangeable bases in cmol(+)kg⁻¹, H is hydrolytic acidity in cmol(+)kg⁻¹.

Available P and K were extracted with ammonium acetate-lactate (A-L solution pH 3.7; ratio 1:20) (Egnćr et al., 1960). The extracted P was determined on a spectrophotometer and K on a flame photometer (Egnćr et al., 1960; Vazenin, 1975; Ginzburg, 1975).

Results and discussion

The results obtained in the field trials were reported elsewhere (Jankauskas, 1998) and only a summary is presented in this study. It was noted there that crops sensitive to soil acidity (winter wheat, fodder beet, spring barley, clover-timothy mixture) were more productive on both the limed and fertilized soils. Similarly, crops less sensitive to acidity (winter rye, potatoes, oats and lupin-oats mixed) also positively responded to fertilization on both the unlimed and limed soils, but the results were less marked. Combined application of fertilizers (NPK) increased yields of crops sensitive to soil acidity in plots receiving lime by 23%, and of crops less sensitive to soil acidity by 18% compared with crops grown on unlimed soils. The dual-nutrient fertilizers (N+P, P+K and N+K) gave smaller yield increases than the compound fertilizer. The efficiency of dual-nutrient fertilizers decreased in the following descending order: NP<, NK<PK. P efficiency was higher (but not significantly), and K was significantly higher on the limed soils for both crop groups than on the unlimed soils. Response to N by crops sensitive to acidity was significantly higher on the unlimed than limed treatment. No significant differences were recorded for crops less sensitive to acidity (Fig. 1). The efficiency of P was higher than that of K. Liming significantly increased K efficiency for both crop groups; it did not affect P efficiency, and decreased that of N. More detailed presentation of the results obtained in the field trials was published by Jankauskas (1998).

Fig. 1 Efficiency of N, P and K on unlimed (A) and limed (L) soil. S – crops sensitive to soil acidity, LS – crops less sensitive to soil acidity; F.u. – feed unit; *The basic productivity for calculation of extra yield of crops sensitive to acidity was 2700 f.u. ha⁻¹ for the acid soil and 3200 f.u. ha⁻¹ for the limed soil, while for crops less sensitive to acidity it was 3450 and 3830 f.u. ha⁻¹, respectively.

It is not clear (Fig. 1) why crops sensitive to soil acidity produced higher additional yields than crops less sensitive to soil acidity in both the unlimed and limed soils. A possible explanation for these conflicting responses could be ascribed to inclusion of leguminous crops such as red clover in the crop rotation of crops sensitive to soil acidity. Crops following the leguminous crops could have benefited from N symbiotically fixed by the legumes. Less acid-tolerant crops performed poorly in the unlimed treatments, especially in the K treatment against the regime of unlimed NK. The additional yields in the K treatment were about 60 f.u. ha⁻¹, compared with the majority of treatments which produced 400–1000 f.u. ha⁻¹. The low additional yield could possibly be due to an excess of available K in the soils, which behaved antagonistically in relation to plant Ca- and Mg-nutrition.

Table 1 shows results of pot trials with the crops sensitive to soil acidity. Yields of spring barley preceding red clover ranged from about 2.5 to 12 g pot⁻¹ in the unlimed soils and 6–26 g pot⁻¹ in the limed ones. Yields were significantly increased by 2.8–3 times in the NP and NPK treatments compared with nil-treatment. K applied alone was inferior to N applied alone. The best treatment was NPK in both unlimed and limed soils and means were statistically different regardless of crop type. The highest barley yields of about 55 and 63 g pot⁻¹ were recorded in the NPK treatment. The spring barley preceding red clover was inferior in terms of yield output to spring barley following red clover. A similar pattern was recorded for crops less sensitive to soil acidity, e.g. oats and lupins (Table 2), except that lupin dry matter yields on the nil-treatment exceeded those obtained on N and NK treatments. The yield of oats grown preceding lupins increased significantly under all treatments including N nutrition (N, NP, NK and NPK) compared with the nil-treatment, on both acid and limed soils. However, the highest yields were obtained in the NPK treatments. Where oats preceded lupins, yields were increased with liming, but where oats followed lupins, yield increases were less pronounced. Indeed, the efficiency of liming became negative on K, NP and NPK treatments. Of fertilizers applied alone, only P produced lupin yields in line with those of NPK, the treatment which produced the highest yields on both unlimed and limed soils. This implies that lupins did not benefit from liming and application of N and K fertilizers.

Table 1. Response (mean values) to fertilization and liming of crops sensitive to soil acidity grown in pot experiment

	Yield in g pot^−1 of dry matter
	Spring barley		Red clover		Spring barley
Treatments	Unlimed	Limed	Unlimed	Limed	Unlimed	Limed
Nil	4.1	6.1	3.6	6.7	2.4	5.6
N	2.5	13.8	5.9	8.9	8.0	9.6
P	5.2	6.7	8.9	15.5	7.3	11.7
K	3.6	5.8	2.0	6.3	2.7	3.1
NP	11.3	15.6	11.8	21.0	31.5	30.1
NK	2.6	11.5	7.7	18.8	13.1	8.9
PK	5.7	7.4	6.6	24.1	5.0	11.5
NPK	12.1	25.7	25.6	31.8	54.8	62.5
*LSD05	3.1	1.4	3.6	2.6	5.8	2.3
**LSD05	2.2		2.9		4.1
* Comparisons are made in downward columns. **Columns make comparisons for each pair of means in the unlimed and limed treatments.

Table 2. Response (mean values) of crops less sensitive to soil acidity to fertilization in pot trials

	Yield in g pot^−1 of dry matter
	Oats		Lupins after oats		Oats after lupins
Treatments	Unlimed	Limed	Unlimed	Limed	Unlimed	Limed
Nil	7.1	8.7	52.7	44.6	3.7	6.6
N	12.4	21.4	22.2	17.8	5.9	7.3
P	7.5	8.6	62.5	61.3	6.2	8.0
K	5.9	8.5	43.0	48.3	2.5	2.0
NP	28.0	38.4	53.6	48.9	30.7	24.4
NK	11.2	20.5	10.4	24.6	6.5	9.0
PK	7.8	8.9	57.5	50.0	6.7	9.7
NPK	38.8	41.7	63.3	62.8	62.7	56.5
*LSD05	3.8	6.6	6.2	5.1	3.6	4.6
**LSD05	5.0		5.2		3.9
* Comparisons are made downward for each column. **Comparisons are made for each pair of unlimed and limed treatments.

Fertilizer P significantly increased the yield of red clover under all fertilization regimes on the acid and limed soils (Fig. 2). Liming also increased the efficiency of P under all regimes. However, the highest influence of liming was under the K nutrition regime (PK treatment). Liming increased the efficiency of P nutrition under this regime by 3.9 times. K increased the additional yield of red clover significantly under NP, P and N regimes and the greatest increase was from the dual-nutrient NP fertilization regime on both the acid and limed soils (Fig. 2). Even N nutrition alone significantly increased yields of red clover on the triple-nutrient fertilization regimes of both acid and limed soil. The greatest increase in clover yield (19 g pot⁻¹) was from the PK regime on acid soil (Fig. 2).

Fig. 2 Influence of N, P and K on the additional yield* of red clover on unlimed and limed soils. *DM: dry matter on (A) acid soil and (L) limed soil.

P increased the additional yield of lupins under the all investigated fertilizer regimes. The highest (52.9 g pot⁻¹) additional yield was under the NK fertilizer regime on acid soil (Fig. 3). K increased the additional yield of lupins significantly on the NP fertilizer regime on both acid and limed soil, and on the N regime on limed soil. The influence of K was negative under N alone, and unfertilized acid soil and on P background of limed soil. The positive reaction of lupins to N fertilizer occurred only in the PK fertilizer regime. The significantly negative influence of N was on the P, K and unfertilized on both acid and limed soils (Fig. 3).

Fig. 3 Influence of N, P and K on the additional yield* of lupins on unlimed and limed soils. *DM: dry matter on (A) acid soil and (L) limed soil.

Data on the influence of N on additional yield of spring barley and oats are given in Fig. 4. The data are based on the averages of two yields: one obtained before and the other obtained after the clover crop. Additional yields gradually increased from the nil treatment<K<P<PK both on unlimed and limed soils. The greatest additional yield of 34.6 g pot⁻¹ was determined in the PK regime. This figure was 6 times higher than the one determined in the nil-, 6.7 times higher than in the K- and 2 times higher than in the P-regimes. Furthermore, additional barley yields as influenced by P and K fertilization were computed and the results are presented in Figs. 5 and 6. Similar patterns were observed to those noted in Fig. 4. These results reflect those presented earlier in Tables 1 and 2.

Fig. 4 Influence of N on the additional yield of spring barley and oats. Average of 2 trials (before and after clover or lupins). *DM: dry matter on (A) acid soil and (L) limed soil.

Fig. 5 Influence of P on the additional yield of spring barley and oats. Average of 2 trials (before and after lupins or clover). *DM: dry matter on (A) acid soil and (L) limed soil.

Fig. 6 Influence of K on the additional yield of spring barley and oats. Average of 2 trials (before and after clover or lupins). *DM dry matter on (A) acid soil and (L) limed soil.

Conclusions

Based on the results of the investigations, those crops sensitive to acidity could be grown on limed soils using optimal rates of mineral fertilizers. Crops less sensitive to acidity could be grown on acid soil using reduced rates of mineral fertilizers. The latter suggestion is especially important for the Baltic States, where liming of acid soils and use of fertilizers is limited by economic necessity.

The results of pot investigations confirmed the importance of compound fertilizers (NPK). The highest efficiency of the three fertilization was obtained when the three nutrients, i.e. N, P and K were applied together. (Figs. 5 and 6). The inclusion of N nutrition into the full nutrition composition was important not only for cereal grains, but also for (Fig. 4), even for the leguminous red clover (Fig. 2) and lupins (Fig. 3), because the biological activity of strongly acid soil was low especially in the first year of the investigations. Essentially, liming of acid soil improved the growing conditions of crops sensitive to soil acidity (Table 1); however, the influence of complete mineral nutrition was more important.

Lupins could be grown with application of P, omitting liming and applying N and K fertilizers.

Additional information

Notes on contributors

Benediktas Jankauskas *

Jankauskas, B. and Otabbong, E. (Kaltinenai Research Station of Lithuanian Institute of Agriculture, Varniu 17, LT-5926 Kaltinėnai, Šilalė District, Lithuania and Department of Soil Sciences, Swedish University of Agricultural Sciences, P.O. Box 7014, SE-750 07 Uppsala, Sweden). Combined N, P, K fertilization and liming maximises crop productivity of acid loams in Lithuania. Accepted December 11, 2003.

Notes

Jankauskas, B. and Otabbong, E. (Kaltinenai Research Station of Lithuanian Institute of Agriculture, Varniu 17, LT-5926 Kaltinėnai, Šilalė District, Lithuania and Department of Soil Sciences, Swedish University of Agricultural Sciences, P.O. Box 7014, SE-750 07 Uppsala, Sweden). Combined N, P, K fertilization and liming maximises crop productivity of acid loams in Lithuania. Accepted December 11, 2003.