Acidity and low fertility of soils are limiting factors for the production of pastures and forages (Dos Santos et al. 2016). In Cuba, according to data from the Ministry of Agriculture, cited by Lok (2015), 26 and 46% are acid soils with low fertility, represented in a significant number of livestock enterprises in the country, and affected, in that order, by both factors. This problem is even more notable when analyzed per region.
Sabana de Manacas geographical region, located in the central area of Cuba, is very important for livestock production of that territory. It has soils of light texture, low natural fertility and high acidity (Hernández et al. 2015). Under these edaphic conditions, pastures become not very productive and deteriorate rapidly, which causes the appearance of invasive plants with little nutritional value for animal feeding (Pereira et al. 2018). Given these conditions, the application of technologies for their improvement constitutes a first order need to increase the productivity of pastures and extend their useful life.
Liming is the most used agricultural practice to correct soil acidity and, consequently, increase productivity of agricultural crops (Kryzevicius et al. 2019). However, pasture response to this labor has not been consistent, since, in some cases, lime applications have not been effective (Magalhães et al. 2017 and Pereira et al. 2018), and in others, its effect has been evident, even in species and cultivars tolerant to acidity and the presence of high levels of exchangeable aluminum in the soil (Biazatti et al. 2020).
The foregoing reinforces the argument that the response to liming may be related not only to the correction of acidity, but to its influence on nutrient availability in soil and with the species or cultivar of grass (Araújo et al. 2018 and Holland et al. 2018).
Based on these premises, the objective of this study was to evaluate the response of four species of Urochloa genus to liming, which are grown in an acidic soil with low fertility of Sabana de Manacas geographical region.
Materials and Methods
The experiment was carried out at Cascajal Pasture and Forage Station, located at 22° 39′ 44¨ North and 80° 29′ 36¨ West, in the Sabana de Manacas geographical region, Villa Clara province, Cuba, in a petroferric ferruginous nodular gley soil (Hernández et al. 2015), classified as stagnic fractipetric plintosol, according to the World Reference Base for Soil Resources (IUSS 2007). Table 1 shows its main chemical characteristics.
It is a highly acid soil, characterized by a strongly acid pH, high values of exchangeable acidity (H+ + Al3+) and a very low percentage of base saturation (V), as well as a low content of organic matter and very low amount of assimilable phosphorus and exchangeable cations (Paneque and Calaña 2001).
pH H2O |
OM (%) |
P (mg kg-1) |
Exchangeable bases | CEC | H++Al3+ | Al3+ | V(%) | |||
---|---|---|---|---|---|---|---|---|---|---|
Ca2+ | Mg2+ | Na+ | K+ | |||||||
(cmolc kg-1) | ||||||||||
4.8 | 2.52 | 5.5 | 3.32 | 1.12 | 0.05 | 0.1 | 4.59 | 4.33 | 0.06 | 51 |
(0.2) | (0.17) | (0.6) | (0.3) | (0.1) | (0.01) | (0.02) | (0.31) | (0.33) | (0.01) |
OM: organic matter, CEC: cation exchange capacity, H+ + Al3+: exchangeable acidity, V: base saturation
Values in parentheses indicate confidence intervals (α = 0.05)
Rainfall performance during the experimental period is shown in figure 1
Four doses of lime (0, 2, 4 and 6 t ha-1 of CaCO3) were evaluated in the pasture species Urochloa brizantha cv. Marandú, Urochloa decumbens cv. CIAT 606, Urochloa hybrid cv. 36087 (Mulato II) and Urochloa hybrid cv. CIAT BR02/1752 (Yacaré) in a random block design, with factorial arrangement and four replications. Plots constituted the experimental unit, with a total area of 21 m2 and a calculation area of 14 m2.
Soil was prepared by plowing (plow), harrowing, crossing (plowing) and harrowing, at approximate intervals of 25 d between each. Lime, with a content of 95% of CaCO3 and 90% of particles smaller than 5 mm, belonged to the Empresa Geominera del Centro, located in Remedios, Villa Clara. It was applied only once on the surface of the plots and it was included into the soil with the last harrowing labor.
Pasture sowing was carried out in May 2014, in rows separated by 50 cm and in drill sowing, with doses of 1 kg of pure germinated seed ha-1 and at 1.5 cm deep. The experiment lasted three years and it was conducted under dry conditions. An amount of 50 kg ha-1 of N of basal fertilization was applied, at 30 d after sowing, and after each cut during rainy season. At the beginning of each rainy season, 60 and 120 kg ha yr-1 of P2O5 and K2O were administered, respectively. Urea, triple superphosphate and potassium chloride were used as carriers.
Cuts were performed at a height of 10 cm from soil surface, at 120 d after sowing, and at intervals of 60 and 90 d during the rainy and dry season, respectively. In each cut, fresh mass of the aerial part of pastures that occupied the calculation area of plots was weighed and 200 g samples were taken. They were placed in an air circulation oven at 70 ºC for 72 h to determine dry mass percentage (DM), estimate DM yield, and concentrations of N, P, K and Ca in the biomass (Paneque et al. 2010).
From each plot, before the application of treatments (May, 2014), and after the last cut made in each dry period (April, 2015, 2016 and 2017), three soil subsamples were taken with a drill, at a depth of 0-20 cm, to form a compound sample. The pH was determined in H2O (potentiometry, soil-water ratio 1: 2.5) and the contents of organic matter (Walkley and Black), assimilable P (extraction with H2SO4 0.5 mol L-1 and colorimetric determination) and interchangeable bases (extraction with NH4Ac 1 mol L-1 pH 7, determination by titration with EDTA for Ca and Mg and flame photometry for Na and K). The cation exchange capacity (CEC) was calculated by adding the exchangeable bases and exchangeable acidity (H+ + Al3+) from the extraction with KCl 1 mol L-1 and titration, Al3+ by extraction with NaOH 0.0125 mol L-1 and titration, and the percentage of base saturation (V) by calculating CEC/CEC + (H++Al3+)/100. In all cases, the techniques established in the INCA soil and plant laboratory (Paneque et al. 2010) were used.
For statistical processing, data normality and homogeneity of variances were checked. The analysis of variance was used according to the experimental design and Duncan (Duncan 1955) multiple range test (P <0.05). For the chemical characterization of soil, as well as to evaluate the influence of lime doses on soil acidity indicators and its effect over time, the confidence interval (α = 0.05) was used as an estimator of mean variability and as a criterion for their comparison, respectively (Payton 2000). Regression analyzes were performed among variables related to soil acidity and grass yield, as well as between Ca concentrations in biomass and yields, and the equations with the best fit were selected. In all cases, the statistical program SPSS 25 (2017) was used.
Results
When comparing the results of soil analyzes of each treatment, carried out before lime application, and after the last cut of each dry period (figure 2), it was observed that liming significantly increased exchangeable Ca content, pH, cation exchange capacity and percentage of base saturation, and produced a significant decrease of exchangeable acidity of soil. This effect was proportional to the doses of applied lime, so that the highest results were observed with the addition of 6 t ha-1.
The greatest influence of liming on these variables was observed during the first two years. In the third, although the doses of 4 and 6 t ha-1 of lime maintained their effect with respect to the lowest dose and the control without lime, it was significantly lower than in previous years.
There was no interaction among lime doses and pasture species for dry mass yield. However, the levels of both factors showed significant differences between them (table 2). The highest yields, in rainy and dry season, were reached with the doses of 4 and 6 t ha-1 of lime during the first two years of its application. In the third, the liming effect disappeared, coinciding with the decrease in the influence of the amendment of exchangeable Ca content and the reduction of soil acidity. Among pasture species, the highest dry mass yields were reached by Yacaré.
CaCO3 (t ha-1) |
First year | Second year | Third year | ||||||
---|---|---|---|---|---|---|---|---|---|
Rainy season | Dry season | Total | Rainy season | Dry season | Total | Rainy season | Dry season | Total | |
0 | 6.20 c | 2.07 c | 8.26 c | 5.42 c | 2.06 c | 7.22 c | 5.94 | 1.98 | 7.92 |
2 | 7.42 b | 2.38 b | 9.85 b | 6.41 b | 2.14 b | 8.55 b | 6.08 | 2.03 | 8.10 |
4 | 8.75a | 2.92a | 11.66a | 7.67a | 2.56a | 10.22a | 6.11 | 2.04 | 8.14 |
6 | 8.57a | 2.86a | 11.42a | 7.78a | 2.59a | 10.37a | 5.90 | 1.97 | 7.87 |
SE | 0.19** | 0.07** | 0.24** | 0.18** | 0.06** | 0.22** | 0.15 | 0.06 | 0.16 |
Species | |||||||||
|
7.22b | 2.41b | 9.62b | 6.41b | 2.14b | 8.55b | 5.59b | 1.86b | 7.45b |
|
7.33b | 2.44b | 9.77b | 6.47b | 2.16b | 8.62b | 5.20b | 1.73b | 6.93b |
|
7.39b | 2.46a | 9.85a | 6.59b | 2.20a | 8.79b | 5.65b | 1.88b | 7.53b |
|
8.94a | 2.98a | 11.92a | 7.78a | 2.59a | 10.37a | 7.42a | 2.47a | 9.89a |
SE± | 0.22** | 0.08** | 0.27** | 0.20** | 0.07** | 0.25** | 0.20** | 0.06** | 0.18** |
Means with different letters in the same column differ significantly at P < 0.05 (Duncan 1955)
By relating annual yields of pastures with the performance of the variables that characterize acidity, according to the results of soil analyzes carried out each year, quadratic trend regression equations were found with high fit levels (values of R2 higher than 0.90), as shown in table 3. That is, the increase of yields was associated with pH increments, exchangeable Ca content and base saturation percentage, as well as a decrease of soil exchangeable acidity.
Equations | SE± | R2 |
---|---|---|
Y= - 0.71 (±0.525)x1 2 + 9.77 (±0.15)x1 - 22.75 (±0.87) | 0.55 | 0.92** |
Y= 8.94 (±0.46)x2 2 - 64 (±0.13)x2 - 20.44 (±0.77) | 0.47 | 0.95** |
Y = - 0.41 (±0.11)x3 2 + 0.51(±0.24)x3 + 10.99 (0.26) | 0.42 | 0.95** |
Y= - 0.003 (±0.0009)x4 2 + 4.95 (±0.11)x4 - 12.10 (±0.66) | 0.48 | 0.93** |
Y: dry mass yield (t ha-1),
x1: pH H2O,
x2: exchangeable Ca (cmolc kg-1),
x3: H + + Al3+ (cmolc kg-1),
x4: V (% base saturation)
Values in parentheses indicate standard error of the terms of the equations, ** P <0.01
Liming and pasture species had no effect on N and P concentrations in the biomass. However, Ca concentrations increased significantly with lime additions, reaching the highest values with doses of 4 and 6 t ha-1 (table 4).
CaCO3 (t ha-1) |
N | P | K | Ca | ||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
1 | 2 | 3 | 1 | 2 | 3 | 1 | 2 | 3 | 1 | 2 | 3 | |
0 | 16.4 | 15.4 | 16.3 | 2.2 | 1.8 | 2.2 | 14.9a | 14.9a | 15.3 | 3.0c | 3.2c | 3.1 |
2 | 15.9 | 16.1 | 15.6 | 2.1 | 1.9 | 2.2 | 15.6a | 15.2a | 14.7 | 4.1b | 4.3b | 3.4 |
4 | 15.7 | 15.7 | 16.0 | 2.2 | 2.3 | 2.3 | 15.7a | 14.7a | 15.0 | 5.2a | 5.6a | 3.0 |
6 | 16.4 | 15.3 | 15.1 | 2.2 | 2.0 | 2.2 | 13.1b | 13.0b | 15.1 | 5.4a | 5.7a | 3.5 |
SE± | 0.3 | 0.4 | 0.3 | 0.1 | 0.1 | 0.1 | 0.3* | 0.4* | 0.3 | 0.1* | 0.1* | 0.2* |
| ||||||||||||
|
15.7 | 16.0 | 15.2 | 2.3 | 1.9 | 2.3 | 14.9 | 14.9 | 15.3 | 4.5 | 4.6 | 3.5 |
|
16.5 | 15.2 | 16.1 | 2.2 | 2.0 | 2.4 | 15.6 | 15.2 | 14.7 | 4.3 | 4.7 | 3.4 |
|
16.6 | 15.4 | 15.9 | 2.2 | 1.9 | 2.3 | 15.7 | 14.7 | 15.0 | 4.5 | 4.5 | 3.2 |
|
15.9 | 16.1 | 15.7 | 2.1 | 1.8 | 2.2 | 13.1 | 13.0 | 15.1 | 4.4 | 4.8 | 3.2 |
SE± | 0.2 | 0.3 | 0.4 | 0.2 | 0.2 | 0.1 | 0.4 | 0.4 | 0.3 | 0.1 | 0.2 | 0.1 |
1: first year,
2: second year,
3: third year
Means with different letters in the same column differ significantly at P < 0.05 (Duncan 1955)
With the addition of the highest dose of lime, there was a decrease of K concentrations in biomass. As in yield, the influence of the amendment in the concentrations of both nutrients was maintained during the two years after its application.
By relating the annual concentrations of Ca in the biomass with dry mass yield (t ha-1 year-1), a quadratic trend regression equation and a high value of R2 were obtained. This showed that the increase of yields was also associated with the increase of contents of this element in forage (table 5).
Discussion
The influence of liming on acidity reduction can be attributed to the displacement of exchangeable H and Al by Ca, provided by the liming material and, consequently, to the increase of the concentration of OH ions in the soil solution as a result of these reactions, which agrees with reports of Opala et al. (2018) and Dereje et al. (2019).
Regarding the permanence of liming effect on the reduction of soil acidity, Da Costa et al. (2016) and Abdi et al. (2017) observed that it lasted up to 48 and 60 months, respectively, a time longer than that observed in this research. However, it has been shown that lime residuality depends on the nature of the liming material, doses and forms of application, as well as the properties of soil and crop (Li et al. 2018).
The relationships found among the modifications of variables that characterize soil acidity and yield increase were interesting, because, although the effect of acidity decrease in biomass production has been evident in other pasture species (Gatiboni et al. 2017), it is known that the species of Brachiaria (syn. Urochloa) genus tolerate acidic conditions, and even, high levels of exchangeable aluminum (Salgado et al. 2017 and Worthington et al. 2019). This was not observed in the soil where this experiment was carried out, in which exchangeable acidity was a result, mainly, of the presence of H, since the saturation level of Al, understood as the percentage value of this element in relation to the cation exchange capacity [CEC + (H + + Al3+)], was only 0.7%.
Nevertheless, some authors, in studies with Urochloa species, found a response to lime applications due to the reduction of acidity and exchangeable Al contents (Biazatti et al. 2020). Other studies observed that the increase of yields was related to the improvement of the nutritional status of plants, from the increase in the content of nutrients in the soil and in the biomass (mainly Ca and P) or with a better use of fertilizers (Costa et al. 2012 and Teixeira et al. 2018).
Although lime applications of the current study did not influence on N and P contents in the biomass, probably due to the use of a basal fertilization, which guaranteed the nitrogen (at least during rainy season) and phosphoric nutrition of plants under the effects of liming, the high relationship between Ca concentrations in biomass and yields indicate that the contribution of this element helped to improve calcium nutrition and, in fact, to increase pasture productivity. This is logical, if the low initial content of exchangeable Ca in the soil is considered.
Dos Santos et al. (2016), in an extensive bibliographic review on the importance of liming for the production of forage plants, pointed out that, in soils with very low exchangeable Ca contents, lime promotes increases in the concentrations of this element in biomass and, consequently, in pasture yields.
The decrease of K concentrations in biomass, registered during the first two years with the application of the highest lime dose, seems to be the consequence of the expression of a possible antagonism, due to the contribution of a quantity of Ca that could have limited absorption of K by plants. Da Costa et al. (2016) also observed this effect with the addition of high doses of liming materials in soybean-oat-sorghum crop rotations.
Regarding the performance of yields, during the first two years, the response to liming was evident, even in dry season, despite the fact that nitrogen fertilizer was not applied during this time because the experiment was conducted under non-irrigation conditions. However, it was demonstrated that lime additions stimulate root growth, as a consequence of reducing soil acidity. This facilitates the absorption of nutrients and water and, in fact, favors the growth of plant aerial biomass (Zang et al. 2020).
In the third year, yields were reduced by 35 and 22% compared to the first and second years, respectively. This can not only be attributed to the fact that no response to lime was found during this period, but to the performance of rainfall, which decreased by 27% compared to previous years.
Another interesting aspect was the best performance of Yacaré grass in relation to the other species evaluated in this study. Although this cultivar has shown better yields and persistence levels compared to other Urochloa species (Pentón et al. 2018) in some regions of Cuba, the fact that it has reached higher productivity in acidic and low fertility soils indicates that, besides liming, the inclusion of Yacaré grass may also be an option to increase biomass production under these edaphic conditions.
Conclusions
Liming improves calcium nutrition and increases the productivity of Brachiaria genus pastures, cultivated in an acidic soil with low fertility in Sabana de Manacas region. Its greatest effects on soil and yields are maintained during the first two years. The application of 4 ha-1 of lime is recommended.