Phosphate fertilizers when applied to the soil, besides being harvested by the crops, promote a residual effect that can be offered to subsequent crops. The objective of this research was to evaluate the residual effect of phosphate fertilization applied to maize cultivation on the successor crop, cowpea, in the Cerrado region in Maranhao. The research was carried out in the experimental area of Federal University of Maranhao (UFMA), located in the city of Chapadinha, MA (3 °44'30"S, 43°21'37''W). The experimental design was in randomized blocks, with six treatments and four replications. The treatments were composed of the following residual P doses: 0, 60, 70, 80, 90, 100 kg·ha-1 of P2O5. The cultivation of cowpea (cultivar BRS guariba) was sown at a spacing of 1.0 × 0.20 m. The cowpea proved to be efficient in the use of residual phosphate fertilization, since it promoted grain yield close to the national average. The cultivation of cowpea in previously cultivated areas is feasible, in order to take advantage of the residual phosphate fertilization in the Cerrado of East of Maranhao. The phosphorus dose applied in the predecessor crop corresponding to 80 kg·ha-1 of P2O5 promoted higher grain yield (393.44 Mg·ha-1) and a greater profit margin (US $326.26). Thus, it is feasible to grow cowpea in previously cultivated areas, in order to take advantage of residual phosphate fertilization.
The production of cowpea (Vigna unguiculata L. Walp) in Brazil is an activity carried out mainly by small producers. However, it assumes an important socioeconomic role, especially for the North and Northeast Regions, as it is one of the main sources of protein and low-cost carbohydrates available in the rural zone [
The residual effect of phosphate fertilizers depends on factors such as the doses and sources of phosphorus used, method of application of phosphate fertilizers, management, temperature, soil type, application time, soil moisture and type of crop (Coutinho et al., 2014). Therefore, succession of cowpea after maize cultivation is an interesting strategy for the use of phosphate fertilizer residues [
There are several factors that influence the efficiency of phosphate fertilization mainly related to soil, plant, management, and the sources of phosphorus used. The main factors related to the agronomic efficiency of the sources are the phosphorus content soluble in the different fractions or extractive solutions (water, neutral ammonium citrate and citric acid) [
On the other hand, when phosphatic fertilizers are applied to the soil, besides the immediate use of the crops, they may also have a residual effect that can be offered to subsequent crops [
The application of phosphate fertilizers in the cultivation in succession of maize-cowpea is a strategy that may favor small producers, who often lack the resources to acquire certain inputs, such as phosphorus, which are essential for the formation of pods and fodder of grains, reflecting crop productivity [
In this sense, the residual phosphorus effect in the soil has been evaluated by several authors in common bean as a function of soil pH [
The research was carried out in the experimental area of the Center of Agrarian and Environmental Sciences of the Federal University of Maranhão, located in the city of Chapadinha in East Maranhense Mesoregion and Microregion of Chapadinha, in the state of Maranhão (3˚44'30''S, 43˚21'37''W and 105 m altitude). The climate is classified according to Köeppen as Aw tropical dry, with annual average temperature of 26.9˚C, 63% relative humidity and annual rainfall of 1670 mm according to the National Institute of Meteorology [
The predominant soil of the region is classified as Dystrophic Yellow Latosol, a sandy-loam texture [
Gritstone | Fine sand | Clay | Silt | Soil texture |
---|---|---|---|---|
25.80 g・kg−1 | 53.50 g・kg−1 | 8.60 g・kg−1 | 12.10 g・kg−1 | Sandy |
pH | MO | P resine | H + Al | K | Ca | Mg | SB | CTC | V% |
---|---|---|---|---|---|---|---|---|---|
CaCl2 | g・dm−3 | mg・dm−3 | -----------------------mmolc・dm−3---------------- | % | |||||
6.9 | 19.0 | 17.0 | 1.0 | 1.6 | 0.5 | 0.9 | 6.06 | 7.06 | 86.0 |
The experimental area was divided into 24 plots of 50 m2 (5 × 10 m), where corn was sown in January 2012, with spacing of 1 × 0.20 m, with five planting lines per plot, discarding 0.50 m of its extremities. The cultivar AG1051, an early-cycle double hybrid, was used. The fertilization was carried out based on the soil analysis and according to the recommendation for maize crop, except for the source of phosphorus (simple superphosphate), which were applied in the corn plots at different levels (0, 60, 70, 80, 90, 100 kg・ha−1 of P2O5) in order to evaluate its residual effect on the succession crop, cowpea.
They applied 18 kg・ha−1 of urea and 104 kg・ha−1 of potassium chloride and 72 kg・ha−1 of urea were applied in sowing at 25 days after emergence. The other cultural dealings were made as needed. Green maize was harvested at the beginning of June 2012 and, shortly thereafter, new soil samples were collected for quantification of nutrient contents expressed in
Afterwards, the opening of pits for the sowing of the cowpea, as a successive crop, was carried out on the corn straw. The cultivar BRS Guariba was used that has an indeterminate growth habit, short branches, semi-erect size and maturation cycle of 65 to 70 days. The experimental design was a randomized complete block design, containing six treatments and four replications, totaling 24 plots. The treatments consisted of doses of residual P from maize fertilization, as follows: 0, 60, 70, 80, 90 and 100 kg・ha−1 of P2O5.
The sowing fertilization for cowpea was recommended according to the soil analysis, which consisted only of potassium, in which 51.72 kg・ha−1 of potassium chloride were used in all plots. Nitrogen fertilization was excused due to soil organic matter content, which was found to be in an average of 19 g・dm−3, where it should only be carried out in newly deforested areas or in sandy soils with organic matter content less than 10 g・kg−1 [
Cowpea seeds were inoculated with turfous inoculant (concentration of 5 ×
Parameters | P residual em kg・ha−1 de P2O5 | |||||
---|---|---|---|---|---|---|
0 | 60 | 70 | 80 | 90 | 100 | |
M.O (g・dm3) | 20.0 | 17.0 | 19.0 | 19.0 | 21.0 | 18.0 |
pH | 4.8 | 5.8 | 5.2 | 4.8 | 5.1 | 5.3 |
H + Al | 29..0 | 15.0 | 26.0 | 28.0 | 24.0 | 19.0 |
K | 1.0 | 0.9 | 1.0 | 1.1 | 1.1 | 0.8 |
Ca | 15.0 | 31.0 | 22.0 | 18.0 | 19.0 | 21.0 |
Mg | 5.0 | 3.0 | 4.0 | 1.0 | 7.0 | 5.0 |
S.B | 21.0 | 34.9 | 27.0 | 20.1 | 27.1 | 26.8 |
CTC | 50.0 | 49.9 | 53.0 | 48.1 | 51.1 | 45.8 |
P (mg・dm−3) | 3.0 | 22.0 | 13.0 | 12.0 | 12.0 | 11.0 |
V (%) | 42.0 | 70.0 | 51.0 | 42.0 | 53.0 | 59.0 |
K/CTC (%) | 2.0 | 1.8 | 1.9 | 2.3 | 2.2 | 1.7 |
Mg/CTC (%) | 10.0 | 6.0 | 7.5 | 2.1 | 13.7 | 10.9 |
109 g−1 cells), which contained the strain SEMIA 5079 and SEMIA 5080 of Bradyrhizobium japonicum. The inoculation was carried out by pre-wetting the seeds with a sugar solution (0.1 g・ml−1 concentration), according to the manufacturer’s recommendation. Seeding was carried out soon after inoculation of the seeds, on June 11, 2012. During the crop cycle, a supplementary irrigation depth of 115 mm was applied to meet the crop water requirements, using a conventional sprinkler irrigation system with a flow rate of 3.6 m3・h−1. The applications were performed with three days watering and each application, with a blade of 6.8 mm.
Three plants were selected at random from each plot, which were identified with a red ribbon to perform the variables plant height (PH) and stem diameter (ST) at 15 and 30 DAE (days after the experience). Ten whole plants were collected in the experimental plot at 15 and 30 DAE to evaluate the following variables: main root length (MRL), fresh shoot mass (FSM), dry shoot mass (DSM), fresh root mass (FRM), and root dry mass (RDM); (NRP), nodule diameter (DN), fresh nodule mass (FNM) and nodule dry mass (NDM), as well as the number of secondary root nodules were analyzed.
To determine the leaf area, leaves of the last trefoiled were collected per plot at 15 and 30 DAE. The leaves were then scanned and analyzed by software image tool 3.0 [
The economic analysis of the evaluated treatments was carried out taking into consideration the economic return only of the costs with phosphate fertilization. Net Revenue (NR) was obtained by difference between Gross Revenue (GR) and Costs (C) (NR = GR − C), considering the local price of the simple superphosphate of US $229.44 per ton and the bag of cowpea of US $52.46.
Data were submitted were submitted to the normality test (Shapiro Wilk, P < 0.05), and to analysis of variance (ANOVA), according to the statistical model: Yij = μ + Bi + Fj + Eij, where: Yij is dependent variable; μ is the general mean, Bi is the effect of the ith block; Fk is the effect of the kth level of residual phosphorus and Eijk is the experimental error, assuming Eijk ~ NID (0, σ2), and compared by the Duncan test (coefficient of variation―CV < 50%) and Kruskal-Wallis test (non-parametric test) (CV > 50%) [
There was no influence of residual phosphorus doses for the plant height (PH) and main root length (MRL) variables at 15 and 30 days after emergence (AE) (
Residual effect of phosphate fertilizations under cowpea cultivation in the
Residual P (kg・ha−1 of P2O5) | PH (cm) | MRL (cm) | SD (cm) | LA (cm2) |
---|---|---|---|---|
15 DAE | ||||
0 | 10.82 a | 11.46 a | 0.39 b | 16.52 a |
60 | 11.46 a | 10.75 a | 0.48 a | 20.66 a |
70 | 11.76 a | 10.76 a | 0.48 a | 20.73 a |
80 | 12.25 a | 11.74 a | 0.44 ab | 18.68 a |
90 | 12.01 a | 16.92 a | 0.44 ab | 21.21 a |
100 | 11.36 a | 10.95 a | 0.48 a | 16,16 a |
CV% | 7.67 | 42.68 | 11.69 | 19.21 |
30 DAE | ||||
0 | 20.30 a | 14.92 a | 0.58 a | 29.64 b |
60 | 20.86 a | 14.43 a | 0.63 a | 36.86 a |
70 | 21.48 a | 18.08 a | 0.63 a | 33.29 ab |
80 | 25.42 a | 14.76 a | 0.62 a | 34.86 ab |
90 | 22.92 a | 15.95 a | 0.55 a | 31.43 ab |
100 | 20.86 a | 19.24 a | 0.57 a | 32.66 ab |
CV% | 15.55 | 20.38 | 15.96 | 12.93 |
Means followed by the same letter in the column do not differ by Duncan test at the 5% meaningfulness level. CV: coefficient of variation.
state of Paraíba, with doses of 0 to 160 kg・ha−1 of P2O5 in maize (predecessor) [
As for the diameter of the stem (SD), it is possible to observe that the doses of 60, 70 and 100 kg・ha−1 of residual P2O5 promoted higher SD at 15 DAE, differing (P < 0.05), however, only the treatment without this nutrient, but at 30 DAE, all treatments analyzed were statistically the same. This was due to the higher availability of P (
Evaluating P doses of up to 210 kg・ha−1, [
In fact, the results obtained for SD at 15 and 30 DAE can be explained by the high solubility of the phosphate fertilizers. It is known that when very soluble sources are used in tropical soils, which have a high P fixing capacity, they are converted into forms unavailable to plants, and thus have their efficiency reduced with time [
There was no difference (P < 0.05) for leaf area (LA) at 15 DAE, but at 30 DAE the residual dose of 60 kg・ha−1 of P2O5 promoted higher LA, but did not differ, however, from other treatments, except the control. The low concentration of P (3 mg・dm−3) in the control treatment may be the justification for the lower LA found, since it is known that phosphorus is an element related to photosynthesis of plants [
When analyzing the variable fresh mass of the aerial part (MAP) (
The results obtained with the cultivar BRS-Paraguaçu, indicate that the highest values of APDM with the fertilization of 70 kg・ha−1 of P2O5 in the forms of single superphosphate are similar to those found in the present research [
The requirements of P may be relatively higher for the production of roots than for the production of leaves [
Residual P (kg・ha−1 of P2O5) | FSM (g) | DSM (g) | FRM (g) | RDM (g) |
---|---|---|---|---|
15 DAE | ||||
0 | 9.04 a | 1.26 ab | 0.75 a | 0.15 a |
60 | 9.59 a | 1.12 ab | 0.69 a | 0.13 a |
70 | 10.96 a | 1.28 ab | 0.74 a | 0.16 a |
80 | 8.73 a | 1.30 ab | 0.62 a | 0.15 a |
90 | 10.96 a | 1.43 a | 0.65 a | 0.15 a |
100 | 7.96 a | 0.99 b | 0.50 a | 0.14 a |
CV% | 21.20 | 21.30 | 27.31 | 15.12 |
30 DAE | ||||
0 | 40.81 a | 8.12 b | 2.97 b | 0.15 b |
60 | 42.71 a | 9.84 ab | 3.75 ab | 0.13 b |
70 | 48.63 a | 12.24 a | 3.38 ab | 0.16 b |
80 | 54.59 a | 8.95 b | 4.26 a | 0.15 b |
90 | 43.96 a | 7.55 b | 3.25 ab | 0.15 b |
100 | 42.71 a | 7.61 b | 3.32 ab | 0. 75 a |
CV% | 21.13 | 19. 53 | 21.10 | 26.56 |
Means followed by the same letter in the column do not differ by Duncan test at the 5% meaningfulness level. CV: coefficient of variation.
because P is closely related to root growth [
In relation to the nodule analysis (
Residual P* | MRN | NSRN | MRND | FRNM | DMR | |||
---|---|---|---|---|---|---|---|---|
15 DAE | ||||||||
0 | 0.5 | 0.1 | 0.07 | 0.03 | 3.6E−03 | |||
(0.0 - 1.0) a | (0.0 - 1.0) b | (0.00 - 0.45) a | (0.00 - 0.07) b | (0.00 - 0.01) b | ||||
60 | 1.50 | 17.66 | 0.26 | 0.27 | 0.06 | |||
(0.0 - 4.6) a | (0.6 - 39.6) a | (0.00 - 0.3) a | (4.0E−03 - 0.3) a | (2.3E−03 - 0.13) a | ||||
70 | 1.3 | 13.5 | 0.1 | 0.15 | 0.04 | |||
(1.0 - 3.0) a | (3.0 - 15.3) a | (0.02 - 0.13) a | (4.0E−03 - 0.04) ab | (4.0E−03 - 0.04) ab | ||||
80 | 0.3 | 7.5 | 0.12 | 0.09 | 0.02 | |||
(0.0 - 2.6) a | (1.6 - 11.6) ab | (0.0 - 0.2) a | (0.01 - 0.13) ab | (3.8E−03 - 0.03) ab | ||||
90 | 1.17 | 15.8 | 0.1 | 0.19 | 0.04 | |||
(0.0 - 3.6) a | (0.0 - 2.6) a | (0.00 - 0.33) a | (0.00 - 0.26) ab | (0.00 - 0.07) ab | ||||
100 | 0.5 | 8.8 | 0.17 | 0.15 | 0.04 | |||
(0.0 - 9.6) a | (1.0 - 21.6) a | (0.0 - 0.2) a | (3.0E−03 - 0.5) ab | (1.0E−03 - 0.03) ab | ||||
30 DAE | ||||||||
0 | 0.0 | 0.0 | 0.0 | 0.27 | 0.01 | |||
(0.0 - 0.0) a | (0.0 - 1.6) b | (0.0 - 0.0) a | (0.00 - 0.97) a | (0.00 - 0.21) a | ||||
60 | 0.5 | 5.0 | 0.1 | 0.31 | 0.10 | |||
(0.0 - 2.6) a | (1.3 - 41.0) ab | (0.0 - 0.3) a | (0.03 - 1.37) a | (0.01 - 0.51) a | ||||
70 | 0.5 | 7.0 | 0.05 | 0.42 | 0.06 | |||
(0.0 - 6.3) a | (0.0 - 20.0) ab | (0.0 - 0.0) a | (0.00 - 0.84) a | (0.00 - 0.17) a | ||||
80 | 0.0 | 7.8 | 0.0 | 0.61 | 0.09 | |||
(0.0 - 0.0) a | (2.0 - 9.0) a | (0.0 - 0.5) a | (0.06 - 0.96) a | (0.01 - 0.11) a | ||||
90 | 0.5 | 3.3 | 0.12 | 0.25 | 0.07 | |||
(0.0 - 2.0) a | (0.0 - 23.0) ab | (0.01 - 0.75) a | (0.01 - 0.75) a | (6.0E−04 - 0.14) a | ||||
100 | 1.0 | 4.5 | 0.09 | 0.26 | 0.04 | |||
(0.0 - 3.3) a | (0.0 - 8.6) ab | (0.00 - 0.53) a | (0.00 - 0.53) a | (0.00 - 0.11) a | ||||
Means followed by the same letter in the column do not differ from each other by the non-parametric analysis performed by the Kruskal-Wallis test at the 5% meaningfulness level. *kg・ha−1 of P2O5.
It is possible to observe that, in general, all treatments fertilized with phosphorus promoted a higher number of nodules in the secondary roots (NSR) at 15 and 30 DAE. The importance of this analysis is the close relationship between the efficiency of the N2 fixation process and the availability of P due to its participation in the symbiotic process. Several studies have already verified the effect of phosphate fertilization on growth and nodulation in leguminous [
It is known that P is an element able to increase the efficiency of nodulation and this happens because the biological fixation of N2 is a process that demands a great energy demand [
The nodulation of cowpea occurs adequately at doses of approximately 40 kg・ha−1 of P2O5 [
According to the results shown in
The treatments presented pods with a length between 21.61 cm and 24.32 cm, within commercial standards that is above 20 cm [
Residual P1 | NPP | PL (cm) | NGP |
---|---|---|---|
0 | 2.85 b | 21.61 b | 13.30 bc |
60 | 4.65 ab | 24.32 a | 15.18 a |
70 | 4.55 ab | 23.56 ab | 14.00 ab |
80 | 4.98 a | 23.16 ab | 13.60 ab |
90 | 4.78 ab | 23.32 ab | 13.80 ab |
100 | 4.33 ab | 22.20 ab | 11.90 c |
CV% | 27.17 | 5.88 | 7.19 |
Means followed by the same letter in the column do not differ by Duncan test at 5% meaningfulness level. CV: coefficient of variation. 1kg・ha−1 of P2O5.
a large number of flower abscission [
Linear correlation analysis found positive relationships between some analyzed variables; the plant height (PH) had a positive correlation (P < 0.05), with dry mass of root nodules (MRN), dry shoot mass (DSM), leaf area (LA) and grain yield to 15 DAE, which means that there is a correlation between these characteristics, that is, the highest response to a plant height variable, simultaneously, there will be increase for NDM, DMA, LA and PROD (
The number of nodules in the main root (NMR) showed a positive correlation with the number of nodules in the secondary root (NSR) (P < 0.05 and P < 0.01) and root dry mass (RDM) 05 and P < 0.01) at 15 and 30 DAE, respectively. It is seen that the larger the root system, the greater the amount of secondary roots and the greater the chance of nodule formation in these. Root nodulation is directly related to the supply of nutrients to the common bean, especially nitrogen. In the present study, secondary root nodulation (NRS) was more relevant for production, since it presented a positive correlation (P < 0.05) at 15 DAE and highly significant (P < 0.01) at 30 DAE (SM), it is worth noting that the dry mass of the nodules (DMN) showed a significant positive correlation with grain yield (PROD) at 30 DAE (
The pod length showed a positive correlation (P < 0.01) for the number of grains per pod and (P < 0.05) for the pod numbers, since the higher CV will condition the greater chance of grain development (
The residual dose of 80 kg・ha−1 of P2O5 promoted higher grain yield, around 393.5 Mg・ha−1 (
PH | MRL | MRN | SRN | DRM | NDM | DMA | LA | PROD | |
---|---|---|---|---|---|---|---|---|---|
AP | 1.00 | ||||||||
CRP | 0.02 | 1.00 | |||||||
NRP | −0.11 | 0.21 | 1.00 | ||||||
NRS | 0.21 | −0.23 | 0.44* | 1.00 | |||||
MSR | 0.02 | 0.02 | 0.67** | 0.86** | 1.00 | ||||
MSN | 0.50* | 0.23 | 0.05 | 0.00 | 0.02 | 1.00 | |||
MSPA | 0.49* | 0.31 | 0.05 | −0.03 | 0.00 | 0.71** | 1.00 | ||
AF | 0.49* | −0.03 | 0.07 | 0.27 | 0.19 | 0.42* | 0.44* | 1.00 | |
PROD | 0.44* | 0.01 | 0.13 | 0.51* | 0.39 | 0.03 | 0.04 | 0.18 | 1.00 |
*Significant at 5% probability by the t test; **Significant at 1% probability by F test.
AP | CRP | NRP | NRS | MRN | MSR | MSPA | AF | PROD | |
---|---|---|---|---|---|---|---|---|---|
AP | 1.00 | ||||||||
CRP | 0.19 | 1.00 | |||||||
NRP | 0.12 | 0.23 | 1.00 | ||||||
NRS | 0.32 | 0.14 | 0.62** | 1.00 | |||||
MSR | 0.18 | 0.00 | 0.47* | 0.85** | 1.00 | ||||
MSN | 0.45* | −0.03 | −0.13 | −0.11 | −0.16 | 1.00 | |||
MSPA | 0.57** | 0.12 | −0.22 | 0.00 | 0.06 | 0.62* | 1.00 | ||
AF | 0.55** | 0.02 | 0.29 | 0.70** | 0.67** | 0.37 | 0.42* | 1.00 | |
PROD | 0.24 | −0.19 | 0.27 | 0.55** | 0.45* | 0.21 | 0.22 | 0.47* | 1.00 |
*Significant at 5% probability by the t test; **Significant at 1% probability by F test.
PL | GP | PN | GY | |
---|---|---|---|---|
PL | 1 | |||
GP | 0.79** | 1 | ||
PN | 0.48* | 0.26 | 1 | |
GY | 0.33 | 0.2 | 0.47 | 1 |
*Significant at 5% probability by the t test; **Significant at 1% probability by F test.
Residual P (kg・ha−1 of P2O5) | Grain Productivity (Mg・ha−1)* | Net Revenue (US$) |
---|---|---|
0 | 120.48 c | 105.13 |
60 | 256.32 b | 210.73 |
70 | 256.37 b | 208.47 |
80 | 393.44 a | 326.26 |
90 | 295.82 ab | 238.42 |
100 | 189.37 bc | 142.85 |
Means followed by the same letter in the column do not differ by Duncan test at the 5% meaningfulness level. CV: coefficient of variation.
to the data [
The economic feasibility analysis seeks to identify the expected benefits in a given investment to put them in comparison with the investments and associated costs (
In general, grain yield in treatments with residual doses of P was not lower than that obtained in the large crop producing regions, and considerably higher (P < 0.05) than the treatment without addition of P, which presented a productivity of 57, 8% less than treatment with 100 kg・ha−1 dose of P2O5 and 227% less than the productivity obtained with the 80 kg・ha−1 dose treatment of P2O5.
Thus, it can be inferred that in some cases, it is worth making use of the residual phosphorus applied in the predecessor crop, since the use of residual fertilization can favor the fertilizer economy, reduce the leaching of salts to the water table and, consequently, the contamination of rivers and lakes, promoting greater environmental sustainability.
The cultivation of cowpea in previously cultivated areas is feasible, in order to take advantage of the residual phosphate fertilization in the Cerrado of East of Maranhão, being the dose of phosphorus applied in the predecessor crop (maize) corresponding to 80 kg・ha−1 of P2O5 recommended, because it promotes higher yields of cowpea beans and profit margin.
The authors thank the Fundação de Amparo à Pesquisa e ao DesenvolvimentoCientífico e Tecnológico do Maranhão (FAPEMA) (Foundation for Research and Scientific and Technological Development of Maranhao) and the Center for Agricultural and Environmental Sciences of the Universidade Federal do Maranhão (UFMA) (Federal University of Maranhão).
Gaspar, J. da C., Furtado, M.B., Silva, W.J. dos S., Reis, I. dos S., Machado, N.A.F., de Farias, M.F., Furtado, J.L.B., de Andrade, H.A.F., Sobral, R. da S., Parra-Serrano, L.J., Rodrigues, K. de M. and Silva-Matos, R.R.S. (2018) Impacts of Residual Phosphorus on the Production of Cowpea in the Cerrado Region. American Journal of Plant Sciences, 9, 645-658. https://doi.org/10.4236/ajps.2018.94051