We conducted two field experiments to investigate combined effects of organic and inorganic fertilizers on nitrogen use and recovery efficiencies of hybrid rice (Palethwe-1) during dry and wet seasons, 2015. Four levels of inorganic fertilizer (0%, 50%, 75%, and 100% NPK), based on recommended rates of 150 kg N ha - 1 , 70 kg P2O5 ha - 1 , and 120 kg K2O ha - 1 , were used with cow manure, poultry manure, and vermicompost (5 t·ha - 1 each) in a split-plot design with three replicates. In both seasons, with 50% NPK, the N uptake level achieved with poultry manure was similar to that obtained with 75% and 100% NPK. The greatest N use, internal, agronomic N use, and recovery efficiencies were obtained with 50% NPK + poultry manure, but were similar to those obtained from cow manure and vermicompost subplots. As the amount of applied N from organic and inorganic fertilizer increased, the N use efficiency and related parameters decreased, due to similar yields among plots with different NPK application levels. Poultry manure resulted in the highest significant correlations between applied N and N accumulation, followed by cow manure and vermicompost, in both seasons. Neither chemical fertilizer nor organic manure alone led to optimum N use and N recovery efficiencies. The combination of 50% inorganic fertilizer (75 kg N ha - 1 ) and poultry manure (5 t·ha - 1 ) enhanced the N uptake, the N use and recovery efficiencies of hybrid rice. Cow manure (5 t·ha - 1 ) in combination with 75% inorganic fertilizer (112.5 kg N ha - 1 ) was an adequate substitute for reduced chemical fertilizer usage. Therefore, this study highlighted combined application of inorganic fertilizers and organic manures had the benefits not only in reducing the need for chemical fertilizers but also in improving N uptake by hybrid rice (Palethwe-1) leading to the better environment.
Currently, global crop production requires inputs of roughly 105 million tons of nitrogen (N), 20 million tons of phosphorus (P), and 23 million tons of potassium (K) [
Rice constitutes one of the most important staple foods for over half of the world’s population [
N is required for all non-legume crops on all soil types. In rice cultivation, it is usually applied in the form of inorganic fertilizer, whereas the straw, which is used for animal feed, is seldom returned as the fertilizer to rice fields. This has contributed to a progressive decline in important soil components in agricultural land, a situation worsened by soil-intensive cropping and the use of high doses of chemical fertilizers with little or no addition of organic manure. Consequently, previous fertile soils have become degraded, with limited organic matter and nutrient contents.
In Myanmar, as in other areas of the world, inappropriate fertilization and the excessive use of N fertilizer have resulted in considerable N losses through ammonia (NH3) volatilization and leaching [
Glaser et al. [
As demonstrated by Zadeh [
In rice, NUE is the main parameter used to determine nutrient uptake [
Thus, not surprisingly, annual rice production is facing a sustainability problem due to production practices that often result in the indiscriminate use of chemical fertilizers and pesticides [
Two field experiments were conducted on the farm of the Department of Agro- nomy, Yezin Agricultural University, Nay Pyi Taw Division, Myanmar (19˚10'N, 96˚07'E) to study the combined effects of various organic manure and inorganic fertilizer levels on NUE and NRE of hybrid rice (Palethwe-1) (
A split-plot design with three replications was used in the two field experiments. The size of each experimental plot was 3 × 5 m. The distances maintained between two replications and two plots were 2 and 0.5 m, respectively. Plots treated with inorganic fertilizers (NPK), applied in proportions of 0%, 50%, 75%, and 100% based on the recommended rates of 150 kg N ha−1, 70 kg P2O5 ha−1, and 120 kg K2O ha−1, were designated as the main plots. Plots treated with organic manures (cow manure, poultry manure, and vermicompost; 5 t・ha−1 each) and the no organic manure control, were designated as subplots. The position of each treatment was not changed between the first and second field experiment.
The land was irrigated so as to be easily plowed, subsequently harrowed, and then divided into four parts (as the main plot area) for the application of the different inorganic fertilizers levels. Each main plot was divided into four subplots. Double bunds were created to prevent seepage between adjacent plots. The full amount of organic manure was applied during land preparation. Inorganic fertilizer consisting of urea (as the N source) and muriate of potash (K2O source) was applied in three equal splits: one third before transplanting (baseline), one third at the active tillering stage, and one third at the panicle initiation stage. The full amount of triple superphosphate (P2O5 source) was applied as the basal dose.
Baseline soil samples were collected from eight locations in the experimental field at a depth of 0 - 15 cm using a soil sampling tube (5 cm diameter). The samples were spread out, air dried at room temperature, crushed by hand, sifted through a 2-mm mesh sieve, and then analyzed for their physical and chemical properties.
The soil pHH2O (1:5, soil:water) in mass ratio was measured using a pH meter F-51 HORIBA and the 4A1-1:5 soil water suspension method [
The cow manure, poultry manure, and vermicompost were placed in a temperature controlled oven and their nutrient contents then extracted for gravimetric analysis [
The rice cultivated in this study was the hybrid rice (Oryza sativa L.) variety Palethwe-1. It is widely used in Myanmar because of its high potential yield. Rice seeds obtained from the farm of Yezin Agricultural University were soaked in water for 24 h and then incubated at 25˚C for 48 h. The sprouted seeds were sown on a well-prepared seed bed using the wet bed method of the International Rice Research Institute. The water level was gradually increased depending on the seedling height. On day 23, the seedlings were transplanted to hills with a spacing of 20 × 20 cm and two seedlings per hill. During the growing season, irrigation as well as insect, disease, and weed control were performed according to standard cultural practices. The plants were harvested at crop maturity, ~92 days after transplantation, in both seasons.
Samples obtained from two hills in each plot 2 - 3 cm above ground were oven-dried at 70˚C for 48 h and ground to a fine powder. The N contents of the straw and grain in the samples were analyzed separately using the Kjaldehl distillation method [
The amount of applied N from the inorganic fertilizer and the organic manures was calculated. Based on the total NU of rice plants, NUE [
No. | Sample | Moisture (%) | Organic carbon (%) | Total % (oven dry basic) | |||
---|---|---|---|---|---|---|---|
N | P2O5 | K2O | S | ||||
1. | Cowdung manure | 18.54 | 13.39 | 1.05 | 1.99 | 2.34 | 0.59 |
2. | Poultry manure | 33.03 | 24.73 | 2.83 | 4.90 | 4.67 | 0.53 |
3. | Vermicompost | 28.10 | 13.91 | 1.29 | 0.42 | 0.70 | 0.28 |
Source: Soil and Plant Analysis Laboratory, Soil Science Section, Soil Science, Water Utilization and Agricultural Engineering Division, Department of Agricultural Research (DAR).
and the internal efficiency (IE) [
Agronomic N use efficiency (AUE) [
The NRE [
The data were evaluated using an analysis of variance. Means comparison among treatments were subjected to Tukey’s HSD test at the 5% probability level. The analyses were carried out using STATISTIX 8 software (Analytical Software, Tallahassee, FL, USA).
The physicochemical properties of the surface (0 - 15 cm) soil at the experimental site are shown in
Characteristics | Value | Rating |
---|---|---|
pH (1:5 soil-water) Available N (mg∙kg−1) Available P (mg∙kg−1) Available K (mg∙kg−1) Organic matter (%) CEC (cmol(+)/kg) Texture, % silt, % sand, % clay Soil textural class | 6.6 73.0 20.0 77.0 1.8 8.0 19.64, 72.57, 7.79 Sandy loam | Neutral Medium Medium Low Low Low |
Source: Soil and Plant Analysis Laboratory, Soil Science Section, Soil Science, Water Utilization and Agricultural Engineering Division, Department of Agricultural Research (DAR).
tion of the soil data based on a previous report of the Federal Ministry of Agriculture and Natural Resources [
The differences in NU as a function of inorganic fertilizer level and organic manure type were significant (p < 0.01). The interaction effect of the combined application of organic and inorganic fertilizers was significantly higher (p < 0.01) during the dry than the wet season (
During the dry season, NU was highest (162.21 kg・ha−1) in the combined 100% inorganic fertilizer + poultry manure plot (I100-Op) (
The trends in the NU during the wet season were similar (
Probability p value | ||||||||||
---|---|---|---|---|---|---|---|---|---|---|
Source | Dry season (2015) | Wet season (2015) | ||||||||
NU | NUE | IUE | AUE | NRE | NU | NUE | IUE | AUE | NRE | |
Inorganic fertilizer (I) | ˂0.0001 | 0.0001 | ˂0.0001 | 0.0040 | 0.0006 | ˂0.0001 | 0.0001 | 0.0063 | 0.0034 | 0.0617 |
Organic manures (O) | ˂0.0001 | 0.0026 | 0.1637 | 0.0001 | ˂0.0001 | ˂0.0001 | 0.0575 | 0.0001 | ns | 0.0010 |
I × O | 0.0001 | 0.0018 | ˂0.0001 | 0.0004 | 0.0006 | 0.0001 | ns | 0.0001 | ns | ns |
CV % | 4.88 | 7.70 | 9.11 | 13.77 | 10.16 | 5.87 | 7.11 | 5.71 | 16.77 | 12.14 |
NU = Nitrogen uptake, NUE = nitrogen use efficiency, IUE = internal use efficiency, AUE = agronomic nitrogen use efficiency, NRE = nitrogen recovery efficiency, ns = non-significant difference.
Ov-treated subplots, even at the highest inorganic fertilizer level (I100-Ov, 120.13 kg・ha−1).
In both seasons, the differences in NUE among inorganic fertilizer levels and among organic manures were significant (p < 0.01 and p < 0.05, respectively) (
I75-Ov subplots [75.45, 77.34, and 81.02 kg grain ha−1 (kg N applied)−1, respectively], but also lower in the I75-O0 subplot [80.30 kg grain ha−1 (kg N applied)−1]. The application of any of the manures in combination with 100% NPK during the dry season resulted in NUEs that were lower than those of any of the other tested conditions.
During the wet season, all of the NUEs obtained in the combined applications of organic and inorganic fertilizer were very similar to those of the dry season. The highest NUE was that of the I50-Op subplot [99.00 kg grain ha−1 (kg N applied)−1] followed by the I50-Ov [96.51 kg grain ha−1 (kg N applied)−1] and I50-Oc [91.00 kg grain ha−1 (kg N applied)−1] subplots. The NUE achieved with the various combinations of organic and inorganic fertilizer correlated negatively with the amount of applied inorganic fertilizer (
The IE, defined as the grain yield per total N uptake, was significantly (p < 0.01) influenced by both organic and inorganic fertilizer application during both seasons. The interaction between organic and inorganic fertilizers was also significant (
During the wet season, the IE of the I50-Op subplots was also the highest [85.00 kg grain (kg NU)−1], with a slightly lower value in I75-Op subplots [76.00 kg grain (kg NU)−1]. An increase in the amount of inorganic fertilizer to I75 and I100 resulted in similar yields in the fields treated with the organic manures (
The AUE was significantly influenced by inorganic fertilizer application (p < 0.01) during both seasons, but was influenced by organic manure only during the dry season (
The application of inorganic fertilizer significantly influenced the NRE, both during the dry (p < 0.01) and the wet (p < 05) seasons. The differences in the NRE achieved with the different manures were also significant (p < 0.01). The NRE was highest in the I50-Op subplot [51.25 kg additional NU (kg N applied)−1] but the differences compared to the other subplots were not significant with values of 45.63, 43.66, 44.61, and 43.95 kg additional NU (kg N applied)−1 for I50-Oc, I75-Oc, I75-Op, and I100-Op, respectively. Generally, the NRE decreased steadily with increasing amounts of N from organic and inorganic fertilizers. In the sandy loam soil, the high losses of N in I100-Oc, I100-Op, and I100-Ov resulted in lower NREs of 32.96, 43.95, and 35.08 kg additional NU (kg N applied)−1, re-
spectively) (
During the wet season, the highest NUE was also in the I50-Op subplot [48.06 kg additional NU (kg N applied)−1], in accordance with its higher NU. Nonetheless, similar NREs of 43.98 and 37.96 kg additional NU (kg N applied)−1 were obtained in the I50-Oc and I50-Ov subplots, respectively. Because of the high N losses, the NREs in the I75 plus manures and I100 plus manures subplots were lower. In the subplots treated with 100% inorganic fertilizer alone, the NRE was lower [24.11 kg additional NU (kg N applied)−1] than in the I50-Op [48.06 kg additional NU (kg N applied)−1] subplot (
This study compared the effect of inorganic fertilizer application, as recommended by Myanmar’s DAR for the hybrid rice variety Palethwe-1 (150 kg N ha−1, 70 kg P2O5 ha−1, 120 kg K2O ha−1), with that of the combined application of organic and inorganic fertilizers in terms of NU, NUE, and related parameters. Generally, hybrid rice with a high yield potential has high nutrients requirements. However, the use of large amounts of inorganic fertilizers, including N fertilizers [
Our study showed that the combined application of organic and inorganic fertilizer effectively enhances the NUE of hybrid rice, as the maximum NUE was achieved in the I50-Op subplot in both seasons. The higher NU achieved with I50-Op resulted in a larger yield, as a high NUE was generated with less N loss, presumably due to the higher nutrient availability and major nutrient content of Op. In fact, this manure had the highest nutrient content of all tested manures. Its use as a soil amendment for agricultural crops was previously shown to provide appreciable quantities of all important plant nutrients [
The correlation coefficient (R2) between applied N and N accumulation among the subplots treated with organic and inorganic fertilizer was significant (p < 0.05) (
Inorganic fertilizers | Cow manure | Poultry manure | Vermicompost | |
---|---|---|---|---|
Dry season | ||||
Wet season |
y = N accumulation (kg・ha−1), x = Applied N (kg・ha−1), ** indicates significance at p = 0.01, * indicates significance at p = 0.05.
cow manure or vermicompost [
However, in the subplots receiving inorganic fertilizer alone, the correlation between applied N and N accumulation was relatively weak, reflecting N losses from the sandy loam soil. Together, these results recommend the use of combined applications of organic and inorganic fertilizer, especially Op, to maximize NU and therefore the yield of hybrid rice (Palethwe-1).
The IE of Palethwe-1 hybrid rice was highest in the I50-Op subplot, because of the higher grain yield and higher NU. With the application of increasing amounts of inorganic fertilizer, the IE decreased, as the yields of the manure-treated I50, I75, and I100 subplots were similar. The lower NU of the Oc and Ov subplots accounted for their lower IEs, which were still higher than the IE in the subplots treated with inorganic fertilizer alone (I50-O0, I75-O0, and I100-O0). Liu et al. [
A lower AUE was obtained only for 100% inorganic fertilizer alone whereas the values with I100-Oc, I100-Op, and I100-Ov were similar. Although the amount of applied N from organic and inorganic fertilizer was maximized, the yields of the different subplots were similar. Thus, half the amount of inorganic fertilizer resulted in the maximum AUE in both seasons when poultry manure was also applied. This result demonstrates that the maximum yield of hybrid rice depends on the application of the optimal amount of applied N from organic as well as inorganic fertilizer. In addition to N, organic manure provides important micronutrients and increases the CEC of soil, which in turn improves nutrient availability and, in combination with inorganic fertilizers, enhances plant growth and grain yield [
In our experiments, 5 t∙ha−1 of each manure (cow manure, poultry manure, and vermicompost) was combined with different amounts of inorganic fertilizer. Both cow and poultry manures are readily available in Myanmar and are thus economical for the country’s farmers. The use of vermicompost is less wide spread because of inadequate production and the high cost. Efficient and inexpensive methods of organic and inorganic fertilizer application are important for Myanmar farmers. Our results demonstrate that 50% inorganic fertilizer applied in combination with manures, especially poultry manure, is sufficient to provide high but economical hybrid rice yields. Specifically, in the central dry zone of Myanmar, the use of I50 (75 kg N ha−1) + Op (5 t poultry manure ha−1) will greatly enhance the NU, NUE, and NRE of hybrid rice. If poultry manure is not easily available, cow manure (5 t∙ha−1) plus I75 (112.5 kg N ha−1) is the next best alternative for reducing chemical fertilizer use. Antil and Singh [
This study was supported by Japanese Government (MEXT) Scholarship Program 2016-2019, Japan. We thank to Dr. Kyaw Kyaw Win (Professor) and Kumudra Win Mg (M. Agr. Sc), Department of Agronomy, Yezin Agricultural University, Myanmar for their contribution to this research.
I have disclosed that there are no conflicts of interest regarding publication of this article.
Moe, K., Mg, K.W., Win, K.K. and Yamakawa, T. (2017) Effects of Combined Application of Inorganic Fertilizer and Organic Manures on Nitrogen Use and Recovery Efficiencies of Hybrid Rice (Palethwe-1). American Journal of Plant Sciences, 8, 1043-1064. https://doi.org/10.4236/ajps.2017.85069