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Given the increasing dairy and poultry industries, cowdung (CD) and poultry manure (PM) might become alternative sources of nitrogen (N) for rice production in South Asia. A field experiment was conducted during dry season (November-April) in Gazipur, Bangladesh. The experiment aimed to evaluate N use efficiency (NUE) in rice under varying sources of N application. Six treatments—1) N-control; 2) optimum dose of nitrogen (164 kg N ha^{﹣1}) from urea; 3) 50% N from urea and 50% N from CD; 4) 50% N from urea and 50% N from PM; 5) 100% N from CD; and 6) 100% N from PM— were compared. Two mega varieties—BRRI dhan28 and BRRI dhan29—were used as test crops. In BRRI dhan28, the urea treatment had the highest agronomic use efficiency (AUE), utilization efficiency (UE) and partial factor productivity (PFP) followed by urea PM treatment and absolute PM treatment. In BRRI dhan29, the urea PM treatment had the highest AUE followed by absolute urea treatment while the urea PM treatment gave the highest UE and PFP followed by urea treatment and urea CD treatment. The absolute PM treatment gave the highest physiological efficiency (PE) followed by absolute urea treatment in BRRI dhan28. In BRRI dhan29, the absolute PM treatment had the highest PE followed by urea treatment and urea PM treatment. The absolute PM treatment had the highest agro physiological efficiency (APE) both in BRRI dhan28 and BRRI dhan29. Based on this finding, it is concluded that the practice of integrated use of organic and chemical fertilizer has the scope to reduce chemical fertilizer and also contribute to increasing nitrogen use efficiency.

Nitrogen is one of the most yield-limiting nutrients in rice production around the world [

Worldwide, N recovery efficiency for cereal production is approximately 33%. For lowland rice in the tropics, recovery efficiency is 30% - 50% of applied N depending on season, yield level, the rate and timing of N application [

Increasing cropping intensity with modern rice varieties has enhanced nutrient mining from the soil because nutrient removal has exceeded annual replacement, even if the national recommended fertilizer doses are applied. Moreover, farmers in Bangladesh are mainly concerned about the application of N fertilizer and tend to neglect P and K fertilizers for rice cultivation because their application often does not produce the yield advantages of the past [

Organic manures and chemical fertilizers are both important for rice cultivation. Organic manures improve the physical condition of the soil and supply limited quantities of plant nutrients through enhanced microbial activity [

Sustainability in crop yield and soil health could be achieved by the application of mineral fertilizers along with organic manures. Benefits of organic manures like farm yard manure, green manures, poultry manure and vermicompost are well-known but the availability is reducing day by day. These organic manures not only are good sources of nutrients but also improve the physical structure of the soil. Apart from containing NPK, these also contain small amounts of trace elements especially boron, copper, iron, sulphur, zinc and with fair quantity of growth promoting substances. Integrated nutrient management involving both the organic and inorganic source is, imperatively, essential to realize higher yield potential.

Integrated nutrient management―the combined use of chemical fertilizers and organic amendments―can be a measure to maintain sustainable soil productivity in tropical countries such as Bangladesh. It is well recognized that soil organic matter is an important fertility parameter, which largely determines soil quality. The average organic matter content of Bangladesh soil is about 1.0%. Under tropical climates increasing organic matter to a high level is not possible [

Cow dung is a good source of different plant nutrients particularly NPKS and judicious application of cow dung along with inorganic nutrients might be helpful to obtain a good economic return as well as provided favorable conditions for subsequent crops [

Poultry manure is an excellent source of promising organic fertilizer, which is cost effective to the farmers. Nowadays, industrialization of poultry is a vital sector of national economy in Bangladesh and byproduct of this industry, i.e., manure and poultry liter may be used as good source of organic matter with a view to develop an agronomically and economically suitable combination of organic and inorganic fertilizers for improving soil health and rice production. It has a high nutritional value for plant growth [

The field experiment was conducted at the experimental farm of the Bangladesh Rice Research Institute (BRRI), Gazipur, Bangladesh, located at 23˚59'N latitude, 90˚24'E longitude. The site is about 35 m above the mean sea level and has a subtropical climate, which is strongly influenced by the southwestern monsoon. It belongs to agro-ecological zone (AEZ) number 28 known as Madhupur Tract. The average annual rainfall is 2000 mm with more than 80% of it occurring from mid-June to the end of September. Mean temperature is lowest (15˚C) in January and highest (30˚C) in May.

The soil of the experimental field is Chhiata clay loam, a member of the fine, hyperthermic Vertic Endoaquept [^{−}^{1} (0.5 M NaHCO_{3} extracted), exchangeable potassium (K) 0.17 meq/100g soil (Neutral 1.0 N NH_{4}OAc extracted), available sulfur (S) 20 mg∙kg^{−}^{1} [Ca(H_{2}PO_{4})_{2} extracted], and available zinc (Zn) 2.8 mg∙kg^{−}^{1} (0.01 N HCl extracted).

In Bangladesh context two popular mega winter rice varieties BRRI dhan28 and BRRI dhan29 were grown in the experimental field under fully irrigated conditions during boro’2010-2011 (November-April) season. BRRI dhan28 is a short duration high yielding boro variety (growth duration 145 days) and BRRI dhan29 is a long duration high yielding boro variety (growth duration 160 days). These two varieties were transplanted in first week of January with 40 - 45 days old seedlings and harvested in May. Two/three rice seedlings were transplanted maintaining 20 ´ 20 cm spacing. The seed rate for rice was 30 kg∙ha^{−}^{1}. The experiment was conducted in a randomized complete block design with four replications. Unit plot size was 5 ´ 4 m. All plots were surrounded by soil levees 30 cm high to avoid N contamination between plots. After transplanting the seedlings, intercultural operations like weeding, irrigation and control of pest were done as and when necessary for better growth and development of rice plants. At maturity the crop was harvested manually at 15 cm above ground level, however, 16 hills from each plot were harvested at the ground level for measuring yield components and straw yield. The grain yield was recorded at 14% moisture content and straw yield as oven dry basis following standard procedures as described by [^{−}^{1}, weight of 1000 grains, harvest index and sterility (%) were calculated by following standard procedures as described by [

Harvest index (HI) was computed by dividing the grain yield by the total dry matter (grain yield + straw yield) and was expressed as percentage as follows:

Sterility was computed by dividing the number of unfilled spikelets by the total number of spikelets (filled grains + unfilled spikelets) and was expressed as percentage as follows:

Rice plants from 5 m^{2} area of the middle of each plot were harvested and threshed. The grains were dried in sunlight and winnowed before weighing and yield was adjusted to 14% moisture content and was converted into t∙ha^{−}^{1}. Six treatments were consisted as follows: 1) N control (0 kg N ha^{−}^{1}), 2) Optimum dose of nitrogen (164 kg∙ha^{−}^{1}) from urea 3) 50% N from urea and 50% N from cowdung (CD), 4) 50% N from urea and 50% N from poultry manure (PM), 5) 100% N from CD and 6) 100% N from from PM.

Nitrogen was top dressed as urea in three equal splits: 20, 35 and 50 days after transplanting (DAT) for BRRI dhan28 and 20, 35 and 55 DAT for BRRI dhan29. Phosphorus, K, S and Zn were applied as triple super phosphate, muriate of potash, gypsum and zinc sulphate, respectively, during final land preparation. The CD and PM were applied on a dry weight basis and mixed well with the soil, by manual digging, about two weeks before transplanting of rice. The CD was collected from the BRRI cattle shed and PM was collected from a nearby poultry farm. Nutrient concentrations in CD and PM were determined. The N, P, K and S concentration in CD (oven dry basis) were 0.85%, 0.33%, 0.52% and, 0.08% and those in PM were 2.28%, 1.03%, 1.20% and 0.24%, respectively.

Nitrogen was determined from the collected plant samples. Grain and straw samples from each plot (200 mg) were taken and separately oven dried at 65˚C over night to grind in a grinding machine. The ground sample was digested in concentrated H_{2}PO_{4} and total N concentration was determined by micro Kjeldahl method [

Nitrogen use efficiencies were calculated using the following formulas [

Agronomic efficiency (AE). It is expressed as difference in grain yield between fertilized and unfertilized plot divided by the quantity of nutrient applied. It is expressed as kg∙kg^{−}^{1}.

where G_{f} is the grain yield of the fertilized plot (kg), G_{u} is the grain yield of the unfertilized plot (kg), and N_{a} is the quantity of N applied (kg).

Physiological use efficiency (PE). The physiological efficiency is the difference in biological (grain + straw) yield between fertilized and unfertilized plots over difference in nutrient uptake between fertilized and unfertilized plots. It is expressed as kg∙kg^{−}^{1}.

where Y_{f} is the total biological yield ( grain plus straw) of the fertilized plot (kg), Y_{u} is the total biological yield of the unfertilized plot (kg), N_{tf} is the nutrient accumulation of the fertilized plot (kg), and N_{tu} is the nutrient accumulation of the unfertilized plot (kg).

Agrophysiological efficiency (APE). The difference in grain yield between fertilized and unfertilized plots divided by the difference in nutrient uptake in them is known as agrophysiological efficiency (APE).

where G_{f} is the grain yield of the fertilized plot (kg), G_{u} is the grain yield of the unfertilized plot (kg), N_{tf} is the N accumulation by straw and grains in the fertilized plot (kg), N_{tu} is the N accumulation by straw and grains in the unfertilized plot (kg). The unit of agrophysiological efficiency is kg∙kg^{−}^{1}.

Apparent recovery efficiency (ARE). It states that the percentage of the applied nutrient that is apparently absorbed the crop.

where N_{f} is the N accumulation by the total biological yield (grain plus straw) in the fertilized plot (kg), N_{u} is the N accumulation by the total biological yield (grain plus straw) in the unfertilized plot (kg), and N_{a} is the quantity of N applied (kg).

Utilization efficiency (UE). The product of physiological efficiency and aparent recovery efficiency is known as utilization efficiency (UE). Essentially, the UE is dimensionless.

Partial factor productivity (PFP). The grain yield per quantity of nutrient applied, is considered as partial factor productivity (PFP). It is also unitless.

Internal use efficiency of applied nitrogen (IUE). It is calculated using the following formula:

where, GY is the grain yield (kg∙ha^{−}^{1}) and UN is the total N uptake (kg∙ha^{−}^{1}).

Reciprocal of Internal use efficiency (RIUE): It is the reverse calculation of IUE.

Analysis of variance (ANOVA) of the measured parameters was performed and the treatment means were compared using Least Significant Difference (LSD) at the 5% level of probability [

Nitrogen sources (N) and variety (V) interactions showed significant effect (P < 0.01) on tiller production at maturity. The individual effects of N and V for tiller production was also significant (P < 0.01) (^{2} in BRRI dhan28 and BRRI dhan29. In BRRI dhan28 the absolute urea treatment increased the number of tiller to 321 per m^{2} followed by urea + CD treatment (313 m^{−}^{2}). The urea + CD treatment and urea + PM treatment gave statistically similar number of tillers. The absolute CD treatment and the absolute PM treatment produced statistically similar number of tillers. The absolute urea treatment gave significantly higher tiller in comparison to that of absolute CD treatment and absolute PM treatment. In BRRI dhan29, the absolute urea treatment gave the highest number of tillers (383 m^{−}^{2}) followed by urea + PM treatment (373 m^{−}^{2}). The absolute PM treatment and urea + CD treatment gave statistically similar number of tillers. The absolute CD treatment gave significantly lower tiller production compared to that of urea + CD treatment. Irrespective of N sources, BRRI dhan29 produced significantly higher number of tillers compared to BRRI dhan28 except N control and absolute CD treatment. On the other hand, the absolute CD treatment produced of 261 and 256 tillers per m^{2} in BRRI dhan28 and BRRI dhan29, respectively.

Nitrogen sources (N) and variety (V) interactions for panicle production were significant (P < 0.01). The individual effect of N for panicle production was also significant (P < 0.01) (

Interaction of nitrogen sources (N) and variety (V) for grain yield demonstrated insignificant (P > 0.05) effect, however, both the variety and sources of N, individually, produced significant effect on the rice grain yield (P < 0.01). BRRI dhan29 out yielded BRRI dhan28 at all N treatments including the control and application of N through organic or inorganic sources increased grain yield dramatically in both the varieties (^{−}^{1} compared to 4.53 t∙ha^{−}^{1} in BRRI dhan29. The application of N through urea increased grain yield over the N control by about 2.89 t∙ha^{−}^{1} in BRRI dhan28 and 3.01 t∙ha^{−}^{1} in BRRI dhan29. Sharing the N between urea and CD decreased yield significantly in both the varieties compared

Nitrogen sources (N) (kg∙ha^{−1}) | Tiller m^{−2} (No.) | Panicle m^{−2} (No.) | Grain yield (t∙ha^{−1}) | Straw yield (t∙ha^{−1}) |
---|---|---|---|---|

BRRI dhan28 | ||||

Control | 224 | 214 | 3.80 | 4.22 |

Urea | 321 | 309 | 6.69 | 6.94 |

Urea + CD | 313 | 299 | 6.07 | 6.33 |

CD | 261 | 250 | 4.61 | 4.85 |

Urea + PM | 301 | 286 | 6.46 | 6.52 |

PM | 274 | 265 | 6.46 | 6.61 |

Avg. | 282 | 271 | 5.68 | 5.91 |

BRRI dhan29 | ||||

Control | 218 | 209 | 4.53 | 5.02 |

Urea | 383 | 361 | 7.54 | 7.73 |

Urea + CD | 361 | 346 | 7.35 | 7.66 |

CD | 256 | 243 | 5.63 | 5.76 |

Urea + PM | 373 | 347 | 7.63 | 7.94 |

PM | 362 | 346 | 7.10 | 7.32 |

Avg. | 326 | 309 | 6.63 | 6.91 |

LSD_{0.05} for N | 29.27 | 28.48 | 0.25 | 0.33 |

LSD_{0.05} for V | 16.90 | 16.44 | 0.15 | 0.19 |

LSD_{0.05} for N × V | 41.40 | 40.28 | NS | NS |

CV (%) | 9.5 | 9.7 | 4.0 | 5.0 |

NS: non-significant at the 0.05 probability levels.

to that obtained with urea. But the urea + CD treatment gave a yield advantage of 2.27 and 2.82 t∙ha^{−}^{1}, compared to control, in BRRI dhan28 and BRRI dhan29, respectively. When the entire N was applied solely through CD, the grain yield decreased to 4.61 and 5.63 t∙ha^{−}^{1} in BRRI dhan28 and BRRI dhan29, respectively. These yields were statistically lowest among the N treatments in both the varieties, however, significantly higher than that obtained with the inherent soil N. The urea + PM treatment gave similar yield to that of urea in both the varieties, however, BRRI dhan29 gave about 1.17 t∙ha^{−}^{1} higher yield than BRRI dhan28. The PM treatment gave similar yield to that with urea + PM in BRRI dhan28, but BRRI dhan29 gave significantly lower in PM than the urea + PM. About 0.73 t∙ha^{−}^{1} yield advantage with BRRI dhan29 compared to BRRI dhan28 explained the fact that the former variety has capacity of exploiting soil inherent N of about 10 kg more than the latter variety. Apparent N recovery (ANR) was higher for chemical N application compared to organic N treatments. [

The individual effect of nitrogen source (N) for straw yield was highly significant (P < 0.01) (^{−}^{1}) followed by absolute PM treatment (6.61 t∙ha^{−}^{1}) and urea + PM treatment (6.52 t∙ha^{−}^{1}). The absolute PM treatment and absolute CD treatment gave the straw yield of 6.61 t∙ha^{−}^{1} and 4.85 t∙ha^{−}^{1}, respectively. The absolute PM treatment gave significantly higher straw yield than that of absolute CD treatment. On the other hand, absolute urea treatment gave significantly higher straw yield (6.94 t∙ha^{−}^{1}) than that of urea + CD treatment (6.33 t∙ha^{−}^{1}). The urea + CD treatment and urea + PM treatment gave statistically similar straw yield (6.33 t∙ha^{−}^{1} and 6.52 t∙ha^{−}^{1}, respectively). In BRRI dhan29, the urea + PM treatment gave higher straw yield (7.94 t∙ha^{−}^{1}) followed by urea treatment (7.73 t∙ha^{−}^{1}) and urea + CD treatment (7.66 t∙ha^{−}^{1}). The absolute PM treatment gave significantly lower straw yield (7.32 t∙ha^{−}^{1}) in comparison to urea + PM treatment (7.94 t∙ha^{−}^{1}). The absolute CD treatment gave significantly lower straw yield (5.76 t∙ha^{−}^{1}) compared to absolute PM treatment (7.32 t∙ha^{−}^{1}). On the other hand, urea + CD treatment gave significantly higher straw yield (7.66 t∙ha^{−}^{1}) in comparison to absolute CD treatment (5.76 t∙ha^{−}^{1}). The urea + CD treatment and urea + PM treatment gave statistically similar straw yield. The lowest straw yield was obtained from N control treatment in both the varieties (^{−}^{1}) in comparison to BRRI dhan28 (4.22 t∙ha^{−}^{1}). In urea treatment, BRRI dhan28 and BRRI dhan29 gave the straw yield of 6.94 t∙ha^{−}^{1} and 7.73 t∙ha^{−}^{1}, respectively. Under this treatment BRRI dhan29 gave the highest straw yield in comparison to BRRI dhan28. Under urea + CD treatment and absolute CD treatment, BRRI dhan29 gave significantly higher straw yields in comparison to BRRI dhan28. Under urea + PM treatment, BRRI dhan29 also gave significantly higher straw yield compared to BRRI dhan28. A similar trend of straw yield was also observed in absolute PM treatment.

Nitrogen sources (N) and variety (V) interactions were significant (P < 0.05) for the number of grains per panicle. The individual effect of N for grains panicle^{−}^{1} was highly significant (P < 0.01) (^{−}^{1} compared to the CD. Similarly urea + PM and PM treatment increased grains per panicle in comparison to that in urea and urea + CD treatment. The difference in grains per panicle between BRRI dhan28 and BRRI dhan29 was larger in urea + CD, urea + PM and PM compared to that in urea treatment. Both the N control and CD treatment showed similar difference in grains per panicle between the two tested varieties, but the difference was larger in urea than in N control and CD treatment. In the N control and CD treatments, BRRI dhan29 gave 14 and 13 more grain than the BRRI dhan28. In the urea treatment, the difference was 23, while in other treatments BRRI dhan29 gave 34 - 37 more grains per panicle than in BRRI dhan28.

Nitrogen sources (N) × variety (V) interactions were insignificant for 1000-grain weight (P > 0.05). The individual effect of N was also insignificant (P > 0.05) for 1000-grain weight (

In BRRI dhan28, the higher sterility (%) was obtained from urea treatment followed by urea + CD treatment and

Nitrogen source (N) (kg∙ha^{−1}) | Grains panicle^{−1} | 1000 grain wt (g) | Sterility (%) | Harvest index |
---|---|---|---|---|

BRRI dhan28 | ||||

Control | 78 | 22 | 6.20 | 0.44 |

Urea | 90 | 22 | 17.52 | 0.45 |

Urea + CD | 79 | 22 | 16.34 | 0.45 |

CD | 87 | 22 | 10.02 | 0.45 |

Urea + PM | 86 | 22 | 15.58 | 0.46 |

PM | 88 | 22 | 14.12 | 0.46 |

Avg. | 85 | 22 | 13.30 | 0.45 |

BRRI dhan29 | ||||

Control | 92 | 23 | 21.81 | 0.44 |

Urea | 113 | 24 | 18.79 | 0.46 |

Urea + CD | 113 | 24 | 21.63 | 0.45 |

CD | 100 | 24 | 25.09 | 0.46 |

Urea + PM | 123 | 24 | 18.77 | 0.45 |

PM | 123 | 22 | 17.54 | 0.46 |

Avg. | 111 | 24 | 20.61 | 0.45 |

LSD_{0.05} for N | 9.55 | NS | NS | 0.005 |

LSD_{0.05} for V | 5.51 | 0.74 | 2.02 | NS |

LSD_{0.05} for N × V | 13.50 | NS | 4.94 | NS |

CV (%) | 9.6 | 5.6 | 20.3 | 1.2 |

NS: non-significant at the 0.05 probability levels.

urea + PM treatment. The urea + PM treatment and absolute PM treatment gave statistically similar sterility (%). The absolute PM treatment gave significantly higher sterility (%) compared to absolute CD treatment. All the N treatments gave significantly higher sterility (%) in comparison to N control treatment. A different scenario was observed in BRRI dhan29. In BRRI dhan29, the absolute CD treatment gave the highest sterility followed by N control treatment and urea + CD treatment. The urea treatment, urea + PM treatment and absolute PM treatment produced statistically similar sterility. The absolute CD treatment gave significantly higher sterility compared to absolute PM treatment. Regardless of N sources BRRI dhan29 produced higher sterility than the BRRI dhan28. Under urea + CD treatment, BRRI dhan29 gave significantly higher sterility compared to BRRI dhan28. A similar scenario was also observed in absolute CD treatment. But under urea treatment, BRRI dhan28 and BRRI dhan29 gave statistically similar sterility. Under urea + PM treatment BRRI dhan29 produced higher sterility compared to BRRI dhan28. A similar scenario was also observed in absolute PM treatment (

In both the tested varieties (BRRI dhan28 and BRRI dhan29) the harvest index (HI) varied from 0.44 to 0.46. The N control plots gave the lowest harvest index in both the varieties. The application of N increased HI slightly. In BRRI dhan28, the urea + PM treatment and absolute PM treatment gave the higher HI followed by absolute urea treatment, urea + CD treatment and absolute CD treatment. In BRRI dhan29, the absolute urea treatment, absolute CD treatment and absolute PM treatment gave the higher HI (0.46) followed by urea + CD treatment and urea + PM treatment (0.45) (

A relationship between dry matter at harvest and grain yield was determined in BRRI dhan28 and BRRI dhan29. Grain yield increased significantly (P < 0.01) and quadratically with increasing dry matter in both the varieties. The quadratic regression equation (Y = −0.0x^{2}+ 3.1x − 7427.9 for BRRI dhan28 and Y = 0.00x^{2} + 0.90x − 706.24 for BRRI dhan29) can explain 99% of the relationship for BRRI dhan28 (R^{2} = 0.99) and 98% of the relationship for BRRI dhan29 (R^{2} = 0.98). Maximal grain yields of about 6690 kg∙ha^{−}^{1} were achieved at about 7214 kg∙ha^{−}^{1} of dry matter production in BRRI dhan28, with a harvest index of about 0.46 and 7630 kg∙ha^{−}^{1} were achieved at about 7983 kg∙ha^{−}^{1} of dry matter production in BRRI dhan29, with a harvest index of about 0.46 (

Nitrogen (N) × variety (V) interactions and the individual effect of V for straw nitrogen uptake (SNUP), grain nitrogen uptake (GNUP) and total nitrogen uptake (TNUP) were insignificant (P > 0.05). The individual effect of N was significant (P < 0.01) for SNUP, GNUP and TNUP (^{−}^{1}) followed by urea + CD treatment (36 kg∙ha^{−}^{1}), absolute CD treatment (35 kg∙ha^{−}^{1}) and absolute PM treatment (34 kg∙ha^{−}^{1}). The urea + PM treatment had the highest N uptake in rice grain (66 kg∙ha^{−}^{1}) followed by urea + CD treatment (62 kg∙ha^{−}^{1}), urea treatment (60 kg∙ha^{−}^{1}) and absolute PM treatment (55 kg∙ha^{−}^{1}). The N control treatment had the lowest N uptake both in rice straw and rice grain (^{−}^{1}) followed by urea treatment (98 kg∙ha^{−}^{1}) and urea + CD treatment (98 kg∙ha^{−}^{1}). The urea treatment, urea + CD treatment and absolute PM treatment gave statistically similar TNUP. The N control treatment had the lowest TNUP (^{−}^{1} of which 64% accumulated in rice grain and the rest 36% in

Nitrogen source (N) (kg∙ha^{−1}) | SNUP (kg∙ha^{−1}) | GNUP (kg∙ha^{−1}) | TNUP (kg∙ha^{−1}) |
---|---|---|---|

BRRI dhan28 | |||

Control | 16 | 29 | 45 |

Urea | 38 | 60 | 98 |

Urea + CD | 36 | 62 | 98 |

CD | 35 | 49 | 84 |

Urea + PM | 38 | 66 | 104 |

PM | 34 | 55 | 89 |

Average | 33 | 54 | 87 |

NHI | 0.63 | ||

BRRI dhan29 | |||

Control | 18 | 30 | 48 |

Urea | 38 | 66 | 104 |

Urea + CD | 39 | 73 | 112 |

CD | 34 | 56 | 91 |

Urea + PM | 33 | 76 | 109 |

PM | 32 | 61 | 93 |

Average | 32 | 60 | 92 |

NHI | 0.65 | ||

LSD_{0.05} for N | 7.61 | 11.99 | 18.30 |

LSD_{0.05} for V | NS | NS | NS |

LSD_{0.05} for N × V | NS | NS | NS |

CV (%) | 23.0 | 20.7 | 20.1 |

NS: non-significant at the 0.05 probability levels.

rice straw. Under urea treatment, TNUP was 98 kg∙ha^{−}^{1} of which 61% accumulated in rice grain and the rest 39% remained in rice straw. Under urea + CD treatment, TNUP was 98 kg∙ha^{−}^{1} of which 63% N uptake was observed in rice grain and 37% N uptake was in rice straw. Under absolute CD treatment, TNUP was 84 kg∙ha^{−}^{1} of which 58% N uptake was observed in rice grain and the rest 42% N uptake was in rice straw. Similarly, in urea + PM treatment and absolute PM treatment, TNUP was 104 kg∙ha^{−}^{1} and 89 kg∙ha^{−}^{1} of which 63% and 62% N uptake was observed in rice grain and the rest 37% and 38% was in rice straw, respectively (^{−}^{1}) followed by absolute urea treatment (38 kg∙ha^{−}^{1}) and absolute CD treatment (34 kg∙ha^{−}^{1}). The absolute CD treatment, urea + PM treatment and absolute PM treatment gave statistically similar N uptake in rice straw. The N control treatment had the lowest N uptake in rice straw (18 kg∙ha^{−}^{1}) (^{−}^{1}) followed by urea + CD treatment (73 kg∙ha^{−}^{1}) and urea treatment (66 kg∙ha^{−}^{1}). The urea treatment, absolute PM treatment and absolute CD treatment gave statistically similar N uptake in rice grain. The N control treatment had the lowest N uptake in rice grain (30 kg∙ha^{−}^{1}) (^{−}^{1}) followed by urea + PM treatment (109 kg∙ha^{−}^{1}) and urea treatment (kg∙ha^{−}^{1}). The absolute CD treatment and absolute PM treatment gave statistically similar TNUP. The N control treatment gave the lowest TNUP (48 kg∙ha^{−}^{1}) (^{−}^{1} of which 62% N uptake was observed in rice grain and the rest 38% N uptake was in rice straw under N control treatment. In urea treatment, TNUP was 104 kg∙ha^{−}^{1} of which 63% N uptake was observed in rice grain and the rest 37% N uptake was in rice straw. In urea + CD treatment, TNUP was 112 kg∙ha^{−}^{1} of which 65% N uptake was observed in rice grain and the rest 35% N uptake was in rice straw. In absolute CD treatment, TNUP was 91 kg∙ha^{−}^{1} of which 62% N uptake was occurred in rice grain and the rest 38% N uptake was observed in rice straw. In urea + PM treatment, TNUP was 109 kg∙ha^{−}^{1} of which 70% N uptake was observed in rice grain and the rest 30% was remained in rice straw. In absolute PM treatment, TNUP was 93 kg∙ha^{−}^{1} of which 66% N uptake was observed in rice grain and the rest 34% N uptake was in rice straw. Irrespective of N treatments, average TNUP in BRRI dhan28 was 87 kg∙ha^{−}^{1} of which 62% N uptake in rice grain and the rest 38% N uptake was in rice straw. Similarly in BRRI dhan29, average TNUP was 92 kg∙ha^{−}^{1} of which 65% N uptake was observed in rice grain and the rest 35% N uptake was in rice straw (

Application of 164 kg N ha^{−}^{1} through different sources influenced nitrogen use efficiency. In BRRI dhan28, the urea treatment had the highest AE (18 kg∙kg^{−}^{1}) followed by urea + PM treatment (16 kg∙kg^{−}^{1}) and absolute PM treatment (16 kg∙kg^{−}^{1}). The AE of urea + CD treatment was significantly lower in comparison to urea treatment, urea + PM treatment and absolute PM treatment. The absolute CD treatment had the lowest AE (5 kg∙kg^{−}^{1}). It was probably due to slow mineralization of CD in comparison to urea and PM. In BRRI dhan28, the average AE was 14 kg grain produced per kg N applied across N sources. In BRRI dhan29, the urea + PM treatment had the highest AE (19 kg∙kg^{−}^{1}) followed by absolute urea treatment (18 kg∙kg^{−}^{1}). The urea + CD treatment gave significantly higher AE in comparison to absolute CD treatment. The urea + CD treatment and absolute PM treatment gave similar AE. The absolute CD treatment had the lowest AE (7 kg∙kg^{−}^{1}). In BRRI dhan29, the average AE was 15 kg grain produced per kg N applied across N sources. Under urea + CD treatment, BRRI dhan29 gave significantly higher AE in comparison to BRRI dhan28. Under absolute urea treatment and absolute PM treatment BRRI dhan28 and BRRI dhan29 gave statistically similar AE.

Under absolute CD treatment and urea + PM treatment, BRRI dhan29 gave significantly higher AE in comparison to BRRI dhan28. The average agronomic efficiency (AE) was 14 kg∙kg^{−}^{1} (i.e. 14 kg grain produced per kg N applied) in BRRI dhan28 and 15 kg∙kg^{−}^{1} in BRRI dhan29 across N sources. The use of urea solely or in conjunction with poultry manure gave comparatively higher AE than those of CD. Agronomic efficiency is usually greater at the quick mineralized material than slow mineralized material of N source. Poultry manure has a higher nutrient content and more rapid mineralization rate compared to other animal manures [^{−}^{1}) followed by absolute urea treatment (117 kg∙kg^{−}^{1}) (^{−}^{1}). In BRRI dhan28, the average PE was 94 kg biological yield per unit of N accumulated across N sources. In BRRI dhan29, the absolute PM treatment had the highest PE (167 kg∙kg^{−}^{1}) followed by urea treatment (131 kg∙kg^{−}^{1}) and urea + PM treatment (119 kg∙kg^{−}^{1}). The absolute PM treatment gave significantly higher PE in comparison to urea + CD treatment. The absolute CD treatment had the lowest PE (48 kg∙kg^{−}^{1}). In BRRI dhan29, the average PE was 110 kg biological yield per unit of N accumulated across N sources. In BRRI dhan28, the absolute PM treatment had the highest agro physiological efficiency (APE) (75 kg∙kg^{−}^{1}) followed by absolute urea treatment (61 kg∙kg^{−}^{1}). In absolute PM treatment, APE was 75 kg grain produced per kg of N accumulated in the grain and straw whereas in urea treatment 61 kg grain produced per kg of N accumulated in the grain and straw. All the N treatments gave statistically similar APE except absolute CD treatment. The absolute CD treatment had the lowest APE (21 kg∙kg^{−}^{1}). In BRRI dhan29, the absolute PM treatment had the highest APE followed by urea treatment (69 kg∙kg^{−}^{1}) and urea + PM treatment (61 kg∙kg^{−}^{1}). The APE from absolute PM treatment was significantly higher in comparison to that of urea + CD treatment. The absolute CD treatment had the lowest APE was observed in (28 kg∙kg^{−}^{1}) (Ta- ble 4). [_{3} volatilization, or leaching [

In BRRI dhan28, the urea treatment had the highest utilization efficiency (UE) (34 kg∙kg^{−}^{1}) followed by urea + PM treatment (30 kg∙kg^{−}^{1}) and absolute PM treatment (31 kg∙kg^{−}^{1}). The urea treatment gave significantly higher UE in comparison to urea + CD treatment. The absolute CD treatment had the lowest UE (9 kg∙kg^{−}^{1}). In BRRI dhan29, the urea + PM treatment had highest UE (37 kg∙kg^{−}^{1}) followed by urea treatment (35 kg∙kg^{−}^{1}) and urea + CD treatment (33 kg∙kg^{−}^{1}). The urea + PM treatment gave significantly higher UE in comparison to absolute PM treatment. The absolute CD treatment had lowest UE (11 kg∙kg^{−}^{1}). Under urea + CD treatment and urea + PM treatment, BRRI dhan29 gave significantly higher UE in comparison to BRRI dhan28. Under urea

Nitrogen source (N) (kg∙ha^{−1}) | Agronomic efficiency (kg∙kg^{−1}) | Physiological efficiency (kg∙kg^{−1}) | Agro-physiological efficiency (kg∙kg^{−1}) | Apparent recovery efficiency (%) | Utilization efficiency (kg∙kg^{−1}) | Partial factor productivity (kg∙kg^{−1}) |
---|---|---|---|---|---|---|

BRRI dhan28 | ||||||

Urea | 18 | 117 | 61 | 33 | 34 | 41 |

Urea + CD | 14 | 85 | 44 | 33 | 27 | 37 |

CD | 5 | 38 | 21 | 24 | 9 | 28 |

Urea + PM | 16 | 84 | 45 | 36 | 30 | 39 |

PM | 16 | 144 | 75 | 27 | 31 | 39 |

Avg. | 14 | 94 | 49 | 31 | 26 | 37 |

BRRI dhan29 | ||||||

Urea | 18 | 131 | 69 | 34 | 35 | 46 |

Urea + CD | 17 | 87 | 45 | 39 | 33 | 45 |

CD | 7 | 48 | 28 | 26 | 11 | 34 |

Urea + PM | 19 | 119 | 61 | 37 | 37 | 47 |

PM | 16 | 167 | 86 | 27 | 30 | 43 |

Avg. | 15 | 110 | 58 | 33 | 29 | 43 |

LSD_{0.05} for N | 1.80 | 72.39 | 36.77 | NS | 4.30 | 1.66 |

LSD_{0.05} for V | 1.14 | NS | NS | NS | 2.72 | 1.05 |

LSD_{0.05} for N × V | NS | NS | NS | NS | NS | NS |

CV (%) | 12.1 | 69.2 | 66.8 | 37.7 | 15.2 | 4.1 |

NS: non-significant at the 0.05 probability levels.

treatment, absolute CD treatment and absolute PM treatment, BRRI dhan28 and BRRI dhan29 gave statistically similar UE (^{−}^{1} for flooded rice cultivar Metica1 i.e. 58 kg grain produced per kg N utilized across the N rates. [^{−}^{1}) followed by urea + PM treatment and absolute PM treatment (39 kg∙kg^{−}^{1}). The absolute PM treatment and urea + PM treatment gave significantly higher PFP (39 kg∙kg^{−}^{1}) in comparison to urea + CD treatment (37 kg∙kg^{−}^{1}). The absolute CD treatment gave the lowest PFP (28 kg∙kg^{−}^{1}). In BRRI dhan29, the urea + PM treatment gave the highest PFP (47 kg∙kg^{−}^{1}) followed by urea treatment (46 kg∙kg^{−}^{1}) and urea + CD treatment (45 kg∙kg^{−}^{1}) (^{−}^{1}). Application of same amount of N (164 kg∙ha^{−}^{1}) from different sources varied the N-supplying capacity due to mineralization capacity of the materials. PFP was 40 kg grain produced per kg N applied averaged over N sources and varieties. The lowest PFP produced from absolute CD treatment due to slow mineralization of CD. In BRRI dhan28, the N control treatment gave the highest internal use efficiency (IUE) (86 kg∙kg^{−}^{1}) followed by absolute PM treatment (75 kg∙kg^{−}^{1}) and urea treatment (71 kg∙kg^{−}^{1}). Urea + CD treatment and urea + PM treatment gave statistically similar IUE. The absolute CD treatment gave the lowest IUE (56 kg∙kg^{−}^{1}). In BRRI dhan29, the N control treatment gave the highest IUE (94 kg∙kg^{−}^{1}) followed by absolute PM treatment (81 kg∙kg^{−}^{1}) and absolute urea treatment (77 kg∙kg^{−}^{1}) (^{−}^{1}). Internal use efficiency was 72 kg∙kg^{−}^{1} averaged over N sources and varieties i.e. were 72 kg grain produced per

Nitrogen source (N) (kg∙ha^{−1}) | Internal use efficiency (IUE) (kg∙kg^{−1}) | Reciprocal of internal use efficiency (RIE) (kg∙kg^{−1}) |
---|---|---|

BRRI dhan28 | ||

Control | 86 | 12 |

Urea | 71 | 15 |

Urea + CD | 62 | 16 |

CD | 56 | 18 |

Urea + PM | 62 | 16 |

PM | 75 | 14 |

Avg. | 69 | 15 |

BRRI dhan29 | ||

Control | 94 | 11 |

Urea | 77 | 14 |

Urea + CD | 67 | 15 |

CD | 64 | 16 |

Urea + PM | 72 | 14 |

PM | 81 | 13 |

Avg. | 76 | 14 |

LSD_{0.05} for N | 15.02 | 2.91 |

LSD_{0.05} for V | NS | NS |

LSD_{0.05} for N × V | NS | NS |

CV (%) | 20.4 | 19.7 |

NS: non-significant at the 0.05 probability levels.

kg of total N uptake in the grain and straw. [^{−}^{1} and in BRRI dhan29, RIUE varied from 11 - 16 kg∙t^{−}^{1}. The N control treatments gave the lowest RIUE in both the varieties (^{−}^{1}) followed by urea + CD treatment (16 kg∙t^{−}^{1}) and urea + PM treatment (16 kg∙t^{−}^{1}). The absolute PM treatment, urea + PM treatment and urea treatment gave statistically similar RIUE. In BRRI dhan29, the absolute CD treatment gave the highest RIUE (16 kg∙t^{−}^{1}) followed by urea + CD treatment (15 kg∙t^{−}^{1}). The urea + PM treatment, urea treatment and absolute PM treatment gave statistically similar RIUE. [^{−}^{1} with full fertilization and 12.8 kg∙t^{−}^{1} in −N plots.

Managing the N application to rice is an essential to reduce N losses, improve N use efficiency and obtain higher yield. The use of urea solely or in conjunction with poultry manure gave comparatively higher N use efficiency than that of cowdung. Thus the doses of chemical fertilizer can be reduced by 50% by using poultry manure in dry season.

Amina Khatun,Hasina Sultana,Md. Sultan Uddin Bhuiya,Md. Abu Saleque, (2015) Nitrogen Use Efficiency of Low Land Rice as Affected by Organic and Chemical Sources. Open Access Library Journal,02,1-16. doi: 10.4236/oalib.1101327