Nitrogen uptake from organic manures and chemical fertilizer and yield of lowland rice

Transcription

1 Bull. Inst. Trop. Agr., Kyushu Univ. 39: 13-27, Nitrogen uptake from organic manures and chemical fertilizer and yield of lowland rice Amina Khatun 1) *, M. S. U. Bhuiya 2) and M. A. Saleque 3) Abstract 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 (Nov-April) in Chhiata clay loam soil. The experiment aimed to evaluate the effect of N from organic and inorganic sources on dry matter and N uptake pattern of rice. We compared (i) N-control, ii) Optimum dose of nitrogen (164 kg N/ha) from urea, iii) 50% N from urea and 50% N from CD, iv) 50% N from urea and 50% N from PM, v) 100% N from CD and vi) 100% N from PM. Two mega varieties and, were used as test crops. Application of N from urea, urea + PM and absolute PM increased dry matter significantly both in and. The combination of urea and PM, absolute urea and absolute PM gave greater N uptake compared to other treatments in different growth stages of rice. The urea + PM treatment gave similar yield to that of urea in both the varieties, however, gave about 1.17 t /ha higher yield than. The PM treatment gave similar yield to that with urea + PM in, but BRRI dhan29 gave significantly lower yield in PM than the urea + PM. Sole cowdung or poultry manure application produced significantly lower grain yield than urea + PM treatment and sole urea application. Because of insufficient mineralization of N from CD and PM, sole organic sources of N were not as good as combined use of organic and inorganic fertilizer amendments. Keywords: Rice, organic manure, chemical fertilizer, yield, N uptake. Introduction Rice (Oryza sativa L.) is the staple food for nearly half of the world s population, most of whom live in developing countries. The crop occupies one-third of the world s total area planted to cereals and provides 35-40% of the calories consumed by 2.7 billion people (Fageria and Baligar, 2001). Recent estimates showed that rice yield must be increased in Asia by about 25% from 2000 to 2020 with the increased yield of 4.9 t /ha from the present yield of 3.9 t /ha for meeting the demand of increased population (Dobermann et al., 2004). During this time, the total rice area of Bangladesh will shrink from million hectares to million ha and the rice yield will be needed to increase from 2.74 t /ha to 3.74 t /ha (Gomosta, 2004). In this context, there is no alternative other than yield increase per unit 1) Rice Farming Systems Division, Bangladesh Rice Research Institute, Gazipur 1701, Bangladesh 2) Professor, Department of Agronomy, Bangladesh Agricultural University, Mymensingh 2202, Bangladesh 3) Co-ordinator for Advanced Studies & Research, Bangladesh Rice Research Institute, Gazipur 1701, Bangladesh *Corresponding author: aminabrri@gmail.com

2 14 Amina Khatun et al. area. It is possible either by using improved technologies or developing management practices. Nitrogen is one of the most yield-limiting nutrients in rice production around the world (Fageria et al., 2008), and especially in tropical Asian soils and almost every farmer has to apply the costly N fertilizer to get a desirable yield of rice (Saleque et al., 2004). Judicious and proper use of fertilizers can markedly increase the yield and improve the quality of rice (Chaturvedi, 2005). 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. On decomposition, the organic matter is converted into humus in the soil. Humus promotes efficient use of nutrients supplied through fertilizers (Panda, 2006). Fertilizers, on the other hand, contain one or more plant nutrients in concentrated readily available forms. They can be so applied as to supply the nutrients needed by plants and thereby increase crop growth and yield (Panda, 2006). The use of organic manure in conjunction with or as an alternative to mineral fertilizer is receiving considerable attention (Singh and Gangwar, 2000; Saleque et al., 2004; Solaiman and Rabbani, 2006). The excessive application of chemical fertilizers has made it imperative that a portion of inorganic fertilizer is substituted by recycling organic waste. Organic manure has been proven to enhance efficiency and reduce the need for chemical fertilizers. Partial N substitution through the use of organic manure demonstrated significant superiority in yield over that produced by farmers (Singh and Gangwar, 2000). 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 (Saleque et al., 2004). Cowdung is a good source of different plant nutrients particularly NPKS and judicious application of cowdung along with inorganic nutrients might be helpful to obtain a good economic return as well as provided favorable conditions for subsequent crops (Solaiman and Rabbani, 2006). It is one of the potential sources of organic manure in Bangladesh. The application of cowdung in rice fields may reduce the requirement of chemical fertilizers. The doses of chemical fertilizer may be reduced by 33% for both dry and wet season by using cowdung and ash in the dry season (Saleque et al., 2004). The application of cowdung and ash not only supplemented chemical fertilizers but also contributed to the apparent nutrient balance. Apparently, there was accumulation of P and K due to the application of cowdung and ash along with two-third doses of recommended chemical fertilizers (Saleque et al., 2004). Another study observed that P buildup in soil due to the application of farmyard manure along with NPK chemical fertilizer (Ram, 1998; Sahoo et al., 1998). 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 by-product of this industry, for example manure and poultry litter 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 high nutritional value for plant growth (Zang et al., 1998; Ishak et al., 1999) and it is relatively cheaper source of both macronutrients and micronutrients. Availability of fertilizer at the right time is one of the major con-

3 Nitrogen uptake and yield of lowland rice 15 straints now a day for rice production in Bangladesh. The cost of fertilizer is also sky kissing. So, poultry litter could be used under such conditions to supplement plant nutrients for rice production because it contains good amount of available nutrients (Jacobs et al., 1996; Dobermann and Fairhast, 2000). Saleque et al. (2004) reported that the application of N fertilizer increased plant total N uptake, ranging from kg /ha for 10 rice genotypes in Bangladesh. Among macronutrients, nitrogen uptake is the highest with the exception of potassium (Fageria and Baligar, 2001). Furthermore, nitrogen recovery efficiency for lowland rice is less than 50% (Fageria and Baligar, 2005). Nitrogen uptake increased with the advancement of the age to the crop up to the flowering growth stage and decreased thereafter. This decrease is related to N translocation to grains at harvest (Fageria and Baligar, 2001). Under these circumstances, the present research works were designed with an attempt to evaluate cowdung and poultry manure as a alternate sources of N for rice production. Materials and Methods The field experiment was conducted at the experimental farm of the Bangladesh Rice Research Institute (BRRI), Gazipur, Bangladesh, located at / N latitude, / 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 25 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 0 C) in January and highest (30 0 C) in May. The soil of the experimental field is Chhiata clay loam, a member of the fine, hyperthermic Vertic Endoaquept (Saleque et al., 2004). The initial soil chemical properties at 0-15 cm soil depth were as follows: ph 6.1, organic matter 2.02%, total N content 0.07%, available phosphorus (P) mg /kg (0.5 M NaHCO 3 extracted), exchangeable potassium (K) 0.17 meq/100 g soil (Neutral 1.0 N NH 4 OAc extracted), available sulfur (S) 20 mg /kg [Ca(H 2 PO 4 ) 2 extracted], and available zinc (Zn) 2.8 mg /kg (0.01N HCl extracted), respectively. In Bangladesh, context two mega winter rice varieties and were grown in the experimental field under fully irrigated conditions during boro (November-April) season. is a short duration and high yielding boro variety (growth duration 145 days) and is a long duration and high yielding boro variety (growth duration 160 days). These two varieties were transplanted in first week of January with day-old seedlings and harvested in May. Two or three rice seedlings were transplanted maintaining cm spacing. The seed rate for rice was 30 kg /ha. 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 at 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 total straw yield data. The grain yield was recorded at 14% moisture content and straw yield as oven dry basis. Six treatments were consisted as follows: (1) N control (0 kg N /ha), (2) Optimum dose of nitrogen (164 kg /ha) from urea, (3) 50% N

4 16 Amina Khatun et al. 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 and 20, 35 and 55 DAT for. 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. To determine the physico-chemical properties at 0-15 cm soil depth of the experimental field, initial soil sample was collected and analyzed. Soil organic carbon was analyzed by Walkley-Black wet oxidation method and total nitrogen was determined by using Micro kjeldahl instrument. C/N ratio was calculated by dividing the results of organic carbon by total nitrogen. Soil ph in water was measured from a soil: water ratio (1: 2.5) using glass electrode method. All measurements of organic carbon, total nitrogen and soil ph were performed in triplicate. Dry matter weight of rice plant was determined at every 15 days from transplanting to maturity. Sixteen hills of rice plant from each plot were harvested at the base and the sample was oven dried at 70 C for 72 hours. Oven dry weight of the samples was converted to dry matter per m 2. 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 0 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 (Yoshida et al., 1976). Total N uptake was determined by the following formulae: % N in grain x Grain yield(kg/ ha) Nitrogen uptake by grain (kg/ ha) = 100 % N in straw x straw yield(kg/ha) Nitrogen uptake by straw (kg/ ha) = 100 Rice plants from 5 m 2 area of the middle of each plot were harvested at ground level and threshed. The grains were dried in sunlight and winnowed before weighing, the grain yield was adjusted to 14% moisture content and converted into t /ha. Analysis of variance (ANOVA) of the measured parameters was performed and the treatment means were compared using Duncan s multiple range test (DMRT) at the 5% level of probability. The yield and N uptake parameters were analyzed by ordinary least squares linear regression as reported by Dawe et al., (2000).

5 Nitrogen uptake and yield of lowland rice 17 Results and Discussion Dry matter production at different growth stages The individual effect of nitrogen sources (N) and variety (V) were statistically significant (p<0.01) but their interactions was not significant (p>0.05) in dry matter production at different growth stages (Table 1). Dry matter production at 15 and 30 DAT were not statistically varied. Dry matter ranged from 60 to 70 and 57 to 69 kg /ha at 15 DAT and; 84 to 93 and 86 to 99 at 30 DAT in and, respectively. At 45 DAT, the application of N increased dry matter in both the varieties. The dry matter varied from 146 to 429 kg /ha in and 164 to 503 kg /ha in. The magnitude of dry matter increase appeared the highest with urea + PM in and with urea alone in. Receiving the N from urea, the dry matter increased to 405 and 503 kg /ha in and, respectively. The application of N (50% from urea and 50% from CD) gave slightly lower dry matter than that obtained with urea in both the varieties. The absolute PM treatment produced significantly higher dry matter in comparison to urea + CD treatment. In BRRI dhan28, the application of urea alone increased the dry matter to 3040 kg /ha, while it raised to 3583 kg /ha in at 60 DAT. Receiving CD alone, the dry matter went down to 2141 and 2929 kg / ha in and, respectively. In fact, the produced the highest dry matter with urea + PM treatment at 60 DAT. The application of N solely through PM slightly reduced dry matter in with urea + PM treatment, but the reduction was significant in BRRI dhan29. At 75 DAT, dry matter production varied from 4541 to 7214 kg /ha in and from 5046 to 6876 kg /ha in (Table 1). gave the highest dry matter with urea treatment, while gave the highest dry matter with urea + PM treatment. With urea alone treatment, and produced dry matter of 7214 and 6748 kg /ha, respectively. The application of N through PM alone gave a dry matter of 6934 kg /ha in and 6408 kg / ha in (Table 1). At 90 DAT, a decreasing trend of dry matter production was found in all treatments in comparison to that of 75 DAT. Receiving the N through the urea treatment, it increased to 7004 and 7770 kg /ha in and, respectively. The urea+ CD treatment and urea+ PM treatment gave statistically similar dry matter both in and. The application of N through PM gave significantly higher dry matter in both the varieties compared with CD. Increase in dry matter production with urea, CD and PM alone or combination of CD or PM and urea was not countable at 15 and 30 DAT. The soil inherent supply of nitrogen was sufficient to maintain the N requirement of rice at low level of dry matter production. The varietal differences in dry matter between two varieties were obvious at 45 DAT. CD contributed about 77% of urea in BRRI dhan28 and 87% of urea in in dry matter production at 45 DAT. While PM contributed about 100% of urea in and 84% of urea in at 45 DAT. At 60 DAT, the varietal difference in dry matter was quite large ( kg /ha). produced higher biomass than the in all treatments. Increase in dry matter at given N treatment over the N control was larger in than in the. With urea + CD, CD and urea + PM treatments, showed a response of 496, 462 and 495 kg /ha, respectively, more than that of BRRI dhan28 in terms of dry matter production. Contrary to 60 DAT, at 75 DAT of the response of N to dry

6 18 Amina Khatun et al. Table 1. Dry matter production at different crop growth stages under different nitrogen sources in and Nitrogen source (N) (kg/ha) Days after transplanting Kg/ha Control Urea Urea + CD CD Urea + PM PM Avg Control Urea Urea + CD CD Urea + PM PM Avg LSD 0.05 for N NS NS LSD 0.05 for V NS NS NS LSD 0.05 for N V NS NS NS NS NS NS CV (%) NS non-significant at the 0.05 probability levels. matter production was higher in than in. The showed about 971 kg /ha more response of N to dry matter than that of the. Nitrogen uptake at different growth stages The effect of N and V was statistically varied individually, however, their interaction was not statistically different in relation to N uptake (p > 0.05). At 15 DAT, the N uptake varied from 0.90 to 1.20 kg /ha in and from 0.83 to 1.15 kg /ha in (Table 2). At this early growth stage the N treatment showed no significant effect on N uptake in. In, urea + PM treatment had higher N uptake than that of the control and urea + CD treatments. had lower N uptake than in all treatments except control. At 30 DAT, the N uptake varied from 1.16 to 1.72 and 1.21 to 1.86 kg /ha in and, respectively. The application of N from urea, urea + PM and absolute PM increased N uptake significantly in both varieties. At 45 DAT, application of urea increased N uptake to 6.67 kg/ha in and 7.19 kg /ha in BRRI dhan29, while urea + CD decreased N uptake to 4.85 and 5.44 kg /ha in and BRRI dhan29, respectively. The N uptake from the CD treatment was significantly lower than that of obtained with urea + CD treatment. In the CD treatment, showed significantly higher N uptake than that of at 45 DAT. The sole PM treatment gave significantly lower N uptake than the urea + PM treatment in both the varieties. Unlike the other N source treatments, showed slightly lower N uptake than receiving the sole PM treatment. The PM treatment of gave the highest N uptake, while urea + PM treatment gave the highest N uptake in

7 Nitrogen uptake and yield of lowland rice 19 (Table 2). Varietal difference in nitrogen uptake at 60 DAT increased dramatically compared to that observed at 45 DAT. Application of urea increased N uptake to 73.6 and 88.1 kg /ha in and, respectively. The urea + CD showed N uptake of 62.6 kg /ha in BRRI dhan28 and 71.8 kg /ha in, respectively. The sole CD treatment showed N uptake of 39 kg /ha in and 42.5 kg /ha in, respectively. The sole PM treatment gave slightly lower N uptake than that of the urea + PM treatment in but slightly higher in BRRI dhan29. showed significantly higher N uptake than that of receiving the urea + PM treatment. In the PM treatment, and gave 76.3 and 74.2 kg /ha N uptake, respectively (Table 2). At 75 DAT, gave significantly higher N uptake in comparison to under all the treatments except absolute CD and control treatments. Under absolute CD treatment and N control treatment, and gave statistically similar N uptake in dry matter. At 90 DAT, the urea treatment gave significantly higher N uptake than that of any other treatments in. In, the N uptake with PM and urea + PM treatment was not significantly higher than that of obtained with urea + CD. However, the application of N solely through urea gave the higher N uptake than that of organic and combination of organic and inorganic sources of N. An increasing trend was observed in N uptake with the advancement of crop age from 15 DAT to 75 DAT for both the varieties. But at 90 DAT, N uptake decreased in all the treatments compared to that of 75 DAT. At this growth stage, urea treatment gave significantly higher N uptake. The urea+ PM treatment, absolute PM treatment and urea+ CD treatment produced statistically similar Table 2. Nitrogen uptake at different growth stages under different nitrogen sources in and BRRI dhan29 Nitrogen source (N) (kg/ha) Days after transplanting Kg/ha Control Urea Urea + CD CD Urea + PM PM Avg Control Urea Urea + CD CD Urea + PM PM Avg LSD 0.05 for N LSD 0.05 for V NS NS NS NS LSD 0.05 for NS NS NS NS NS NS N V CV (%) NS non-significant at the 0.05 probability levels.

8 20 Amina Khatun et al. N uptake in dry matter. The N control treatment gave the lowest N uptake. In, the increase of N uptake at 30 DAT was 42% as compared to 15 DAT. At 45 DAT, the increase across the nitrogen treatments was 222% as compared to 30 DAT. At 60 DAT, the increase of N uptake was 1248% as compared to 45 DAT. At 75 DAT, the increase of N uptake was 59% as compared to 60 DAT. In, the increase of N uptake at 30 DAT was 52% as compared to 15 DAT. At 45 DAT, the increase of N uptake across the nutrient treatments was 265% as compared to 30 DAT. At 60 DAT, the increase of N uptake 1108% as compared to 45 DAT. At 75 DAT, the increase of N uptake was 21% as compared to 60 DAT. At 90 DAT, there were 54 and 14% decrease of N uptake as compared to 75 DAT in and, respectively. This decrease is related to N translocation to grains at harvest. Fageria and Baligar (2001) reported that more N was accumulated in grains than in dry matter at harvest. Dry matter yield depends on N accumulation in rice plant but up to a certain limit. After limit, there is no more increase in dry matter. The relationship between N uptake and dry matter production at 60 DAT was polynomial, which explains that the dry matter became independent of N uptake after a certain saturation point. It also explains that the accumulated N in the rice plant could have increased dry matter further, but certain other factors might have limited scope. Probably the genetic potential or the environmental condition was not conducive to utilize the accumulated N at the biochemical level. Relationship between N uptake and dry matter production A relationship between N uptake and dry matter production was determined at different growth stages (Fig.1.). At 15 DAT, poor linear relationship was observed between N uptake and dry matter production both in (R 2 = 0.38) but in the relationship was significant (R 2 = 0.80). The equation (Y = x for and Y = x for ) can explain only 38% of the relationship for but 80% of the relationship for BRRI dhan29. At 30 DAT, the N uptake showed weak relationship with dry matter production both in BRRI dhan28 and (R 2 = 0.55 for and R 2 = 0.44 for ). AT 45 DAT, regression analysis showed strong linear increases in dry matter production with the increase of N-uptake both in and (R 2 = 0.86 for and R 2 = 0.80 for BRRI dhan29). In, the highest N uptake (6 kg /ha) contributed to the highest dry matter production (429 kg /ha) and in, the highest N uptake (7.19 kg /ha) contributed to the highest dry matter production (503 kg /ha). At 60 DAT, dry matter showed a polynomial relationship with N uptake (R 2 = 0.92 for BRR dhan28 and R 2 = 0.79 for ). In, N uptake explained about 92% variation in dry matter, while in, it explained about 79% variation. At this growth stage based on regression equation, the lowest dry matter of 1372 and 1698 kg /ha in and corresponded to the N uptake of and kg /ha, respectively. Increasing the N uptake to and kg /ha increased the dry matter to 2141 and 2929 kg /ha in and, respectively. Similarly, the dry matter in both the varieties increased up to the N uptake of kg /ha in and kg /ha in. Beyond the maximum level of dry matter, the increase of N uptake poorly contributed to the dry matter production of rice at 60 DAT. At 75 DAT, regression analysis showed also polynomial relationship between N uptake and dry matter production (R 2 = 0.97 for and R 2 = 0.94 for ). The saturation

9 Nitrogen uptake and yield of lowland rice 21 point of the N uptake appeared as kg /ha in and kg /ha in at 75 DAT. At 90 DAT, dry matter yield showed stronger polynomial relationship with N uptake. The coefficient of determination between N uptake and dry matter in was at 0.98 and in was at The dry matter yield in at 90 DAT became independent of N uptake after kg /ha, while it was kg /ha in (Fig. 1.) DAT DAT DM yield (kg/ha) y = 19.78x R² = 0.38 y = 39.34x R² = N uptake (kg/ha) y = 13.94x R² = 0.55 y = 10.65x R² = N uptake (kg/ha) DM yield (kg/ha) y = 56.40x R² = 0.86 y = 51.11x R² = N uptake (kg/ha) 45 DAT DAT y = 27.32x R² = 0.87 y = 30.42x R² = N uptake (kg/ha) DM yield (kg/ha) 9000 BRI dhanr29 75 DAT y = 27.08x R² = 0.87 y = 25.06x R² = N uptake (kg/ha) DAT y = 55.93x R² = 0.92 y = 44.39x R² = N uptake (kg/ha) Fig. 1. Relationship between N uptake and dry matter production under different nitrogen sources in two rice varieties

10 22 Amina Khatun et al. Grain Yield Interaction effect of N and V was not significant (P>0.05) but their individual effect was significant (P<0.01) on grain yield (Table 3). out yielded at all N treatments. In the control plots, gave 3.80 t /ha compared to 4.53 t /ha in. The application of N through urea increased grain yield over the N control by about 2.89 t /ha in and 3.01 t / ha in. The treatment urea + CD decreased yield significantly in both the varieties compared to that obtained with urea. But the urea + CD treatment gave a yield advantage of 2.27 and 2.82 t /ha, compared to control, in and, respectively. When the entire N was applied solely through CD, the grain yield decreased to 4.61 and 5.63 t /ha in and BRRI dhan29, respectively. These yields were statistically lowest among the N treatments in both the varieties, however, significantly higher than that of the inherent soil N. The urea + PM treatment gave similar yield of urea in both the varieties, however, gave about 1.17 t /ha higher yield than BRRI dhan28. The PM treatment gave similar yield with urea + PM in, but gave significantly lower in PM than the urea + PM. Table 3. Grain and straw yield of two rice varieties as influenced by different nitrogen sources Nitrogen sources (N) (kg/ha) Grain yield Straw yield (t/ha) (t/ha) Control Urea Urea + CD CD Urea + PM PM LSD 0.05 for N LSD 0.05 for V LSD 0.05 for N V F-test (N) ** ** F-test (V) ** ** F-test (N V) NS NS CV(%) **, NS significant at the 0.01 probability levels and non-significant, respectively. Straw yield The individual effect of N and V was significant (P<0.01), but their interaction effect was not significant (P>0.05) for straw yield (Table 3). In, the absolute urea treatment gave the higher straw yield (6.94 t /ha) followed by absolute PM treatment (6.61 t /ha) and urea+ PM treatment (6.52 t / ha). The absolute PM treatment and absolute CD treatment gave the straw yield of 6.61 t /ha and 4.85 t / ha, 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) than that of urea+ CD treatment (6.33 t /ha). In, the urea+ PM treatment gave higher straw yield (7.94 t /ha) followed by urea treatment (7.73 t /ha) and urea+ CD treatment (7.66 t /ha). The absolute PM treatment gave significantly lower straw yield (7.32 t /ha) in comparison to urea+ PM treatment (7.94 t /ha). The urea+ CD treatment and urea+ PM treatment gave statistically similar straw yield

11 Nitrogen uptake and yield of lowland rice 23 (7.66 t /ha and 7.94 t /ha, respectively). In urea treatment, and gave the straw yield of 6.94 t /ha and 7.73 t /ha, respectively. Under urea+ CD treatment and absolute CD treatment, gave the straw yields of 6.33 t /ha and 4.85 t /ha, and gave the straw yields of 7.66 t /ha and 5.76 t /ha, respectively. Under these treatments, gave significantly higher straw yields in comparison to. Under urea + PM treatment, gave significantly higher straw yield (7.94 t /ha) compared to (6.52 t /ha). A similar trend of straw yield was also observed in absolute PM treatment. Mineralization of nitrogen The nitrogen mineralization of CD and PM was 28% and 76% in and 42% and 70% in. The nitrogen mineralization rate was higher in PM compared to CD (Table 4). Although the dependence of N mineralization on water content varies with temperature (Grundmann et al., 1995; Quemada and Cabrera, 1997), the spatial variability in water content is expected to be greater than that of soil temperature during the period of greatest crop demand for N. Therefore, emphasis is placed on the relation between N mineralization and soil water content (Drury et al., 2003). In the effects of organic matter and crop residue on microbial activity, temperature changes in the dynamics of the population of soil organisms were participated in N mineralization (Drury et al., 2003). Cowdung is slowly mineralized material and it releases the nutrients for a longer period. So, plants can not uptake sufficient nutrients according to their needs. Poultry manure (PM) released more nitrogen than cowdung (CD) due to its high nitrogen contents. A study showed that after 75 days of studies, CD application produced 2.70 mg /kg of NH + 4 -N and PM application produced 6.70 mg /kg of NH + 4 -N under anaerobic condition. Under aerobic condition, CD application produced 3.83 mg /kg of NO3 -N and PM application produced 6.86 mg /kg of NO3-N (BRRI, 2004). This result indicated to supply nutrients according to plant demands. Singh et al. (1987) concluded that application of PM incorporation with Table 4. Mineralization of nitrogen from different sources of nitrogen over N-control during crop growth cycle N-uptake Days after transplanting % Source Total mineralized Kg/ha N-uptake from urea N-uptake from CD N-uptake from PM N-uptake from urea+cd N-uptake from urea+pm N-uptake from urea N-uptake from CD N-uptake from PM N-uptake from urea+cd N-uptake from urea+pm

12 24 Amina Khatun et al. urea increased the concentration and accumulation of N in rice, which was 80% as efficient as urea N at all rates of applications. The use of PM as soil amendment would provide appreciable quantities of all the important plant nutrients (Sims and Wolf, 1994). Poultry manure gave the highest soil inorganic N, plant N and dry matter accumulation among the organic matter applications. Therefore, poultry manure can be a suitable fertilizer for rice production with environmental sustainability. Low dry matter, N accumulation and apparent N recovery were observed in cow manure and sole application of N which not provide the optimal rice production (Myint et al., 2010). Recently, Singh and Gangwar (2000), Khan et al.(2004) and Antil and Singh (2007) indicated that use of organic manures in conjunction with mineral fertilizer is very important for ensuring better soil health and sustaining crop productivity. Therefore, a mix application of manures with mineral N fertilizer might provide high inorganic N in soil and higher crop production. Relationship between nitrogen uptake and grain yield A relationship between N uptake and grain yield was determined at different growth stages (Fig. 2.). N uptake at 15 and 30 DAT poorly correlated to the grain yield of rice both in and. Nitrogen uptake at 45 DAT, showed a quadratic relationship y = x x for and y = x x for, respectively. At 60 DAT, the relationship between N uptake and grain yield was explained by the polynomial equation y = -1.2x x (R 2 = 0.99) in and y = -1.5x x (R 2 = 0.99) in BRRI dhan29 (Fig. 2.). The N uptake at 75 and 90 DAT also strongly influenced the rice yield. The relationship between N uptake and grain yield was also quadratic in both the varieties with R 2 = Nitrogen uptake at early growth stage (15 and 30 DAT) poorly explained the variation in grain yield. The N uptake by plant at the early growth stages also shows any good relationship with the dry matter production. The data explained that the plant at the early growth stages depended on the soil inherent N and the applied N poorly contributed to the dry matter production. However, the N uptake at 45 DAT showed strong relationship with the dry matter production as well as grain yield of rice. Soil N was not sufficient to meet plants demand at 45 DAT. Therefore, N application schedule at 45 DAT need to be observed very critically. Some old literatures suggest that the N uptake at the early growth stage contribute to the dry matter production. The N in plant before PI stage determines the number of spikelet per panicle. Our findings also suggest that the N uptake at 45, 60 and 75 DAT strongly influenced the grain yield of rice. Relationship between dry matter at harvest and grain yield A relationship between dry matter at harvest and grain yield was determined in and (Fig. 3.). Grain yield increased significantly (p<0.01) and quadratically with increasing dry matter in both the varieties. The quadratic regression equation can explain 99% of the relationship for (R 2 = 1.0) and 98% of the relationship for (R 2 = 0.98) as Y = -0.0 x x x for and Y = 0.00 x x for. Maximal grain yields of about 6690 kg /ha were achieved at about 7214 kg /ha of dry matter production in BRRI dhan28, with a harvest index of 0.46 and 7630 kg /ha were achieved at 7983 kg /ha of dry matter production in, with a harvest index of 0.46 (Fig. 3.).

13 Nitrogen uptake and yield of lowland rice 25 Grain yield (kg/ha) y = x R² = 0.52 y = x R² = N uptake (kg/ha) y = x R² = 0.73 y = x R 2 = N-uptake (kg/ha) 30 DAT Grain yield (kg/ha) y = x x R² =0.99 y = x x R² = N-uptake (kg/ha) 45 DAT y = -1.5x x R² = 0.99 y = -1.2x x R² = N-uptake (kg/ha) 60 DAT Grain yield (kg/ha) y = -1.1x x R² = 0.99 y = -0.4x x R² = N-uptake (kg/ha) 75 DAT y = -1.5x x R² = 0.99 y = -1.3x x R² = N-uptake (kg/ha) 90 DAT Fig. 2. Relationship between N uptake and grain yield in and

14 26 Amina Khatun et al BRI dhanr29 Grain yield (kg/ha) y = 0.00x x R² = 0.98 y = x x R² = DM yield (kg/ha) Fig. 3. Relationship between dry matter and grain yield production under different nutrient sources Conclusion An integrated application of PM with inorganic N fertilizer was appeared the best N management strategies for the great rice production. Acknowledgement The first author acknowledges the Strengthening of Breeder Seed Project, Bangladesh Rice Research Institute, Bangladesh, for providing scholarship and financial support for the study. References Antil, R.S. and Singh, M. (2007) Effects of organic manures and fertilizers on organic matter and nutrients status of the soil. Arch. Agron. Soil Sci. 53(5): BRRI (Bangladesh Rice Research Institute) (2004). Annual Report BRRI, Gazipur pp Chaturvedi, I. (2005) Effect of nitrogen fertilizers on growth, yield and quality of hybrid rice. J. Central European Agric. 6: Dawe, D., Dobermann, A., Moya, P., Abulrachmann, S., Singh, B., Lal, P., Li, S. Y., Lin, B., Panaullah, G. M., Sariam, O., Singh, Y., Swarup, A., Tan, P. S., Zhen, Q. X. (2000) How widespread are yield declines in long-term rice experiments in Asia? Field Crop Res. 66: Dobermann, A., Witt, C. and Dawe, D. (2004) Increasing productivity of intensive rice systems through site-specific nutrient management. Enfield, N. H. (USA) and Los Banos (The Philippines): Science Publishers. Intl. Rice Res. Inst. p Dobermann, A. and Fairhast, T. (2000) Rice: Nutrient disorders and nutrient management. Oxford Graphic Printers Ltd. pp Drury, C. F., Zhang, T. Q. and Kay, B. D. (2003) The non- limiting and least limiting water ranges for soil nitrogen mineralization. Soil Sci. Soc. Am. J. 67: Fageria, N. K. and Baligar, V. C. (2001) Lowland rice response to nitrogen fertilization. Commun. Soil Sci. Plant Ana.

15 Nitrogen uptake and yield of lowland rice 27 32(9): Fageria, N. K. and Baligar, V. C. (2005) Enhancing nitrogenuse efficiency in crop plants. Adv Agron. 88: Fageria, N. K., Santos, A. B. and Cutrim, V. A. (2008) Dry matter and yield of lowland rice genotypes as influence by nitrogen fertilization. J. Plant Nutr. 31: Gomosta, A. R. (2004) Emerging technologies for sustainable rice production in Bangladesh. Keynote presented in the 20 th HYV workshop, March 2004, BRRI, Gazipur. Grundmann, G. L., Renault, P., Rosso, L. and Bardin, R. (1995) Differential effects of soil water content and temperature on nitrification and aeration. Sci. Soc. Am. J. 59: Ishak, C. F., Bakar, R. A., Saud, H. M. and Abdullah, T. L. (1999) Application of sewage sludge from Indian water treatment plants. Agro Search. 6(1): Jacobs, R. D., Sloan, D. and Jacob, J. (1996) Cage layer manure: An important resource for land use. Fact sheet PS-9. Dairy and Poultry Sci. Dept., Cooperative Extn Service, Inst. Food Agril. Sci. Univ. Florida. USA. Khan, A. R., Chandra, C., Nanda, P., Singh, S. S., Ghorai, A. K. and Singh, S. R. (2004) Integrated nutrient management for sustainable rice production. Arch. Agron. Soil Sci. 50(2): Myint, A. K., Yamakawa, T., Kajihara, Y., Myint, K. K. M. and Zenmyo, T. (2010) Nitrogen dynamics in a paddy field fertilized with mineral and organic nitrogen sources. American-Eurasian J. Agric and Environ. Sci. 7: Panda, S.C. (2006) Production technology of crop management and integrated farming. p. 130., Agrobios (India), Agro house, Chopasani road, Jodhpur , India. Quemada, M. and Cabrera, M. L. (1997) Temperature and moisture effects on C and N mineralization from surface applied clover residue. Plant Soil. 189: Ram, N. (1998) Effect of continuous fertilizer use on soil fertility and productivity of a Mollisol. In: Swarup, A., D. D. Reddy, R. N. Prasad (Eds.), Long-term Soil Fertility Management through Integrated Plant Nutrient Supply. Indian Institute of Soil Science, Bhopal, India, pp Sahoo, D., Rout, K. K. and Mishra, V. (1998) Effect of twenty-five years of fertilizer application on productivity of ricerice system. In: Swarup, A., D. D. Reddy, R. N. Prasad (Eds.), Long-term Soil Fertility Management through Integrated Plant Nutrient Supply. Indian Institute of Soil Science, Bhopal, India. pp Saleque, M. A., Abedin, M. J., Bhuiyan, N. I., Zaman, S. K. and Panaullah, G. M. (2004) Long-term effects of inorganic and organic fertilizer sources on yield and nutrient accumulation of lowland rice. Field Crops Res. 86: Sims, J. T. and Wolf, D. C. (1994) Poultry waste management: Agricultural and environmental issues. Adv. Agron. 52: Singh, B., Singh, Y., Maskina, M. S. and Meelu, O. P. (1987) Poultry manure as an N source of wetland rice. Int. Rice Res. Newsletter. 12: Singh, P. and Gangwar, B. (2000) Nitrogen substitution through FYM in maize-wheat cropping sequence under irrigated conditions. In Proc. of International Conference on Managing Natural Resources for Sustainable Agricultural Production in the 21 st Century, New Delhi, India. 3: Solaiman, A. R. M. and Rabbani, M. G. (2006) Effects of N P K S and cow dung on growth and yield of tomato. Bull. Inst. Trop. Agr. Kyushu Univ. 29: Yoshida, S., Forno, D. A., Cock, J. H. and Gomez, K. A. (1976) Laboratory Manual for Physiological Studies of Rice. 3 rd ed. International Rice Research Institute, Manila, Philippines. Zang, W., Han, D. Y., Dick, W. A., Davis, K. R. and Hoitink, H. A. J. (1998) Compost and compost water extract induced systemic acquired resistance in cucumber and Arabidopsis. Phytopathology. 88:

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