INTERNATIONAL JOURNAL OF ENVIRONMENTAL SCIENCES Volume 5, No 5, Copyright by the authors - Licensee IPA- Under Creative Commons license 3.

Transcription

1 INTERNATIONAL JOURNAL OF ENVIRONMENTAL SCIENCES Volume 5, No 5, 2015 Copyright by the authors - Licensee IPA- Under Creative Commons license 3.0 Research article ISSN Direct and residual effect of organic manures, urea integration on okra grown in sandy regosol Department of Agricultural Chemistry, Faculty of Agriculture, Eastern University, Sri Lanka, Sri Lanka. dhsharsha08@gmail.com doi: /ijes ABSTRACT In modern agriculture over use of inorganic fertilizers causes dangerous effects on environment, human health and loss of soil fertility especially in sandy regosols, where the poor soil structure promotes heavy leaching of nutrients. A pot experiment was carried out at Eastern University, Sri Lanka during the period of March to July 2014, to evaluate the residual soil nitrogen and nitrogen uptake of okra (Abelmoschus esculentus (L.) Moench) in sandy regosol using variety EUOK - 2. There were thirteen treatments replicated four times in Completely Randomized Design. They include poultry manure, farmyard manure, Leucaena (Ipil ipil) leaves and paddy straw as organic nitrogen sources and urea as the inorganic nitrogen source. The organic nitrogen sources were evaluated solely and in combination with urea at the rate of 50% and 100% from each in weight basis. These all treatments were tested with control with no organic nitrogen or inorganic nitrogen sources and were evaluated among themselves also. Among these treatments, significantly highest nitrogen uptake was registered in sole poultry manure application, highest Residual Soil Nitrogen (RSN) was recorded in 100% paddy straw integrated with 100% urea and the highest available soil nitrogen at the time of planting was in 100% poultry manure integrated with 100% urea. So sole poultry manure can be suggested to the farmers especially for the cultivation of okra on sandy regosol in order to maximize the nitrogen uptake and indirectly induce the growth performance and to reduce use of chemical fertilizers. Keywords: Farmyard manure, Leucaena leaves, okra, paddy straw, poultry manure. 1. Introduction Today fertilizer has become essential to modern agriculture to feed the growing population. Use of fertilizers, especially, the chemical fertilizers has brought in blessings on humanity, which helped contain hunger and death in different corners of the world. Though chemical fertilizers increase crop production; their overuse has hardened the soil, decreased fertility, strengthened pesticides, polluted air and water, and released greenhouse gases, thereby bringing hazards to human health and environment as well. Accordingly, scientists and researchers are seen arguing in favour of organic fertilizers as the best solution to increase nitrogen uptake, nutrient retention and to avoid soil pollution, many other threats to environment and life caused by overuse of chemical fertilizers. Sri Lanka mainly depends on agriculture for their economic growth. Therefore agricultural production of Sri Lanka should be increased according to the growing population where the cultivating land extent also has being a limitation. The predominant soil group in the coastal belt of Sri Lanka is sandy regosol (Quartzipsamments) which contain 95-98% sand with no Received on January 2015 Published on March

2 confining horizons in its soil profile (Bawatharani et al., 2004). As sandy regosols have poor nutrient supplying and water retention capacity (Ishida et al., 1993) farmers have to rely heavily on the use of external inputs on a seasonal basis. Among the major elements provided by chemical fertilizers, nitrogen is the most limiting element in the crop production. Nitrogen is highly vulnerable to losses. Little of the applied nitrogen is carried over to subsequent growing seasons due to crop removal, leaching, ammonia volatilization and denitrification. Of all the elements required for crop production, nitrogen poses the greatest environmental threat through contamination of surface and ground water (Tucker, 1999). Nitrogen loss and threat of ground water contamination increases under excessive inorganic fertilizer application on sandy regosols (EPA, 2005) and also the use of inorganic fertilizer has not been helpful under intensive agriculture because it is often associated with reduced crop yield, soil acidity and nutrients imbalance (Ojeniyi, 2000). The naturally available organic amendments are an important source of nitrogen used in low input agricultural systems and addition of organic amendments to soils improves soil properties and it is highly accepted by the farmers (Prapagar et al., 2012). Combinations of organic-mineral nitrogen sources have increasingly received recognition as integral and indispensable components of sustainable soil fertility management and significant advances also have been made on their influence on the soil chemical and physical properties (Palm and Rowland, 1997). Integrated plant nutrient management (IPNM) will increase the nutrient content of soil with good physical and microbial property. And thus will increase the availability of nutrients and cation retention which will directly increase the uptake of nutrients. Much information is available about the use of organic matter for okra; however, main emphasis here is to determine the impact of organic nitrogen sources and their integrations with inorganic nitrogen source on the nitrogen uptake of local okra cultivar (EUOK-2) and residual soil nitrogen. Therefore this pot experiment was conducted to study the effect of different organic nitrogen sources and their integration with inorganic nitrogen source on nitrogen uptake of Okra and the residual nitrogen in soil. 2. Material and methods 2.1 Description of the Experiment Site A pot culture experiment was conducted at Eastern University, Sri Lanka which is located in the latitude of N and the longitude of The experiment was carried out during the period of 10 th of March to 15 th of July, Soil Sampling and Preparation A bulk soil sample was collected at 0-20 cm depth from an area where cultivation was not previously carried out and it was processed and air dried for a day. The air dried soil was sieved (2mm mesh sieve). 2.3 Experimental Design and Treatments The organic nitrogen sources were evaluated solely and in combination with the inorganic nitrogen source, urea at the rate of 50% and 100% from each in weight basis. In sole organic manure treatments poultry manure, farmyard manure, Leucaena green leaves and paddy straw 981

3 were used at the rate of 10 tons/ha and urea was applied according to the fertilizer recommendation of Department of Agriculture, Sri Lanka as 300 Kg/ha. Other major nutrients P2O5 and K2O were applied at the rate of 200 kg/ha and 150 Kg/ha by Triple Super Phosphate and Muriate of Potash respectively. All the treatments were evaluated in comparison with the control. The 13 treatments including control were replicated four times in a Completely Randomized Design (CRD) and the treatments were, T1 T2 T3 T4 T5 T6 T7 T8 T9 T10 T11 T12 T13 Control (No fertilizer) Poultry manure Farmyard manure Leucaena leucocephala leaves Paddy straw 50% poultry manure + 50% urea 50% farmyard manure + 50% urea 50% Leucaena leaves + 50% urea 50% paddy straw + 50% urea 100% poultry manure + 100% urea 100% farmyard manure + 100% urea 100% Leucaena leaves + 100% urea 100% paddy straw + 100% urea 2.4 Pot Culture Experiment Black polyethylene bags were used for this experiment and were filled with 14 Kg processed soil. The organic and inorganic manures were incorporated according to the treatments and arranged conforming to the design. One plant per bag was maintained. All the agronomic practices were applied according to the recommendation of Department of Agriculture, Sri Lanka. 2.5 Measurements 1. Manure Analysis The total nitrogen content of poultry manure, farmyard manure, Leucaena leucocephala and paddy straw are 3.12%, 0.76%, 3.04% and 0.61% respectively. 2. Soil Analysis Soil analyses were carried out initially and at the end of the study for its available nitrogen content. The available nitrogen in each soil was determined by Micro kjeldhal method. 3. Plant Analysis Total nitrogen in plant parts were determined by Micro kjeldhal method. 2.6 Analysis of results Data collected were subjected to analysis of variance (ANOVA) using SAS 9.1 version statistical software package and mean comparison was performed within treatments using Tukey test at 5% significant level. 982

4 3. Result and Discussion 3.1 Soil Available Nitrogen at the Time of Planting There was significant influence of nitrogen sources on the nitrogen content of soil that is available for the crop use, as p value is less than IPNM application in the rate of 100% organic manures with 100% urea registered the highest nitrogen content of soil at the time of planting. Though the release of nitrogen from organic manures are slower than from inorganic sources but when both are combined, the immediate nitrogen requirement can be supplemented by inorganic nitrogen and the slow releasing nitrogen will be then sustain the needs of crop at later stages. The availability of NPK was increased in treatments combining organic manures with chemical fertilizers (Reddy and Reddy, 1998). Table 1: Effect of Nitrogen Sources on Available Nitrogen in Soil (Kgha -1 ) at the Time of Planting. Treatments Mean Soil Available Nitrogen at the time of planting (Kgha -1 ) T ± 2.11 j T ± 5.56 ed T ± 0.87 h T ± 6.09 f T ± 14.4 i T ± 9.50 f T ± 9.47 f T ± 0.57 e T ± 6.25 g T ± 4.40 a T ± 5.70 c T ± 9.25 b T ± 4.30 d F test * The value represents mean ± standard error of replicates * represents significant at 5% level of probability Mean values in the columns having same letter(s) within treatment group are not significantly different at 5% level of significance by Tukey Test. Among the treatments, nitrogen content of soil is significantly high in soil treated with 100% poultry manure + 100% urea (p < 0.05). This may be due to the immediate availability of nitrogen from chemical fertilizer portion and quick decomposition of poultry manure due to prominent ph increment, and thus makes better availability of nitrogen in it. C: N ratio of 9:1 in fresh poultry manure support the mineralization rate of 56% where the organic nitrogen is converted in to ammonium nitrogen which boost the available nitrogen content of the soil (Amanullah et al., 2010). 983

5 According to the results (Table 2) the second highest amount of soil available nitrogen was observed in the soil treated with 100% Leucaena green leaves with 100% urea. Incorporation of Leucaena increases the soil nitrogen content where legume green manures significantly increase the soil nitrogen when compared to the other green manures (Sangakkara et al., 2008). Available nitrogen was least in soil amended with paddy straw but was higher than the control. Utilization of nitrogen by microorganisms to decompose the organic matter could be considered as the causal factor, especially with rice straw, which has a higher C: N ratio (63:1) (Hirose, 1973). 3.2Nitrogen Uptake of Okra (Abelmoschus esculentus (L.) Moench). Experiment results revealed that there was significant influence of nitrogen sources on nitrogen uptake of okra as p value is less than Sole application of poultry manure gave the highest nitrogen uptake (76.62 gkg -1 ) while the control gave the lowest (10.37 gkg -1 ). Table 2: Effect of Nitrogen Sources on Nitrogen Uptake of okra (Abelmoschus esculentus (L.) Moench) Treatments Nitrogen Uptake (gkg -1 ) T ± 0.12 m T ± 0.37 a T ± 0.59 i T ± 0.12 c T ± 0.11 l T ± 0.50 e T ± 0.12 g T ± 0.22 f T ± 0.27 k T ± 0.22 b T ± 0.25 h T ± 0.34 d T ± 0.05 j F test * The value represents mean ± Standard Error of replicates * represents significant at 5% level of probability Mean values in the columns having same letter(s) within treatment group are not significantly different at 5% level of significance by Tukey Test. Among all the treatments sole paddy straw and its integration of 50% and 100% urea showed significantly low uptake than other treatments. The decomposition of sole paddy straw is slow, because of its high lignin, cellulose and low protein content. And also the results indicated that the straw has the potential to slowdown the microbial activity which convert the organic nitrogen in to inorganic nitrogen, even though additional nitrogen is added along with them, thus reduces the nitrogen uptake of the crop (Oladipo et al., 2010). Among all treatments control registered the lowest nitrogen uptake where the soil received neither organic manure nor urea. This may be due to unavailability of nutrients which might reduce the nitrogen uptake of okra. 984

6 4. Residual soil Nitrogen (RSN) Significant differences were detected between the control and other treatments at p < 0.05 and the residual soil nitrogen was significantly higher in treatment received 100% paddy straw and 100% urea. Table 3: Effect of Nitrogen Sources on Residual Soil Nitrogen (RSN) (Kgha -1 ) Treatments Mean Residual Soil Nitrogen (RSN) (Kgha -1 ) T ± 2.80 h T ± 6.15 f T ± 5.95 ef T ± 8.20 g T ± 2.80 b T ± 2.80 e T ± 1.05 e T ± 2.95 e T ± 1.95 d T ± 5.60 c T ± 15.2 d T ± 2.80 c T ± 16.8 a F test * The value represents mean ± standard error of replicates *represents significant at 5% level of probability Mean values in the columns having same letter(s) within treatment group are not significantly different at 5% level of significance by Tukey Test. As paddy straw is a highly carbonaceous material, immobilization was higher than treatments received other organic manures and nitrogen availability also low at the time of planting (Table 2). Large amount of nitrogen present in paddy straw but often leads to temporary nitrogen immobilization in the soil with adverse effect on early crop growth (Amarasiri and Wickramasinghe, 1978). But the residual soil nitrogen in the soil amended with paddy straw with 100% urea was higher than other treatments and it was followed by sole paddy straw application. The mineralization and release of temporarily immobilized nitrogen and the low uptake of nitrogen in paddy straw treated with 100% urea might increase the residual nitrogen in the post-harvest soil. It also may be due to the effect of chemical fertilizer which increase the decomposition rate of the organic fertilizers used (Pan et al., 2009) and nitrogen availability increases in soil when organic nitrogen sources combined with inorganic nitrogen sources but the nitrogen release was slow compared to the other organic manures, so the highest residual available nitrogen was recorded in this treatment. In sole paddy straw application, residual soil nitrogen was higher. Sole paddy straw application showed the lowest nitrogen uptake (Table 3.) among the treatments, and the slow 985

7 release of nitrogen (Cho and Ponnamperuma, 1971) consequently increase the residual soil nitrogen content (RSN). It was observed that the 100% organic nitrogen sources integrated with 100% urea recorded higher residual soil nitrogen (RSN). Additions of straw or manures along with inorganic fertilizers increase the residual effects of nutrients and increase crop productivity for long-term (Liu et al., 2013). Sole paddy straw was followed by 100% poultry manure integrated with 100% urea. It was stated that the relative efficacy of organic manures with respect to residual effect in all soils was higher in poultry manure (Gupta et al., 1988) except the relative efficacy of paddy straw applications. Soil received sole poultry manure registered the lowest residual soil nitrogen (RSN) as it registered the highest nitrogen uptake (Table 3) and it was on par with sole farmyard manure. The least residual soil nitrogen (RSN) was registered in control, as it received neither organic manures nor urea. 5. Conclusion The present study was conducted to investigate the possibilities in reducing the over usage of chemical fertilizers and increase the utilization of locally available organic manures. From the above study following conclusions were derived: Significantly highest soil available nitrogen at the time of planting was in 100% poultry manure integrated with 100% urea, significantly highest nitrogen uptake of okra was in sole poultry manure application and the highest residual soil nitrogen was in 100% paddy straw with 100% urea. 6. References 1. Amanullah, M. M., Sekar, S. and Muthukrishnan, P. (2010). Prospects and potential of poultry manure, Asian Journal of Plant Sciences, 9 (4), p Amarasiri, S. and Wickramasinghe, K. (1978). Use of rice straw as a fertilizer material, Central Agricultural Research Institute, Gannoruwa, Peradeniya. 3. Bawatharani, T., Mowjood, M. I. M., Dayawansa, N. D. K. and Kumaragamage, D. (2004). Nitrate leaching as a function of fertilization and irrigation practices in Sandy regosols, Tropical Agricultural research, 16, pp Cho, D. Y. and Ponnamperuma, F. N. (1971). Influence of soil temperature on the chemical kinetics of flooded soils and the growth of rice, Soil Science, 112, pp EPA, (2005). Protecting Water Quality from Agricultural Runoff, U.S. Environmental Protection Agency, Washington, DC. 6. Gupta, A. P., Antil, R. S. and Narwal, R. P. (1988). Effect of farmyard manure on organic carbon, available N and P content of soil during different periods of wheat growth, Journal of the Indian Society of Soil Science, 36, pp Hirose, S. (1973). Mineralization of organic nitrogen of various plant residues in the soil under upland conditions, Journal of the science of soil and manure, Japan, 44, pp Ishida, H., Chairoj, P., Morakul, P., Vibulsukh, N., Boonyong, B., and Wongwiwachai, C. (1993). Techniques to improve productivity of the sandy upland soil in northeast 986

8 Thailand, Agricultural Development Research Center in Northeast Thailand, Khon Kaen, Thailand.1, p Liu, E., Yan, C., Mei, X., Zhang, Y. and Fan, T. (2013). Long-term effect of manure and fertilizer on soil organic carbon pools in dry land farming in northwest China, Plos one, 8(2), e Ojeniyi, S. O. (2000). Effect of goat manure on soil nutrient and okra yield in a rain forest area of Nigeria, Applied Tropical Agriculture, 5, pp Oladipo, O. G., Olayinka, A., Aladesanmi, O. T., Sanni, M., Famurewa, A. J. and Siyanbola, W. O. (2010). Risk mitigation strategies and policy implications for carbon dioxide emission in organically-amended soils, pp Palm, C. A. and Rowland, A.P. (1997). Chemical characterization of plant quality for decomposition. In: G. Cadisch, and K. E. Giller, (Eds.). Driven by Nature, Plant Litter Quality and Decomposition, CAB International, Wallingford, pp Pan, G., Zhou, P., Li, Z., Smith, P., Li, L., Qiu, D. and Chen, X. (2009). Combined inorganic/organic fertilization enhances N efficiency and increases rice productivity through organic carbon accumulation in a rice paddy from the Tai Lake region, China, Agriculture, ecosystems & environment, 131(3), pp Prapagar, K., Indraratne, S. P. and Premanandharajah, P. (2012). Effect of Soil Amendments on Reclamation of Saline-Sodic Soil, Tropical Agricultural Research, 23 (2), pp Reddy, G. B. and Reddy, M.S. (1998). Effect of organic manures and N levels on soil available nutrients in maize soya bean cropping systems, Journal of Indian Society of soil science, 46 (3), pp Sangakkara, R., Weerasekera, D. and Freyer, B. (2008). Green manuring for tropical organic cropping A comparative analysis, Poster at. Cultivating the Future Based on Science: 2nd Conference of the International Society of Organic Agriculture Research ISOFAR, Modena, Italy. 17. Tucker, M. R. (1999). Essential plant nutrients, their presence in North Carolina soils and role in plant nutrition. 18. Zoysa, A. K. N., Keerthisinghe, G., Jayakody, A. N. and Upasena, S. H. (1989). Ammonium Dynamics in a Leucaena Green Manure Incorporated Puddle Rice Soil, Department of Agriculture, Kirandurukotte. 987