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Long Term and Permanent Manurial Experiments Permanent Manurial Experiments (PME) provide valuable information on the impact of long term adoption of nutrient management systems with varying sources, types and combinations of plant nutrient inputs on soil fertility and productivity. Such knowledge on resource base are vital for any decision support system which aim to demonstrate the role of society in sustaining agriculture and conversely, the role of soil in sustaining society. The world's oldest long term agricultural field experiments were begun between 1843 and 1856 by Lawes and Gilbert at Rothamsted in England. Eight of these experiments still continue. All were started as agronomic experiments to determine the nutrient requirements of agricultural crops. Although the original questions have long since been answered, they continue to provide data of considerable agronomic, ecological, environmental and scientific value. In the beginning of 20th century, based on Rothamsted model, in India also a series of long term fertilizer experiments were established at different locations in the country. These were at Kanpur, Uttar Pradesh (1905); Pusa, Bihar (1908); and at Coimbatore, Tamil Nadu (1909). Later on more long term fertilizer experiments were established on more heavily fertilized crop such as sugarcane at Shahijahanpur, (Uttar Pradesh) 1935; Padegaon, (Maharashtra) 1939; Indore, (Madhya Pradesh) 1947; Muzaffarnagar, (Uttar Pradesh)1949; and at Anaka Palle, (Andhra Pradesh) 1950 and on cereal based cropping system at Ranchi (Bihar) 1956. Unfortunately, some of these experiments were either discontinued or seriously altered as they were found inadequate in respect of the statistical requirement pertaining to the design of experiments or suffered from some management problems. However, the trials at Coimbatore and Ranchi are still being continued. With the advent of green-revolution, which triggered all types of resource management to meet the requirements of high yielding and potentially responsive crop varieties, a need arose to provide the data base information on changes in soil fertility under intensive farming for the decision support system on agricultural policy. This called for long-term sustained studies at fixed sites for monitoring the changes in the nutrient dynamics and with the objectives of developing strategies for intervention. The Indian Council of Agricultural Research (ICAR), therefore, in collaboration with State Agricultural Universities (SAU) initiated the All India Co-ordinated Research Project on Long Term Fertilizer Experiments (LTFE) in 1972 in 11 centres located in major agro-climatic zones of the country including TNAU, Coimbatore. Six of these ere located at Barrackpore, Bhubaneswar, Coimbatore, Delhi, Hyderabad and Ludhiana on inceptisols. some of these were on rice-based systems and others on maize, wheat or finger millet based systems. Three experiment were established on Alfisols at Palampur, Ranchi and Bangalore ; one each on Vertisols at Jabalpur and on Mollisol, at Pantnagar. Six more centers one each at Akola, Junagadh, Parbhani, Pattambi, Raipur and Udaipur were initiated during 1995-96 to represent additional agro climatic regions. The project is under the Natural Resource Management Division of ICAR and has 15 centers in different SAUs, two centers in ICAR Institutes with Coordination cell at Indian Institute of soil Science, Bhopal. The project at Coimbatore is functioning with one Associate Professor/ Sr. scientist, two Assistant Professors/ scientists, and one supporting staff. Long Term and Permanent Manurial Experiments in Tamil NaduIn Tamil Nadu Eleven Permanent Manurial Experiments are being conducted in various locations. These experiments represent different soil conditions and cropping systems and are most valuable because the data generated from them provide the basis for drawing conclusions on soil sustainability under continuous maintenance with different nutrient input systems both under rainfed and irrigated conditions. The Old Permanent Manurial Experiment started in a red soil, on the lines of Rothamsted Manurial Experiment has been in progress at this Institute since 1909. It is a non-replicated trial with ten different nutrient input systems (N, P, K, NP, PK, NK, NPK, Cattle Manure, and Cattle Manure Residue), irrigated upto 1937 and later maintained under rainfed conditions. So far 140 crops have been raised and the results have shown that higher yields could be obtained by the combined application of NPK. The cattle manure treated plots maintained the soil fertility status on par with NPK application. The organic carbon content increased upto 30 cm depth and decreased thereafter. The NPK experiment was started in two series called eastern and western series with the same set of treatments. Since the fertility status of the western series was initially low, to build up soil fertility, 2 t ha-1 of cattle manure is being applied basally, before taking up each experimental crop. In 1925, a New Permanent Manurial Experiment was started with the same set of treatments but under irrigated conditions. The results of 126 crops have shown that the treatments NPK, NP and cattle manure applications were on par and recorded higher yield over other treatments. The organic carbon content showed a general increase wherever cattle manure was applied. Phosphorus becomes a limiting nutrient when it is not applied. The yield reduction is to an extent of 50-60% continuous with holding of P from manuring schedule depleted native soil P to very low level of 3-4 kg ha-1, as against 10 kg ha-1 in P treated plots. Available K was depleted in control, N and NP plots (460 kg ha-1), as compared to NK, NPK and PK (980 kg ha-1) treatments. There was no alteration in the pH of the soil for continuous inorganic fertiliser application. Physical properties like water holding capacity, pore space and volume expansion of soil were all improved for continued NPK application as well as cattle manure application. The All India Co-ordinated Project on Long Term Fertilizer Experiments is in progress at this Institute since 1972. There are 10 treatments in this experiment. They are: T1 50% optimal NPK dose; T2 100% optimal NPK dose; T3 150% optimal NPK dose; T4 100% optimal NPK dose + hand weeding; T5 100% optimal NPK dose + Zinc or lime; T6 100% optimal NP; T7 100% optimal N; T8 100% optimal NPK + FYM ; T9 100% optimal NPK (Sulphur free/ sulphur source); T10 Unmanured (Control).
SALIENT ACHIEVEMENTS Crop responses to fertilizer NPK Continuous application of nitrogenous fertilizers alone adversely effected the soil productivity resulting in drastic reduction in yield to an extent of 75 - 80% in fingermillet, maize and cowpea due to phosphorus becoming the limiting nutrient. There was a spectacular improvement in crop yields when N and P were applied together as compared to N alone. The increase in crop yields due to the integrated use of N and P varied from 40 to 80 per cent. The soils being higher in available K status, combined application of N, P and K did not improve crop yields to any significant extent over that of N and P indicating non responsiveness to the application of K. Integrated use of FYM with 100 % NPK had significantly increased the yield of all the three crops in the sequence. Application of 100% NPK with 10 t/ha of FYM always produced the highest grain yield of fingermillet, maize and cowpea crops. The increase in yield over control and 100% N treatment was to the extent of about 200 per cent and 5 to 20 per cent over optimum NPK level. Build up and depletion of nutrients The soil N reserve as reflected by total N measurements was found to build up over years with all the nutrient input systems excepting no manuring and sub-optimal level of fertilizer NPK whereas, N availability in soil was maintained without appreciable change over years with all the nutrient input systems. Soil P reserve as reflected in total P measurements was found to increase over years in situations where P fertilization is done to optimal level, but in situations where fertilizer P is not applied, or applied at sub optimal level, the P reserve was found to decline. But, the P availability in soil was found to decline over years with all the nutrient input systems excepting high level of P application and combined use of FYM + fertilizer NPK. Soil K reserve was found to decline slowly, with intensive cropping irrespective of nutrient input systems followed. Similar is the case with K availability in soil also. There is also evidence that the crops started drawing on the non exchangeable source of K when the exchangeable K fell below the critical limits. Thus, for a rational policy for use of K fertilizer it is necessary to measure both exchangeable and non exchangeable sources of K in the soil. FUTURE THRUSTSEstablishing a National Network of Long Term Fertilizer Experiments (LTFE-NET) on lines with SOMNET of IACR- Rothemsted to enable easy and quick exchange of informations and to effect improvements based on such experiences. Developing norms / proposing protocols for the conduct of long term fertilizer experiments and generating data from experiment of such long term nature. Such an approach will enable development of suitable computer software packages common to all the centres. |
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