13.1 introduction

Recent developments in weather and seasonal rainfall prediction have increased the accuracy and reliability of forecasts of the indian monsoon. Despita these advances, availability and access to location specific forecasts to take proper decisions at the farm level is very limited. Traditionally farmers in india have been using a set of indicators that have varied levels of dependability for rainfall prediction and have evolved sev-eral coping strategies and mechanisms.

The M. S. Swaminathan research foundation (MSSRF), Based at chennai, india initiated a project on “establishing decentralized climate forecasting system at the vil-lage level” to create and enhance farmer’s capacity to use locale-specific seasonal rainfall and weather forecasting in collaboration with reddyarchatram seed growers association (RSGA), a farmers association at kannivadi in dindigul district of tamil nadu state, india. The msin goal of the project is to create an access and enhance farmer’s capacity to use location specific seasonal climate and weather predictions to improve their livelihoods. The major objectives are to study the seasonal climate variations and chroniclet the farmer’s traditional coping strategies and knowledge.the study also aims at evolving a methodology for downscaling with appropriate institutional linkages and converting the generic data into location-specific, medium term, inter and intra-seosonal climate and weather forecasts. Probabilistic seasonal climate and weather forecats information is translated into appropriate farmer friendly versions for its practical use in crop management.

13.2 Study Area

Reddyarchatram block is a semi-arid region located in dindigul district of Tamil Nadu, India, covering a geographical area of 280 km2. More than 80% of the households in the district depend on agriculture. Important planting seasons are juny_july and october november for both the irrigated and rainfed crops, in addition to the summer irrigated crop. The mean annual rainfall is 845.6 mm. Raifall in the region is characterized by a large variation between seasons. Though the area benefits both from the northeast monsoon (october-december) and the southwest monsoon (june-setember), maximum percentage (52.5%) of rainfall is received during the northeast monsoon and nearly 25.8 % of the total annual rainfall is received during monsoon. The area receives only 5.4% of the total annual rainfall during january and february and nearly 16.3% during the summer seasons between march and may. The total area under cultivation is 24.624 ha which includes both dry and irrigated lands. Approximately 29.600 households are involved in agriculture and more than 50% of the households are small and marginal farmers. Sorghum, small millets, grain legumes, cotton and chickpea are the major annual crops cultivated under rainfed conditions. Cotton, Maize, flower crops, vegetables, gherkins, sugarcane, annual moringa, paddy, onion, etc. Are the most important annual crops grown in this region. The major source of irrigation is underground water through wells followed by small tanks and reservoirs.

13.3 Methodology

The study was initiated during October 2002 to March 2004in five villages where village knowledge Centers (VKCs) are functioning.The computer based village knowledge centers with internet connection provides static information about the agronomical practices of the different crops cultivated in the region and the dynamic information like price details of the main agrikultural produce from diffrent markeets,availability of inouts,farmers entitlements,etc.A setof VKCs are operating in yhe region connected with a ‘hub’in the center and the ‘hub’is the nodal point,which receives the generic information and adds value by converting it to local specific information.The local community manages the VKCs; access is ensured to all irrespec tive of caste,class,gander and age.Need based content creation is being regularly done on the basis of the feed back from the local women and men farmers.The local village people have been trained in the management of modern information and communication technologies including networking.

In each village,traditional knowledge system on weather and climate was stedied through convetional survey using questionnaire,anthropological tools such as participant observation,and participatory developmental tools such as Venn diagram and Focus Group Discussions (FGD).The traditonal weather and seasonal rainfall predictors were studied among the selected sample households through questinnaires.Anthropological tools such as open-ended interviews were used to study the metaphors,folklore and proverbs that gave a better perspective on the traditonal knowledge.A series of participatory Rural Appraisals (PRAs) werw organized in representative villages in the block that facused on the social system,existing natural resuerces,agricultural seasons and ralnfall patterns and also on the prevailing pattern and system of information flow.The needs,constraints and coping strategies on weather and climate of farmers and agricultural laborers were assessed through FGD and these views were triangulated through informal disscusion with knowledgeable men and women farmers.

MSSRF facilitated linkages to get the scientific forecast beween hub of the vksc and national centre for medium range weather forecast(NCMRWF)for medium range weather forecast and the tamil nadu agricultural university(TNAU)for seasonal rainfall forecast.the hub centre manages a’B’observatory;animators were trained in observatory management with thetechnical support of TNAU.they regulary record the localweather parameters(maximum and minimumtemperature,soil temperature at different depths,sunshine hours,wind direction and velocity,evaporation rate,relative humidity)according to the norms of indian meteorological department in the prescribed format and communicate the same to NCMRWF twice a week throughelectonic mail.in turn NCMRWR provide weather forecast twice a week to the hub center on cloud cover,precipitation,temperature,wind direction and wind velocity,similarly,linkages were established to receive the seasonal rainfall forecast from TNAU.

The hub center receives the forecast and converts the generic information received from these two institutions into locaction-specific farmer friendly language(for example if the wind direction is 100 0, it is communicated to the particular village in their local parlance) and disseminates the information to farmers and agricultural laborers through VKC,bulletin boards and local newspaper.

Initially MMSRF trained the animators to convert the generic information into farmer friendly versions.The information is being communicatet to other VKCs though fax mode and can be accesible though multimedia folders using internet.The messages are communicated to nearby villages by the VKCs though bulletin boards that are located in 15 differendt villages.A focus group discussion was carried out in each of the villages with the men and women to communicate the forecast.Initoally we explaind the method by which the scientific forecasts were generated and its attributes to the farmers.The probabilistic nature of the seasonal rain forecast was explained to the farmers,and simple locally familiar games were organized to clearly explain the concept of exceedance’ graph was generated to clearly explain the concept of probability.then using the climatological data analysis probability of exceedance’grap was generated to explain the relationship between rainfall amount(forecast) and probability.attempts are being made only to communicate the forecast information to the people instead of giving follow-up advisories.it allows the farmer to take decisions based on the event of rainfall and follow dynamic strategies instead of a single strategy as most of the forecasters recommend.the entire process is institutionalized through VKCs.

13.4

Result and discussion

Understanding people’s perceptions and knowledge of weather and climate is critical for effective communication of scientific forecasts.the knowledge is learned and identified by farmers with in a cultural context and the knowledge base follow a specific language,belief and process.the local men and women members assess,predict and interpret by locally observed variables and experiences using combinations of plants,animals,insects,and meteorological and astoronomical indicators. farmers use different kinds of traditional knowledge for rainfall prediction on their observation with differenttypes of phenomena like wind movement,lightening,animal behaviors,birds movement, halos/rings around the moon and the shape and position of the moon on 3rd to 5th day from the formation,etc.this type of knowledge provides a framework to explain the relationships between particular events in the climate and farming.farmers use different types of predictors (based on environmental and biological criteria)in combination to take critical farming decisions and to decide on adaptive measures. The knowledge is evolved by locally defined conditions and needs, in other words this knowledge is context specific.

Men and women have different kinds of knowledge and use it for different purposes. Similarly village elders are more knowledgeabel and are able to use more indicators with greather understanding of the reliability of various indicators. The older man and women where able to provide more than 12 indicators with different lead times, whereas the middle aged (25 to 35 years) persons could provide only 3-4 indicators. Farmers as well as agricultural laborers have their own indicators that are based on their need and interactions. Also, farmers are able to provide more indicators than the agricultural laborers. The variations in the indigenous knowledge in a comunity are based on age, gender, caste, class and literacy.

The indicators clearly show that this indigenous knowledge on seasonal rain vall and weather is qualitative in nature. Weather predictions are used to take short-term decisions both in the irrigated and rainfed systems. It helps the small and marginal farmers to plan various agronomic practices more effectifely especially at the time of sowing, weeding, spraing of chemicals and harvesting and post harvest operations. However, farmers use seasonal rainfall predictions to prepare themselves for anomalies related to rainfall for example it helps to decide the cropping pattern for that season, if the rainfall is normal, they can go for high value crops like maize with high yielding farieties, otherwise if it is below normal they can plan for short duration drought resistan pulses and small milliteds. Farmers have been using different strategies to adapt and cope up with ucertain weather and climate based on their experience and acquiret and knowledge from previous generation. The importan decisions are selection of cropping system, mobilizing seed, fertilizer and application, decisions on sowing (early or late), lan and bed the preparations, mid season corrections such as reducing population/providing irrigation. Similar to the seasonal forecast, weather forecast is being useful for the small and marginal farmers to plan the agronomic practices more effectively especially at the time of sowing, weeding, spraying of chemicalsa and harfesting and post harfest operations.

In the Focus Group Discussion farmers expressed that the increasing variability in rainfall have reduced the farmers’ confidence in their own predictors and hence they are increasinggly looking for scientific forecasts. They expressed they fariability and terms of more whater devicid years, late onsed of rains and premature end of rains, and irregular distribution in time and space. Climatological analysis of the inter annual variability using 20 years of annual rainfall in this region indicated that the variability was about 36% and across the seasons the variability in therm of CV is high during the southwest monsoon season (71.6 %) followed by the northeas monsoon season (52.2 %). Hence, the callenge and nessecity is to provide reliable forecasts through appropriate methods based on the needs of the farmers.

During 2003 and 2004 winters,moonson rainfall amount was predicted and com municated to the farmers.Based on the two years experience,farmers incated that it is very difficult to take decisions in the farm based on this forecast informaton.in stead,it might help them to prepare againts anomalies in the future,profided the fore casts are accurate over years.Though farmers are listening and carefully monitoring the correlations,they expressed that they need time to observe the effectiveness of scientific forecasts over seasons or years.Based on the request of the farmers,four rainfall measuring devices were installed in different villages in this region and the rainfall was carefully recorded by the knowledge centers.

Farmers expressed that their traditional practice follows dynamic strategies based on the event of rainfall,which is completely different from following a single strategy based on one predicition before the crop cultifation.They expressed that their existing strategies are more practical,evolved locally over years through trial and error considering the available natural resources.thus the forecasts of a single rainfall amount do not support taking any short-term (e.g.like crop variety or plant population per unit area ) or long-term decisions (like cropping system:monocropping or mixed cropping,etc.).Another important issue is that the probabilistic mode of the total amount of rainfall does not support farmers’need in terms of time of onset of rainfall and its distribution.it is one of the significant variables requested by the farmers to make decisons on initial agricultural activities,which may help to reduce the risk.Though farmers could understand the probabilistic nature of the rainfall over season,they expressed that it is very difficult to opertionalize it,since it is not providing confidence (moral support) to the farmers,instead it indicates the lack of certainty and based on this they could not take major decisions.also the two years experience indicates that learning takes time (observation over time\seasons) and the use has to do with familiarity.

With regard to the medium range weather forecasts,attempts are being made only to communicate the forecast to the people instead of giving follow-up advisories based on the forecasts. It allows the farmer to take decissions based on his/her field conditions.this is because under local situations,due to the heterogeneous nature of the field and crop conditions farmers take decisions based on the event and they have been following dynamic strategies instead of a single strategy which the forecasters recommend.A survey was organized to know the impact of the forecast information and nearly 66% of the farmers expressed that have used it for taking farm management decisions.Around 72% of the farmers expressed the need for receiving forecasts at a much longer lead time interval,mostly 10 to 15 days.

13.5

Preliminary conclusins

The study clearly brought out the importance of the vast traditional knowledge of the farmers on rainfall prediction and their understanding of its reliability through their observation, experience and practice in the field. The social stratification influences the evolution and managemant of knowledge. Understanding the local people’s perceptions on rain fall prediction is necessary to communicate the scientific forecasts, since it is learned and identified by farmers within a cultural context and the knowledge base follows the specific language, belief and process. Intensive participatory dialogue between the scientific knowledge providers and user group’s helps to define the strategies for using the forecasts in combination with traditional knowledge and skills. The project helped us to understand that, to develop a decentralized forecasting system at the village level needs a participatory approach to mobilize the farmers around the technology. On the other hand, acces, availability of infrastructure, skill and expertise are crucial to develop reliable region-specific scientific forecasts to serve the ferming societies. Farmers may not heavely rely on scientific forecasts until the forecasts have proven its reliability. At this phase due to the limited experience and observation it is difficult to derive any conclusion. It helps us to set the system and in the process slowly build up the farmer’s understanding and cofidence in scientific forecasts.

Ackonowledgements

The author would like to thank Dr James, IRI for Climate Prediction, New York, USA and Dr Roland Fuchs, Director, START Secretariat, Washington DC, USA for providing the opportunity to undergo training and subsequently to carry out the project. The financial support provided by the David and Lucile Packard foundation, USA is graterfully acknowledged. The author extends her sincere thanks to Dr. Sulochuna Gadgil, IIS, Bangalore for providing technical and moral support and fruitful mentorship for the projec. Author expresses deep gratitude for the technical support extended by TNAU, NCMRWF and Indian Institute of Tropical Meteorology (IITM) and the local farmer’s association for actively taking part in establishing a decentralized village level forecasting system. The author sincerely thank Prof. M. S. Swaminathan, Chairman and Dr. K. Balasubramanian, Program Director of M. S. Swaminathan Research Foundation for their encouragement and guidance on conceptualization and implementation of the initiative.

Tanah tersusun dari bahan padatan, air, dan udara. Bahan padatan tersebut dapat berupa: bahan mineral, dan bahan organik. Bahan mineral terdiri dari partikel pasir, debu dan liat. Ketiga partikel ini menyusun tekstur tanah. Bahan organik dari tanah mineral berkisar 5% dari bobot total tanah. Meskipun kandungan bahan organik tanah mineral sedikit (+5%) tetapi memegang peranan penting dalam menentukan Kesuburan Tanah.

Definisi Bahan Organik

Bahan organik adalah kumpulan beragam senyawa-senyawa organik kompleks yang sedang atau telah mengalami proses dekomposisi, baik berupa humus hasil humifikasi maupun senyawa-senyawa anorganik hasil mineralisasi dan termasuk juga mikrobia heterotrofik dan ototrofik yang terlibat dan berada didalamnya.

Sumber Bahan Organik Tanah

Sisa-sisa tanaman baik yang berupa daun-daun, ranting-ranting, batang, dan akar-akar tanaman baik yang masih segar maupun yang sudah terurai merupakan penyusun bahan organik tanah yang terbesar. Sebagian kecil tersusun atas makro dan mikrobia tanah yang sudah mati. Di dalam tanah bahan organik ini senantiasa mengalami penguraian sebagai akibat kegiatan mikroba tanah.

Perombakan mulai dari yang komplek menjadi senyawa yang lebih sederhana sampai akhirnya menjadi kation dan ion-ion yang dilepaskan ke dalam tanah. Lama-kelamaan bahan organik tanah akan habis sehingga perlu mendapatkan tambahan. Tambahan itu diperoleh dari:

a). Tanah-tanah hutan, daun-daun dari berbagai tanaman dan sisa hewan yang mati pada permukaan tanah.

b). Pada tanah pertanian bahan organik diperoleh dari sisa tanaman setelah panen, bebagai macam rumput liar, tanaman penutup tanah, dan berbagai pupuk hijau yang dimasukkan ke dalam tanah pada waktu pengolahan tanah.

c). Sumber lain dari bahan organik tanah adalah pupuk kandang, kompos dan berbagai jasad hidup yang sudah mati dalam tanah. Bahan organik yang sudah membusuk akan menjadi bahan humus yang sifatnya lebih stabil.

Humifikasi

Huminifikasi adalah proses pembentukan humus dalam pengolahan bahan organik tanah. Bila tata udara baik dan lancar serta kelembaban cukup maka organisme yang telah mati segera diserang oleh mikro dan makrobia tanah seperti bakteri, cendawan, Protozoa dan Nematoda. Yang mudah terurai adalah dari golongan karbohidrat, protein sedang lemak dan selulose agak lambat.

Lignin dan lilin karena mengandung minyak paling lambat penguraiannya. Dengan adanya penguraian ini lambat laun terjadi pengumpulan lignin dan sisa yang tahan penguraian. Kedua bahan ini bersama protein membentuk suatu senyawa baru tahan penguraian yang disebut humus.

Humus berwarna coklat atau coklat kehitam-hitaman, berbentuk non kristalin, dan bersifat koloidal dan mempunyai perbandingan karbon dan nitrogen umumnya antara 10 – 20 %. Di dalam tanah yang terpelihara baik-baik dan dimana aktivitas bakteri optimal, humus merupakan bagian terbesar dari bahan organik total, yakni 80 – 90 %.

Peranan bahan organik tanah

Bahan organik yang telah mengalami penguraian, akan terjadi humifikasidan mineralisasi. Pada humifikasi akan terbentuk humus yang relatif stabil, warna coklat kehitam-hitaman dan bersifat koloidal. Sedang pada mineralisasi dilepaskan berbagai senyawa dan unsur-unsur yang berperanan sebagai unsur hara tanaman. Di dalam tanah bahan organik dan humus bercampur dengan bagian-bagian mineral tanah, sehingga bahan organik memegang peranan:

1. Mempengaruhi sifat-sifat fisik tanah:

a.) Warna tanah menjadi coklat kehitam-hitaman.

b). Mempertinggi daya pengikatan air, mempengaruhi struktur tanah terutama pada tanah liat sehingga air dan udara menjadi lancar dan mempermudah pengolahan tanah. Pada tanah yang berpasir mempermudah terbentuk agregat-agregat tanah sekunder yang mudah mengikat air.

c). Warna tanah yang coklat kehitam-hitaman dapat lebih cepat menyerap panas matahari sehingga temperatur tanah bisa naik yang dapat merangsang perkembangan dan kegiatan tanah.

d). Dapat bekerja sebagai pengikat butir primer tanah sehingga dapat menaikkan kemantapan struktur tanah yang tidak mudah rusak karena air hujan.

2. Mempengaruhi sifat-sifat kimia dan kesuburan tanah

a). Menaikkan nilai tukar kation tanah.

b). Merupakan gudang unsur hara dengan melepaskan berbagai unsur pada mineralisasi dan humifikasi bahan organik.

c). Mempertahankan reaksi tanah dan pencucian dengan mengabsorpsi kation-kation dan anion-anion dalam tanah.

d). Asam organik dan asam anorganik yang dilepaskan pada penguraian bahan organik, membantu menguraikan mineral-mineral dan bahan induk tanah.

3. Mempengaruhi kehidupan jasad hidup tanah

Bahan organik merupakan sumber makanan dan energi bagi jasad hidup tanah pada waktu terjadinya penguraian senyawa-senyawa komplek diubah menjadi senyawa-senyawa sederhana dan unsur bebas. Tanpa adanya jasad hidup tanah unsur hara tanaman dalam bahan organik tetap dalam bentuk tidak tersedia bagi tanaman.

Mempertahankan Bahan Organik Tanah

Usaha untuk mempertahankan bahan organik tanah dan untuk menaikkan dengan jalan sebagai berikut:

1). Mengembalikan sisa-sisa bekas tanaman, terutama bahan organik yang mempunyai nilai perbandingan C : N rendah, jangan mengadakan pembakaran sisa-sisa tanaman.

2). Adakan pergiliran tanaman yang tepat.

3). Tanah dipupuk dengan berbagai pupuk hijau, atau tanaman penutup tanah.

4). Dapat juga tanah diberi pupuk kandang dan kompos.

5). Perlu adanya tanaman tumpang sari dan tanaman penutup tanah sehingga oksidasi bahan organik secara langsung dapat dihindari.

6). Dengan mengadakan pengolahan tanah yang cukup, dan mencegah adanya erosi di musim penghujan.

Tanah yang paling baik untuk tanaman adalah tanah yang subur, yang kaya akan sat hara yang dibutuhkan oleh tanaman. Selain subur juga tanaman membutuhkan air yang cukup dan kepadatan tanah yang memadai. Tanaman hortikultura sangat baik tumbuh pada tanah yang remah yaitu tanah yang tidak keras dan tidak berair banyak. Untuk meremahkan tanah agar rata, setelah dibajak kemudian dicangkul.

SUMBER

http://dasar2ilmutanah.blogspot.com/2007/11/bahan-organik-tanah.html/

http://pengertian-definisi.blogspot.com/2013/02/bahan-organik-tanah.html/

http://zonabawah.blogspot.com/2011/04/biologi-tanah-dan-bahan-organik-tanah.html/