cause of concern. In most of the farmers’ fields, particularly in sugarcane fields, efficient irrigation management practices such as irrigation scheduling, based on soil moisture status is rarely in practice. In an effort to save water and to facilitate irrigation scheduling, ICAR-SBI has developed this gadget a handy and user friendly electronic moisture indicating device, named “Soil Moisture Indicator”. This device was developed with the active participation of farmers and sugar factory personnel across three agro-climatic zones of Tamil Nadu through the Farmers’ Participatory Action Research Project (FPARP) during 2008-10. This device was tested by the farmers’ in their fields, comparing with the already known irrigation scheduling device ‘tensiometer’. From farmers experience, it was found that tensiometer has many inherent problems like permanent installation of multiple units in different places of the field, blocking of ceramic cup, regular filling of water in the reservoir tube immediately after irrigation, vacuum leakage problems, chances for breaking the ceramic cup of the field installed tensiometer, expensive (each unit costing about Rs. 4000/-). Soil moisture indicator was found better than tensiometer in assessing the moisture status of their fields and helped them to decide when to irrigate. Based on the farmers’ experience, it was found that scheduling irrigations based on soil moisture status considerably reduced the number of irrigations required for cultivating crops, thereby saving precious water without affecting productivity.


About soil moisture indicator About soil water, the field capacity and the permanent wilting point are two levels of moisture that are used to calculate available water for plant. This soil moisture indicator has been designed to objectively indicate soil moisture status. This device works based on the principle that electrical conductivity of the soil is directly proportional to soil moisture or soil electrical resistance is indirectly proportional to soil moisture content (similar to gypsum block technique). SMI has two metal sensor rods, when inserted in soil and on pressing the switch, the electronic circuit translates conductivity or resistance and indicates soil moisture level through a colour glow of LED. Three LEDs are provided for approximation and to suit different soils. The device indication is as follows, Moisture status slightly above permanent wilting point is indicated by red or orange LED light glow. This status indicate immediate requirement for irrigation. Soil moisture status sufficiently above wilting point and less than field capacity (sufficient soil moisture) is indicated by Green glow. No need for immediate irrigation can wait for few more days. Soil moisture at field capacity is indicated by Blue glow. Excess or more than sufficient soil moisture.

Problems associated with SMI

  • Measuring soil moisture is tricky and difficult, as it is very complex. The standard method is gravimetric oven drying method, which is practically not possible under field situations / farmers fields. Other highly sophisticated devices viz., neutron moisture probe, Ultrasonic Doppler systems etc., but these are very expensive and suitable only for research purposes; these are unsuitable for farmers use.
  • Soil moisture indicator will not give / measure exact soil moisture. This can only be used for objective indication of soil moisture and not for quantitative measurement.
  • This device measures soil electrical conductivity and translates to moisture indication. It is possible to get varied results / errors depending on different situations / conditions viz., heavy clayey or sandy soil, salinity, high soil and irrigation water EC etc. In all these problem situations, it is always possible to fine tune the electronic assembly appropriately before using/implanting the soil moisture indicator.

Advantages of using Soil Moisture Indicator Based on the farmers’ experiences, it was found that scheduling irrigations based on soil moisture status require 36 irrigations per sugarcane crop (12 months) compared to conventional farmers practice which require about 42 irrigations. This reduction in the number of irrigations did not affect the cane yield while saving precious irrigation water. But, one irrigation was quantified about 5 lakh litres per hectare, totalling about 30 lakh water is saved per hectare. The feedback from the cane growers of this device has been encouraging. This user-friendly device can be included in the government schemes for sensitizing the farmers about efficient use of irrigation water and scheduling irrigations based on soil moisture status. Cane yield and water savings in sugarcane under farmers’ holdings in three districts of Tamil Nadu


Sl. No. Item Conventional Irrigation Irrigation based on SMI
1 Cane yield (t/acre/crop) 55.8 60.4
2 Water usage 24600 m3 21000 m3

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