The water irrigation in greenhouses, in the great majority, is linked to the empirical experience of the farmer. In this way situations of excess or deficiency could happen, to prevent whom is important the monitoring of the system with continuity and the immediate intervention as soon as it is needed.
A careful irrigation needs the utilisation of instruments detecting the humidity or the water potential at root level connected to an efficient distribution system. The utilisation of such instruments (e.g. tensiometers, TDR, FDR) is sometimes to heavy for a small farming business. A specific tool to assist the farmers in order to advice when and how to irrigate is furnished by the local supporting services of decision-making, which actually are offered free or on charge in many European localities. In Latium region is active the regional interactive free service IRRILAZIO. This, thanks to the data inputted by the farmer concerning soil’s, crops’, irrigation system’s properties, sends automatically an SMS message when the most favourable moment to irrigate is coming.

As concerning water distribution systems, it is preferable to utilise those at micro system, enabling to operate with small specific discharge (2-7 litres/h-1), soaking only the area of root interest. This kind of systems prevent erosion events, soil compacting, water flowing and even contacts between water and crops aerial parts. They are fully automatic settable and allow:
1) reduced leaching of the nutrients;
2) efficient distribution of fertilisers (fertigation);
3) reduced growth of unwanted weeds among the rows;
4) efficient operation on mulched soil;
5) labour save.

As concerning nitrogen distribution systems, these are in connected to the monitoring of the nutrition state of the crops thanks to optical diagnostic instruments. The researchers agree on the fact that a continuous monitoring of nutritional exigencies, in particular of nitrogen, allows a more punctual fertilizing management. This is based on a reduced input of fertilizer during the plantation phase, followed by fractioned inputs during the growth tailored on the effective necessities of the crops. Such operating method requests the availability of reliable diagnostic instruments. Some of these are already established among the farmers, especially in North America and North Europe, others are still in experimentation phase. They enable to do detect nitrogen concentration in leaves stalks or in the ending part of the stems (or to estimate on the basis of the optical characteristics of the plants the chlorophyll and total nitrogen content of single leaves). Whit different degree of precision and speed of measure, they allow the farmer’s immediate fertilizing intervention, when occurred. The more suitable technique to a fractioned and rational distribution of fertilizers is fertigation (the nutrients dissolved in water are distributed combined with the irrigation), this allows:
1) frequent small distributions of fertilisers, reducing the risk of leak of the nutrients;
2) reduced input of nutrients, especially when connected to monitoring instruments,
3) humidity level in the root area always high, avoiding too much concentration of the flowing solutions;
4) labour save.
Those techniques assume relevant importance in mulched soils, when fertilizers should otherwise be distributed totally before the crop plantation.

The results highlighted that, thanks to fertigation assisted by optical diagnostic instruments, inputs of nitrogen are considerably reduced in tomato for industry. In fact with this technique nitrogen distributed quantity was only from 30% to 60% respect to the fertilized crop with conventional granulate fertilizers, without damaging productions and obtaining greater fruits. The efficiency of the nitrogen fertilizing was considerably improved thanks to the adoption of these techniques.