**3. Soil moisture balance computation**

Computation of the soil water balance is an important aspect which needs to be focused, and their detailed methodological understanding is a must more particularly for the budding scientists. Nowadays, many research papers are published in the journals of repute, publishing effect of RCTs, namely, laser leveler, DSR, zero tillage, etc., on improving the water as well as land productivity without discussing much on the estimation part. Thus, there is confusion in between the scientists especially budding ones as to how to estimate the performance of a particular RCT under different conditions of soil texture and climate. Moreover, there is an interest in the evaluation of these RCTs in improving the production potentials by diverting maximum ET water to the T components, thereby providing higher nutrients to the plants [15, 25, 26] and recommending them as per the soil textural class as these technologies are location specific and not a single technology is capable of performing equally under all the conditions. Hence, there is a need to delineate the estimation/calculative part of the different moisture balance components of the soil.

Nowadays, agricultural scientists are focusing on techniques to reduce the soil evaporation [27–30] for partitioning higher part of the soil moisture from evaporation (unproductive component) to the transpiration (productive component) for improving the grain yields of the farmers of the water-stressed regions throughout the globe. Countries, namely, Switzerland, the USA, Germany, the Netherlands, Sweden, etc., recognized the significance of the aquifer management [29, 31]. Proper water allotment, as per demand and availability, is a decisive issue [29, 32]. Further, to feed 9.5 billion population up to 2050 [33], around 60% more food [34] is required to produce from the shrinking natural resources, namely, land and water [29, 35–37]. One other claimed way is to use waste or industrial water, but it needs efforts to clean it first which sometimes is not an easy step. Climate change further complicated the conditions as it has a significant effect on the agriculture by altering the rainfall patterns, CO2 concentration, air temperature, etc. [29, 36, 38]. Improved standards of living [39] and altered eating habits [8], which need more consumption of water, make the scenario more complex. Therefore, a challenge in front of the agricultural scientist to come out from this situation seems to be a bit difficult. The only way is to partition greater fraction of evapotranspiration (ET) component share to the transpiration side for improving the land productivity even in the water-stressed region, but without knowing the proper procedure for calculating the evaporation component, the budding scientists will not able to assess the impact of different RCTs for this partition. Therefore, estimation of the different soil moistures/water balance components is a must and of course very important for having an idea to what are the added water amounts (through rainfall or irrigation) and what are the lost amounts (either through evaporation, transpiration, seepage, drainage, change in profile moisture storage, etc.). Among all the water lost components on the left side, evapotranspiration generally denoted by ET is most important whose share remained almost the same [29, 38]. Further among ET, E pertains to unproductive water from open surfaces which must be partitioned to T for having higher yields [8, 20]. However, water loss through D and S is always away from the rhizosphere and thus is not used by the crop plants for meeting their ET requirements.

*Delineation of Soil Moisture Potentials and Moisture Balance Components DOI: http://dx.doi.org/10.5772/intechopen.92587*

Before sowing and after harvesting the crop, namely, during the intervening periods, profile moisture storage change could be measured, which further played an important role in the cultivation of fodder crops. A soil water balance component provides a way out to identify technologies which improve water productivity. Up to now, this period is the least attended as results of applied treatments evaluated are analyzed during this period [20, 27, 40, 41]. However, the intervening period delineation of soil moisture dynamics helped to assess the residual effects of these RCTs applied during the main crop [40, 41]. Therefore, for sustainable and judicious use of irrigation water, the analysis of the soil water balance component is very important. The following are the important parameters of the soil water balance which needs to be calculated for evaluating the performance of any RCT in any region of the globe:

$$\mathbf{E} + \mathbf{T} + \mathbf{D} + \mathbf{S} + \Delta \mathbf{G} = \mathbf{R} + \mathbf{I} \tag{5}$$

where E is the evaporation, T is the transpiration, D is the drainage, S is the seepage, ΔG is the profile moisture change, R is the rainfall, and I is the irrigation.

Details along with their calculative/instrumental part are discussed below.

#### **3.1 Rainfall (R)**

biomass [24]. Domestic activities such as bathing and dishwashing constitute the "gray water," while "black water" is the produce of laundry which consists of toilet water. Among all the different categories of water, only gray water has the huge potential of being reused, which further cut off the freshwater demand by 30% in cities [9].

Computation of the soil water balance is an important aspect which needs to be focused, and their detailed methodological understanding is a must more particularly for the budding scientists. Nowadays, many research papers are published in the journals of repute, publishing effect of RCTs, namely, laser leveler, DSR, zero tillage, etc., on improving the water as well as land productivity without discussing much on the estimation part. Thus, there is confusion in between the scientists especially budding ones as to how to estimate the performance of a particular RCT under different conditions of soil texture and climate. Moreover, there is an interest in the evaluation of these RCTs in improving the production potentials by diverting maximum ET water to the T components, thereby providing higher nutrients to the plants [15, 25, 26] and recommending them as per the soil textural class as these technologies are location specific and not a single technology is capable of

performing equally under all the conditions. Hence, there is a need to delineate the estimation/calculative part of the different moisture balance components of the soil. Nowadays, agricultural scientists are focusing on techniques to reduce the soil

evaporation [27–30] for partitioning higher part of the soil moisture from evaporation (unproductive component) to the transpiration (productive component) for improving the grain yields of the farmers of the water-stressed regions throughout the globe. Countries, namely, Switzerland, the USA, Germany, the Netherlands, Sweden, etc., recognized the significance of the aquifer management [29, 31]. Proper water allotment, as per demand and availability, is a decisive issue [29, 32]. Further, to feed 9.5 billion population up to 2050 [33], around 60% more food [34] is required to produce from the shrinking natural resources, namely, land and water [29, 35–37]. One other claimed way is to use waste or industrial water, but it needs efforts to clean it first which sometimes is not an easy step. Climate change further complicated the conditions as it has a significant effect on the agriculture by altering the rainfall patterns, CO2 concentration, air temperature, etc. [29, 36, 38]. Improved standards of living [39] and altered eating habits [8], which need more consumption of water, make the scenario more complex. Therefore, a challenge in front of the agricultural scientist to come out from this situation seems to be a bit difficult. The only way is to partition greater fraction of evapotranspiration (ET) component share to the transpiration side for improving the land productivity even in the water-stressed region, but without knowing the proper procedure for calculating the evaporation component, the budding scientists will not able to assess the impact of different RCTs for this partition. Therefore, estimation of the different soil moistures/water balance components is a must and of course very important for having an idea to what are the added water amounts (through rainfall or irrigation) and what are the lost amounts (either through evaporation, transpiration, seepage, drainage, change in profile moisture storage, etc.). Among all the water lost components on the left side, evapotranspiration generally denoted by ET is most important whose share remained almost the same [29, 38]. Further among ET, E pertains to unproductive water from open surfaces which must be partitioned to T for having higher yields [8, 20]. However, water loss through D and S is always away from the rhizosphere and thus is not used by the

**3. Soil moisture balance computation**

*Soil Moisture Importance*

crop plants for meeting their ET requirements.

**10**

Rainfall is an important soil water balance component which decides the fate of the rainfed crops grown particularly in the submountainous tracts where there is no irrigation facilities, which might be because of the hard subsurface and very deep underground water table [17, 23]. Therefore, its timely quantification is very important for recognizing stressed areas which further helps in rescheduling irrigation plans for improving land and water productivity over here. Received rainfall is estimated using a rain gauge, which is installed permanently at the location/period of experimentation, which is further used in calculating the rainfall water productivity (WPI) [15]. However, one should be very careful that the spot selected for rain gauge installation should be away from huge buildings or any obstacles or any hindrance. Necessary correction factor must be applied, which is the case of the heavy rainfall if rain gauge's cylinder overflowed [39]. Many times, it is observed that rain gauge base is not fixed, which may result in tilting of the gauge while recording the rainfall; thus while installing it, it should be made sure that it should be fixed by using cement and sand mixture, so that no error in calculations will be there [15, 23, 39].

#### **3.2 Irrigation water amount (I)**

Irrigation is the most important for having potential agricultural yields in any area. But generally irrigation water-use efficiency is quite low in spite of the fact that water already is a limiting factor. Further, irrigation is an important input component for soil water solution; however, its exact measurement is generally not there, even in water management experiments. Nowadays we are well equipped with the water measuring meters which accurately measured the water amount which is being applied to a particular plot under any treatment, namely, area velocity flow meter (AVFM 5) which provides a digital reading of water supplied in any plot [15]. Generally, irrigation water depth of 50 and 75 mm in wheat and rice plots supplied which could be measured through the sensor (fitted in the pipe through which water enters a particular plot) of AVFM [27]. GREYLINE is the company manufacturing the Digital flow meter (**Figure 8**) the irrigation water measuring irrigation water device on a quantitative basis. Their sensor has to be fit

The inner PVC tube weight was measured daily at 0.900 hours (**Figure 9d**) using a digital weighing balance. Mini-lysimeters are used (**Figure 9a**–**d**) in the treatment plots, where daily evaporation needs to be worked in mm below the crop canopy [20, 42, 43]. Providing permanent location in the field plots receiving differential treatments throughout the season is the main objective of providing outer PVC pipe, where evaporation could be regularly measured. Hammer is used for inserting the narrower inner PVC pipe in the field during each sampling (**Figure 9a**), which removed from the plot with the help of chain-pulley arrangement (**Figure 9b**). Weeds growing on the mini-lysimeters must be cut and removed, so that it may not affect evaporation readings. Without any soil disturbance, inner pipes should be placed in the outer pipes, and daily in the morning, about 9:00 am, lysimeters were weighed (**Figure 9d**) and placed back in

*Delineation of Soil Moisture Potentials and Moisture Balance Components*

Mostly, very little discussion is there in different research papers regarding the calculative part of the evaporation. Hence, the repetition of the carried-out work under differentially textured soils/agroclimatic conditions is quite difficult. As far as the calculative part, different lysimeters were installed in different plots receiving

*Step-wise technique of evaporation delineation with mini-lysimeters (a) Fitting of lysimeter in experimental plot, (b) use of chain-pulley for removing it from plots, (c) removed lysimeter, (d) weighing of lysimeters within*

the outer PVC pipe.

**Figure 9.**

**13**

*the plots receiving differential treatments [23].*

*3.3.1 Delineation of calculations of evaporation*

*DOI: http://dx.doi.org/10.5772/intechopen.92587*

differently established methods/techniques.

#### **Figure 8.** *Area Velocity Flow Meter for calculating the irrigation water applied.*

in the plastic pipe. When water applied to a particular plot equipped by a particular treatment, sensor placed in the pipe starts recording and displaying the quantity of water entered in the plot in liters which could be further be used in calculating the irrigation water productivity of differently treated plots. As there is no electric supply in the remote agricultural fields, hence a battery is required for its power. Further, calibrations are required before using it by filling the water in a Known volume of drum and in case of any discrepancy, a correction factor must be applied for further calculations for applied irrigation amounts in the agricultural water management experiments so that correct irrigation water productivities will be delineated under different treatments.
