**2. Method for assessing the process water footprint of growing selected crops**

#### **2.1. Site biophysical characteristics and crop management**

Water footprint study of the process of growing crops was conducted at Massey University's Pasture and Crop Research Unit, Palmerston North, between November, 2009 and April, 2011. Massey University is located at a latitude of 40°22′ 54.02 S, longitude 175°36′ 22.80 E, and an altitude of 36 m a.s.l. The soil type is Manawatu sandy loam with Olsen P at 36 mg/L; K at 0.22 mg/100 g, available N at 106 kg ha−1 and anaerobically mineralised N kg−1 at 76.8 mg at the beginning of the experiment. Climatic data for the site is in **Figure 1**.

The study crops were managed at both supplementary irrigation and rain-fed conditions. There were four cultivars of potato (*Solanum tuberosum* L., *Solanum andigena* Juz & Buk.), two of oca (*Oxalis tuberosa* Mol.) and two of pumpkin squash (*Curcubita pepo* Linn and *Cucurbuta maxima* Duchesne) in each water regime. Rainfall treatment measured green water (rain water) while supplementary irrigation measured both green and blue water footprint (water from river, sea or ocean or ground) [12]. The four-selected potato cultivars included two modern cultivars (Agria and Moonlight (*S. tuberosum* L.)) and two heritage cultivars (Moe Moe (*S. tuberosum* L.) and Tutaekuri (*S. andigena* Juz & Buk.)). The two selected pumpkin squash cultivars included buttercup squash, Ebisu (*C. maxima* Duchesne, a modern cultivar) and Kamokamo (*C. pepo* Linn, a heritage cultivar), while two unnamed oca cultivars with dark orange and scarlet coloured tubers were used.

All crop husbandry practices were followed in potato, oca (3.3 plants m−2) and pumpkin squash (2.2 plants m−2). Potatoes and oca received 12 N:5.2 P:14 K:6 S + 2 Mg + 5 Ca, using 500 kg ha−1 Nitrophoska Blue TE at planting, followed by 100 kg N ha−1 of urea 21 days later. The pumpkin squash received 12 N:5.2 P:14 K:6 S + 2 Mg + 5 Ca, using 700 kg ha−1 Nitrophoska Blue TE at planting, followed by 66 kg N ha−1, when the vines started running. Pests and diseases were also controlled accordingly [13].

#### **2.2. Irrigation and crop water use measurement**

evaporation, in addition to environmental pollution are accelerating [4]. Until the recent past, there has been little attention to how water is consumed and polluted in agriculture in New Zealand. As a result, the profitability of traditionally irrigated crops reduced [5]. Improved understanding of water footprint (WF) differences in cultivars can reduce the pressure on freshwater, while still maintaining their profits and sustaining the environment. This can be achieved if farmers can start using water sparingly under both modern and heritage crop cultivars [6].

Information on water footprint differences in selected heritage cultivars used by Maori for over 200 years is of significant importance because of their social and cultural value to the economy [7]. McFarlane stated that these heritage cultivars attract a niche market and provide a cultural economy [8]. For instance, the Taewa Maori potato and Kamokamo are a treasured heritage used to enforce land rights, values and sustainable development in New Zealand [9]. Lately, modern crop cultivars have made a significant advancement in productivity, above heritage cultivars. The increased interest in heritage cultivars is restricted by a lack of information on their water use. There is need of information on new ways to grow heritage or modern crops while leaving more water available for people, plants and animals. Idea of considering water use along supply chain can be well explained by the concept of water footprint (WF).

or volume of specific crop [10]. It is a multidimensional indicator showing water consumption volumes by source and polluted volumes by type of pollution where all components of total water footprint are specified geographically and temporally. This footprint is an important factor in future market access, water conservation and growing international trade in agriculture [11]. The study and literature on water footprint expose hidden uses of water resources in producing a crop product over a complete supply chain (producers to consumers). Discovery of such hidden links can form basis for the formulation of new strategies of water governance among growers and consumers. The knowledge of water footprint to final consumers, retailers, food industries and traders in water—intensive products can make them become agent of change in promoting sparing water use. Nevertheless, the water footprint of arable crops has not been sufficiently examined among standard and heritage crop cultivars in New Zealand. In this chapter, we discuss the water footprint differences of producing selected heritage and modern potato, oca and pumpkin squash cultivars grown under rain-fed and irrigated conditions, in New Zealand;

and finally what the WF means in the context of the social-economic aspects of growers.

Water footprint study of the process of growing crops was conducted at Massey University's Pasture and Crop Research Unit, Palmerston North, between November, 2009 and April, 2011. Massey University is located at a latitude of 40°22′ 54.02 S, longitude 175°36′ 22.80 E, and an altitude of 36 m a.s.l. The soil type is Manawatu sandy loam with Olsen P at 36 mg/L; K at 0.22

**2. Method for assessing the process water footprint of growing** 

**2.1. Site biophysical characteristics and crop management**

ton−1) is defined as the volume of water required to produce a given weight

**1.1. Definition and significance of water footprint**

Water footprint (m3

88 Irrigation in Agroecosystems

**selected crops**

In order to measure the actual water use, a soil water balance was used to determine the soil moisture deficit (SMD) on a daily basis during the growth of the crops [14]. The potential evapotranspiration (ETp) in the soil water balance was computed using the FAO 56 Penman-Monteith method [15, 16]. The crop coefficient factors used in the computation were for potato, because this was the most sensitive crop to water use [17]. NIWA/Ag Research in Palmerston North provided daily weather data for running the soil water balance model. The soil water balance model helped to scheduling irrigation centering on refilling 25 mm of the soil moisture deficit when it reaches 30 mm. It was made sure that approximately half the readily available water was supplied. An equation of actual crop evapotranspiration (ET<sup>c</sup> ) was used as in Eq. (1) [15]. Soil moisture was monitored using time-domain reflectometer (TDR) to determine soil moisture change (∆S) [13] and surface runoff (R<sup>o</sup> ) was negligible.

$$\text{ET}\_c = \text{P} + \text{I} - \text{D}\_p - \text{R}\_o + \Delta \text{S} \tag{1}$$

Consumptive water use (CWU) for the entire growing cycle, for irrigation and rain-fed treatments, were referred to as blue and green components, respectively. The CWU was determined according to Hoekstra [10], as in Eq. (2), where ∑ETcblue and ∑ETcgreen is the accumulation of actual water use (evapotranspiration) over the complete growing cycle for irrigated and rain-fed crops, respectively. Factor of 10 was required to convert water depths of mm into volume in m<sup>3</sup> ha−1 [10].

respectively. Factor of 10 was required to convert water depths of mm into volume in m ${}^{3}$ ha ${}^{1}$ [10].

$$\begin{array}{l} \text{CWU}\_{\text{blue};\text{green}} = 10 \times \sum \text{ETcblue} + \text{ETcgreen} \\ \text{CWU}\_{\text{green}} = 10 \times \sum \text{ETgreen} \end{array} \tag{2}$$

**2.3. Determination of water footprint differences of cultivars of selected crops**

green and grey water footprint. Blue and green water footprint (m<sup>3</sup>

crop and crop water requirements are used [22, 23].

**2.4. Social-economic analysis of the selected crop cultivar**

determine their comparative water footprint differences.

**3.1. Crop water use and yield summary**

evapotranspiration, thus crop coefficient (k<sup>c</sup>

the total yield or total biomass yield (t ha−1) [10]. Total water footprint was the sum of blue,

and green crop water use (mm), to the total yield or total biomass yield (t ha−1), respectively

required diluting nitrogen that reached the ground water, per ton of produce [19]. Grey water footprint was estimated by multiplying the leaching fraction by the nitrogen application (kg ha−1) and dividing the difference between the permissible limit and the natural concentration of nitrogen in the receiving water body. The study assumed a natural water nitrate

−1 and the permissible limit of 11.3 mg l

assumed at 10% [18, 21]. This study compared the water footprint based on actual crop yield and crop water use, in order to remove the disparity of over-estimation, once hypothetical

An economic assessment of Taewa against modern potato varieties in relation to irrigation investments was done using the net present value (NPV) method. Net present value is an investment analysis also referred as a total of present value of a single project cashflow of the same unit [24]. In order to get NPV, fixed and annual operating costs and expected returns were estimated based on a 5-ha small scale irrigation using a Trail Travel Irrigator to obtain the economic implications of the system on crop production. The data in the study on marketable fresh tuber or marketable fruit yield were used to analyse the economics of Taewa and water footprint. Crop water use and total yield from the three crops were pooled, in order to

Total consumptive water use (blue plus green water) for oca, potato and pumpkin squash in rain-fed and irrigation ranged from 5061 to 6824, 3470 to 5685 and 2551 to 4132 m<sup>3</sup> ha−1, respectively. Consumptive water use (m3 ha−1) was greatest in oca and lowest in pumpkin squash, while potatoes were intermediate, despite variation within cultivars. The modern and heritage crops differed in their relationship between their maximum water requirement and actual

used more water compared to modern cultivars (**Table 1**). Green water was approximately 62, 65, 58 and 70% of consumptive water use, under irrigated modern potato, Taewa, pumpkin squash and oca, respectively. Blue water for oca and potato was 2000 m<sup>3</sup> ha−1, while pumpkin squash received 1750 m<sup>3</sup> ha−1, applied to meet at least 100% of the crop's water requirement. Grey water also significantly differed between cultivars with the highest in potato and oca. An equivalency of diluting requirement to the grey water for the applied N in potato or oca and

) and maturity (**Figure 2**). Taewa and Kamokamo

t ha−1) was determined as the ratio of actual crop water use (m3 ha−1) to

Water Footprint Differences of Producing Cultivars of Selected Crops in New Zealand

t ha−1) was determined as a ratio of total volume of water (m3

t ha−1) was a ratio of blue

http://dx.doi.org/10.5772/intechopen.77509

−1 [20]. Leaching fraction was

)

91

Water footprint (m3

[18]. Grey water footprint (m3

concentration of 5.6 mg l

**3. Results**

**Figure 1.** Soil moisture change in heritage and modern potato, oca and pumpkin squash cultivars under irrigation and rain-fed conditions.
