**1. Introduction**

The agricultural industry in New Zealand consumes 77% of the freshwater resources [1]. Climate change alongside population and urbanisation has broaden this demand by increasing water utilisation per capita [2]. Water consumption and pollution associated with agriculture has created a great competition for water [3]. As of now groundwater withdrawal and rainwater

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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].

mg/100 g, available N at 106 kg ha−1 and anaerobically mineralised N kg−1 at 76.8 mg at the

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

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

89

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

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

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

[15]. Soil moisture was monitored using time-domain reflectometer (TDR) to determine soil

ET<sup>c</sup> = P + I − Dp − Ro + ∆S (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].

CWUblue+green <sup>=</sup> <sup>10</sup> <sup>×</sup> ∑ETcblue <sup>+</sup> ETcgreen CWUgreen <sup>=</sup> <sup>10</sup> <sup>×</sup> ∑ETgreen (2)

) was negligible.

) was used as in Eq. (1)

water was supplied. An equation of actual crop evapotranspiration (ET<sup>c</sup>

beginning of the experiment. Climatic data for the site is in **Figure 1**.

orange and scarlet coloured tubers were used.

diseases were also controlled accordingly [13].

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

moisture change (∆S) [13] and surface runoff (R<sup>o</sup>

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).

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

Water footprint (m3 ton−1) is defined as the volume of water required to produce a given weight 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.
