Table 3 Equations used to calculate study parameters.

WUE = \(\:\frac{Total\:biomass}{TWA}\)

Where WUE is water use efficiency, total bio is above-ground biomass plus tuber biomass, and TWA is the total water applied

1

HI (%) = \(\:\frac{AGEB}{AGB}\:x\:100\)

HI is the harvest index (%); AGEB is the above-ground edible biomass (g m − 2); AGB is the total above-ground biomass (g m^− 2).

2

RGR = \(\:\frac{\left(\text{ln}M2-lnM1\right)}{t2-t1}\)

Where M1 and M2 represent initial and final biomass at times t1 and t2 respectively

3

RHR = \(\:\frac{\left(\text{ln}H2\:-\text{ln}H11\right)}{t2-t1}\)

Where H1 and H2 represent initial and final height at times t1 and t2 respectively.

4

\(\:FI\:=1-\text{exp\:}(-LAI\:x\:k)\)

Where FI is fractional interception (unit-less), LAI is the leaf area index, and k is the light extinction coefficient (unit-less).

5

LI = \(\:\text{F}\text{I}\:\text{x}\:\text{R}\text{s}\)

Where LI is light intercepted (MJ m − 2), Rs is total radiation (MJ m^− 2).

6

RUE = \(\:\frac{AGB}{\sum\:LI}\)

Where RUE is radiation use efficiency (g MJ − 1); AGB (g m-2); LI (MJ m^− 2).

7

NY = \(\:\left(\text{A}\text{G}\text{E}\text{B}\:\text{x}\:\text{N}\text{C}\right)\)

Where NY is nutritional yield (g ha^− 1); AGEB (g m^− 2); NC is nutritional content (mg g^− 1 ).

8