Step 1: Recall why a slope limit exists for surface irrigation at all.
In border and furrow irrigation, gravity alone moves the water sheet down the field. If the land is too flat the water moves too slowly and ponds, causing waterlogging and uneven advance, and if it is too steep the water races down, causing scour and poor uniformity. Every soil texture class has its own safe slope band that balances these two failure modes.
Step 2: Compare the three broad soil texture classes side by side.
Coarse sandy soils drain fast, so they tolerate a comparatively steeper slope, roughly 0.5 to 2 percent, without the water stalling. Fine clayey soils drain very slowly, so they need a nearly flat field, roughly 0.05 to 0.2 percent, or the water cannot spread before it erodes the surface. Medium loamy soils sit in between these two extremes on both counts.
Step 3: Place the loam value in the middle band and check it against the options.
Since loam is intermediate in both infiltration rate and erosion resistance, its safe slope range should also sit between the sandy and clayey figures, which puts it at about 0.20 to 0.40 percent. The option showing 0.05 to 0.20 is the clay range and 0.70 to 0.90 is far too steep for any irrigated soil, so the only value consistent with loam's intermediate behaviour is 0.20 to 0.40.
\[ \boxed{0.20 \text{ to } 0.40} \]