chemical and energy inputs required to reduce specific pest populations on specific hosts
Table 3–4. Selected indicators of sustainability for agroecosystems, and the indicator values for the conventional and agroforestry farms described in Table 3–5.
| Indicator | Definition | Value indicating high sustainability | Value indicating low sustainability | Conventional farm | Agroforestry farm |
|---|---|---|---|---|---|
| Harvest a | weight of harvested crops and livestock, kg ha−1 (lb acre−1) dry weight | 7,952 (7,100) | 0 | 3,805 (3,397) | 3,923 (3,503) |
| Cultural energy input b | total non‐solar energy inputs, MJ ha−1 (MJ acre−1) | 0 | 59,259 (24,000) | 17,264 (6,992) | 14,091 (5,707) |
| Energy output/input c | ratio of energy in harvested crops to cultural energy inputs | 5 | <1 | 3.9 | 4.5 |
| Energy capture efficiency d | energy in harvested crops as proportion of growing season PAR,% | 1.0 | 0 | 0.38 | 0.35 |
| Water use efficiency e | harvested biomass divided by AET (g m−1 mm−1) | 1.15 | 0 | 0.61 | 0.61 |
| Imported fertilizer f | N + P, kg ha−1 (lb acre−1) | 0 | 151 (135) | 44 (39) | 26 (23) |
| N losses g | losses through erosion and leaching), kg ha−1 (lb acre−1) | 0 | 45 (40) | 28 (25) | 20 (18) |
| Soil erosion h | wind + water, Mg ha−1 (tons acre−1) | 0 | 11 (8) | 11 (5) | 7.8 (2.5) |
| N balance i | N inputs/N outputs | 1 | <0.8 or >1.2 | 0.6 | 0.64 |
| P balance j | P inputs/P outputs | 1 | <0.8 or >1.2 | 0.7 | 0.46 |
| Crop diversity k | no. of crops per farm | 12 | 1 | 2 | 7 |
| Hired labor l | h ha−1 (h acre−1) | 0 | 5 (2) | 1 (0.4) | 5 (2) |
| Net income m | US$ ha−1 (US$ acre−1) | 235 (95) | 89 (36) | 99 (40) | 249 (101) |
| Capital borrowing n | debt/variable income | 0 | 1 | 0.63 | 0.46 |
| Farmer knowledge o | total skills and knowledge held by farm family | high | low | medium | high |
a High value is dry weight of grain from Nebraska irrigated corn (9406 kg ha−1 (150 bu A−1)).
b The value indicating low sustainability is the energy input per hectare to produce irrigated corn in Nebraska (Pimentel, 1980).