Table 4.
Components of the vineyard’s net primary production (NPP as t ha-1 of dry matter), the whole vine’s net carbon balance (NCB), and the vineyard’s net ecosystem carbon balance (NECB) calculated over the 2-year study for six different cover crop and tillage systems.a,b.
| Treatment | Harvest (Mg C ha-1) | Pruning wood (Mg C ha-1) | Leaves (Mg C ha-1) | Permanent organs (Mg C ha-1) | Grapevine NPP (Mg C ha-1 year-1) | Rs Under vine (Mg C ha-1 year-1) | Grapevine NCB (Mg C year-1) | Cover Crop NPP (Mg C ha-1) | Rs Interrow (Mg C ha-1 year-1) | SOC (Mg C ha-1) | NECB (Mg C ha-1 year-1) | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Tillage (T) | Cover crop (CC) | |||||||||||
| Fresno County (Five points) | ||||||||||||
| 2020 | ||||||||||||
| NT | AG | 1.39 | 1.76 | 3.02 | 11.5 | 17.7 | 1.84 | 15.35 | 1.80 | 2.81 | 17.71 | 23.36 |
| PG | 1.41 | 1.30 | 2.97 | 11.5 | 17.2 | 1.84 | 14.83 | 1.70 | 4.02 | 19.25 | 22.96 | |
| RV | 1.32 | 1.73 | 3.53 | 11.5 | 18.1 | 1.84 | 15.82 | 2.30 | 3.94 | 17.64 | 23.5 | |
| CT | AG | 1.25 | 1.75 | 3.22 | 11.5 | 17.7 | 1.84 | 15.54 | 3.93 | 3.39 | 19.81 | 25.31 |
| PG | 1.48 | 1.56 | 3.27 | 11.5 | 17.8 | 1.84 | 15.39 | 1.83 | 3.42 | 18.97 | 23.74 | |
| RV | 1.65 | 2.17 | 2.93 | 11.5 | 18.3 | 1.84 | 15.66 | 1.17 | 3.74 | 17.64 | 22.89 | |
| 2021 | ||||||||||||
| NT | AG | 1.24 | 1.61 | 2.98 | 11.5 | 17.3 | 2.96 | 14.56 | 2.00 | 3.71 | 17.71 | 22.24 |
| PG | 1.63 | 1.25 | 2.92 | 11.5 | 17.3 | 2.96 | 14.15 | 2.15 | 3.69 | 19.32 | 22.69 | |
| RV | 1.80 | 1.53 | 3.48 | 11.5 | 18.3 | 2.96 | 14.99 | 1.83 | 3.81 | 17.71 | 22.54 | |
| CT | AG | 1.11 | 1.75 | 3.18 | 11.5 | 17.6 | 2.96 | 14.91 | 4.08 | 5.81 | 19.88 | 23.63 |
| PG | 1.21 | 1.50 | 3.09 | 11.5 | 17.3 | 2.96 | 14.58 | 2.07 | 5.06 | 18.97 | 22.25 | |
| RV | 1.34 | 2.01 | 2.88 | 11.5 | 17.8 | 2.96 | 14.88 | 1.33 | 3.98 | 17.36 | 21.94 | |
| CC | ns | * | * | -- | ns | -- | ns | ** | ns | ns | ns | |
| T | ns | ns | ns | ns | ns | ns | ns | ns | ns | |||
| CC × T | ns | ns | ns | ns | ns | ns | ns | ns | ns | |||
| Year | ns | ns | ns | ns | * | * | ns | ns | ns | |||
| Year × CC | ns | ns | ns | ns | ns | ns | ns | ns | ns | |||
| Year × T | ns | ns | ns | ns | ns | ns | ns | ns | ns | |||
| Year × CC × T | ns | ns | ns | ns | ns | ns | ns | ns | ns | |||
| Napa County (Oakville) | ||||||||||||
| 2020 | ||||||||||||
| NT | AG | 0.15 | 0.37 | 0.57 | 6.7 | 7.8 | 3.71 | 5.71 | 2.92 | 5.56 | 29.25 | 18.49 |
| PG | 0.17 | 0.21 | 0.49 | 6.7 | 7.6 | 3.71 | 5.47 | 0.96 | 5.89 | 28.28 | 16.68 | |
| RV | 0.14 | 0.43 | 0.44 | 6.7 | 7.7 | 3.71 | 5.63 | 2.59 | 4.73 | 28.76 | 18.41 | |
| CT | AG | 0.16 | 0.51 | 0.55 | 6.7 | 7.9 | 3.71 | 5.83 | 2.96 | 6.85 | 29.25 | 18.00 |
| PG | 0.16 | 0.32 | 0.64 | 6.7 | 7.8 | 3.71 | 5.72 | 1.19 | 5.82 | 27.30 | 16.61 | |
| RV | 0.16 | 0.77 | 0.74 | 6.7 | 8.4 | 3.71 | 6.29 | 3.20 | 5.50 | 27.30 | 18.29 | |
| 2021 | ||||||||||||
| NT | AG | 0.44 | 0.56 | 0.61 | 7.0 | 8.6 | 4.40 | 5.88 | 3.20 | 7.25 | 28.76 | 17.74 |
| PG | 0.33 | 0.39 | 0.53 | 7.0 | 8.3 | 4.40 | 5.63 | 1.62 | 7.70 | 27.79 | 16.05 | |
| RV | 0.26 | 0.62 | 0.47 | 7.0 | 8.3 | 4.40 | 5.80 | 3.60 | 6.68 | 30.23 | 18.83 | |
| CT | AG | 0.37 | 0.68 | 0.58 | 7.0 | 8.6 | 4.40 | 5.97 | 3.32 | 7.48 | 27.30 | 17.08 |
| PG | 0.38 | 0.48 | 0.67 | 7.0 | 8.5 | 4.40 | 5.86 | 1.47 | 7.75 | 26.81 | 15.72 | |
| RV | 0.46 | 0.96 | 0.77 | 7.0 | 9.2 | 4.40 | 6.45 | 3.46 | 5.64 | 26.81 | 18.27 | |
| CC | ns | ns | ns | -- | * | -- | ** | ** | ns | ns | *** | |
| T | ns | ** | * | *** | *** | ns | ** | ** | * | |||
| CC × T | ns | ns | ns | * | * | ns | ns | ns | ns | |||
| Year | *** | ** | ns | *** | ns | ns | ns | ns | * | |||
| Year × CC | ns | ns | ns | ns | ns | ns | ns | ns | ns | |||
| Year × T | ns | ns | ns | ns | ns | ns | ns | ns | ns | |||
| Year × CC × T | ns | ns | ns | ns | ns | ns | ns | ns | ns | |||
a ANOVA was used to compare data (p-value indicated). Letters within columns indicate significant mean separation according to Tukey's honestly significant difference (HSD) test (at p = 0.05), where *: p-value < 0.05; **: p-value < 0.001, and ***: p-value < 0.0001. b NT, no tillage; CT, conventional tillage; AG, annual grass; RV, residual vegetation; PG, perennial grass; NPP; net primary production; NCB, net carbon balance; Rs, respiration; SOC, soil organic carbon; NECB, net ecosystem carbon balance; ns, not significant; and --: not applicable.