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<p style="text-align: justify;"><strong>Aim</strong>: To compare grape yield prediction methods to determine which provide the best results in terms of earliness of prediction in the growing season, accuracy and precision.</p><p style="text-align: justify;"><strong>Methods and results</strong>: The grape yields predicted by six models – one for use at fruitset (FS), two for use at <em>veraison</em> (V1 and V2), and three for use during the lag phase (LP40, LP50 and LP60) – were compared to field-measured yields. Regressions for the yield predicted by each model were constructed. The V1 and V2 models had the highest R² (0.75) and efficiency index (EF; 0.67-0.71) and the lowest RMSE values (±16-17%, or &lt;0.5 kg per m of row). The FS model had the same or similar R² (0.58), EF (0.06) and RMSE (±30%, or &lt;0.83 kg per m of row) values as the LP models, but allowed yield predictions to be made one month earlier.</p><p style="text-align: justify;"><strong>Conclusion</strong>: The validated FS, V1 and V2 models are all useful in predicting grape yields and could be used to accurately forecast (with different errors) grape yields at either early or later time points according to winery needs. These models could be improved as further data become available in following seasons.</p><p style="text-align: justify;"><strong>Significance and impact of the study</strong>: Few validated models are available for predicting grapevine yields at fruitset and <em>veraison</em>. This study provides predictive models that can be used at these different times of the growth cycle.<strong></strong></p>

Abstract. Cover crops in Mediterranean vineyards are scarcely used due to water competition between the cover crop and the grapevine; however, bare soil management through tillage or herbicides tends to have negative effects on the soil over time (organic matter decrease, soil structure and soil fertility degradation, compaction, etc). The objective of this study was to understand how soil management affects soil fertility, compaction and infiltration over time. To this end, two bare soil techniques were compared, tillage (TT) and total herbicide (HT) with two cover crops; annual cereal (CT) and annual grass (AGT), established for 8 years. CT treatment showed the highest organic matter content, having the biggest amount of biomass incorporated into the soil. The annual adventitious vegetation in TT treatment (568 kg dry matter ha-1) that was incorporated into the soil, kept the organic matter content higher than HT levels and close to AGT level, in spite of the greater aboveground annual biomass production of this treatment (3632 kg dry matter ha-1) whereas only its roots were incorporated into the soil. TT presented the highest bulk density under the tractor track lines and a greatest resistance to penetration (at 0.2 m depth). AGT presented bulk density values (upper 0.4 m) lower than TT and penetration resistance in CT lower (at 0.20 m depth) than TT too. The HT decreased water infiltration due to a superficial crust generated for this treatment. These results indicate that the use of annual grass cover can be a good choice of soil management in Mediterranean climate due to soil quality improvement, with low competition and simple management.

Vineyard leaf area is a variable that must be determined when assessing the productive potential of a vineyard and for characterizing the light and thermal microenvironments of grapevine plants. The aim of the present work was to validate the Lopes and Pinto method for determining vineyard leaf area in the vineyards of central Spain and with the area's cultivars. The results obtained were compared to those provided by a traditional and accurate -but much more laborious-non-destructive direct method. Experiments were performed over three years in six vineyards growing either cvs. Syrah, Cabernet Sauvignon, Cabernet franc, Merlot or Tempranillo. Good agreement was found between the two methods both in the determination of primary and lateral shoot leaf areas for all cultivars and vineyards. The simplicity of the Lopes and Pinto method means much larger sample sizes can be examined in the same period of time, increasing the accuracy of final vineyard leaf area values. In fact, regression analysis of the data collected for the Lopes and Pinto method showed that only three field-measured variables need to be recorded for the inspected shoots of either type: the area of the largest leaf, the area of the smallest leaf, and the number of leaves.Additional key words: Cabernet franc; Cabernet Sauvignon; destructive methods; Merlot; non-destructive methods; Syrah; Tempranillo; Vitis vinifera. Resumen Estimación del área foliar del viñedo mediante regresión linealEn viticultura, el área foliar del viñedo es una variable que debe ser determinada para evaluar el potencial productivo del viñedo, para caracterizar el microclima luminoso y térmico de la vid. El objetivo del presente trabajo fue validar el método propuesto por Lopes y Pinto para determinar el área foliar de viñedos del centro de España y con cultivares de la zona. Los resultados obtenidos fueron comparados con los obtenidos por un método directo no destructivo y preciso, más tradicional pero mucho más laborioso. Los ensayos se llevaron a cabo con los cultivares Syrah, Cabernet Sauvignon, Cabernet franc, Merlot y Tempranillo en seis viñedos durante tres años. Entre ambos métodos se observó un buen ajuste, tanto para la determinación del área foliar de principal como para la de nietos, en todos los cultivares y viñedos. La simplicidad del método de Lopes y Pinto permite incrementar el tamaño de muestra para un mismo tiempo de muestreo, incrementando así la precisión del valor final del área foliar del viñedo. Efectivamente, el análisis estadístico de los datos recogidos para el método de Lopes y Pinto mostró que sólo es necesario medir tres variables en campo: el área de la hoja más grande, el área de la hoja más pequeña y el número de hojas, para principal y para nietos separadamente.