Compost can reduce evaporation and increase nutrient uptake by plants, but it is not clear if it can increase soil water holding capacity or stimulate leaf gas exchange, water use efficiency and yield of vines. To study these effects, compost from garden and food waste was incorporated or mulched in a vineyard at a rate of 100 m 3 ha -1 , three months before the measurements. The vineyard received irrigation during spring and summer. Soil water content was monitored regularly with a capacitance probe. Photosynthesis, transpiration, stem water potential and leaf area index were measured several times during the vegetation period. At harvest, yield, berry weight and quality as well as chlorophyll, N, P and K concentrations in leaves were determined. Only mulched compost increased soil water content at 10 cm depth, but the water content in the deeper layers was not affected by compost addition. Compost also did not affect transpiration rate and stomatal conductance during the vegetation period, but mulched compost increased the photosynthesis per plant at flowering, pea size and maturity periods. Compost amendment, particularly mulching, increased yield, specific berry weight, and leaf N and P concentrations, and reduced the number of chlorotic leaves at harvest. Berry quality was not affected by compost amendment. It can be concluded that mulched compost has a positive effect on grapevine yield and can be an alternative fertiliser source for vines with no adverse effect on berry quality.

No abstract

Compost addition to soil can increase nutrient availability, but if added to sandy soils, nutrients can be rapidly leached. Clay added to compost could increase nutrient retention and reduce nutrient leaching due to binding to the clay. An incubation experiment was conducted to assess the effect of addition of a fine-textured soil (34% clay) to garden waste compost on nutrient availability and leaching in a sandy soil. The sandy soil was non-amended or amended with compost only, at a rate 27.3 g kg–1, or with a mixture of compost and 5% or 20% (w/w) of fine-textured soil. Two additional treatments included sandy soil amended with only the fine-textured soil at rates similar to those added with compost. Soil, compost, and fine-textured soil were mixed and packed to a bulk density of 1.22 g cm–3. Soil respiration was measured over 23 days. On days 1, 5, and 23, the soils were leached with 50 mL reverse-osmosis water, and the following parameters were measured in the leachate: water-soluble organic carbon (OC), inorganic nitrogen (N), and phosphorus (P); water-soluble OC and available N and P were measured in the soil after leaching. Compost increased nutrient availability and leaching compared with the non-amended control. Addition of the fine-textured soil to compost reduced cumulative respiration and N and P leaching, with the effect more pronounced at 20% (w/w). Addition of the fine-textured soil alone had no effect on nutrient availability and leaching because of the low nutrient concentration in this soil. This study showed that addition of fine-textured soil to compost can reduce N and P leaching, which could enhance and prolong the positive effects of compost on soil fertility.

No abstract