Responses of soil properties, crop yield and root growth to improved irrigation and N fertilization, soil tillage and compost addition in a pepper crop

Two improved management packages of tillage, irrigation, and nitrogen (N) management were compared with conventional management (CM), in a sweet pepper crop, in a plastic greenhouse in southeastern Spain. Crops were grown in a layered “enarenado” soil. The two improved packages included prescriptive and corrective irrigation management using, respectively, the PrHo program and tensiometers, and prescriptive N management using the VegSyst-DSS program. In both improved packages, soil was tilled to 10 cm prior to transplanting after temporarily removing the sand mulch layer. In one of the improved packages, the “reduced input and tillage plus compost” (RIT + C), compost was incorporated during tillage. In the other improved package, the “reduced input and tillage” (RIT), no compost was added; otherwise, management was identical in both improved packages. Total volumes of applied irrigation and of drainage, and the total amounts of applied N were reduced in RIT and RIT + C compared to CM. However, the RIT and RIT + C packages were associated with slightly less fruit production than CM. This was attributed to higher root zone salinity and an apparent slight N deficiency. Biomass, fruit production and root growth were lowest in RIT + C, which were attributed to salts added in the compost. Relative to the untilled CM soil, soil tillage in the RIT package reduced soil bulk density and favoured deeper root growth. Compared to RIT, compost addition in RIT + C was associated with less root growth presumably because of higher salinity. To optimize N management, the use of N monitoring during the crop (i.e. corrective management of N) is required when prescriptive N management is being used. Long term practices of tillage and organic matter addition may be required to appreciably improve soil quality in this agricultural system. Care may have to be taken to ensure that excessive quantities of salts are not added when applying compost.