ABSTRACT

Comparison between organic and integrated vegetable crop production systems based on crop and soil parameters.

To improve the sustainability of vegetable production systems (organic and integrated production), and by using the experimental device set out in the framework of an European project which started in 1998, two experiments have been developed in the Experimental Center of the Ruralcaja Foundation in  Paiporta (Valencia): 1) a comparison of growing vegetables by using organic production versus integrated production over the period 2002-2005, and 2) a comparative assessment of three methods of management for crop residues: R1)  incorporation after a period of predecomposition on the soil surface; R2) withdrawal outside the plot; and, R3)  incorporation into the soil immediately after the harvest; this last experiment has elapsed in the period 2003-2006. 
Both systems consisted of four blocks or rotating blocks of rotation, and they have been cultivated with the same vegetable species: potato (Solanum tuberosum L.), var. Escort; fennel (Foeniculum dulce D.C.), var. Brando; maize (Zea mays L.), var. Challenguer; artichoke (Cynara scolymus L.), var. Lorca (1st and 2nd rotation), Blanca de Tudela / Aguadulce (3rd season) and Harmony (4th year); celery (Apium graveolens), var. Istar, and, watermelon (Citrullus vulgaris Schrad), being the variety used in the fifth seson F1 Graciosa, in the sixth and eighth rotation Boston (75%) / Dulce Maravilla (25%), and Boston (75%) / Andalusia ( 25%) in the seventh year. It has also been  grown cauliflower (Brassica oleracea), var. Pavilion, Sirente, Casper and Tipton; bean (Phaseolus vulgaris L.), var. Modus; and, lettuce (Lactuca sativa L.), var. RZ 41-66 were grown.
	Crops were irrigated by a drip irrigation system with underground water from a well, having a high nitrate content.
	Fertilization in the ecological system consisted in 20 t/ha  every two years of manure (50% beef + 50% sheep), and in the integrated system only phosphorus and potassium were provided in the form of phosphoric acid and potassium sulphate, respectively.
	For the control of pests and diseases in the ecological system, extracts from natural products and biological pesticides, authorized under the regulations for organic farming were used; and under integrated production, and in addition to organic products, some low environ mental impact pesticides, approved for this of cultivation system, were also applied.
The parameters controlled in both experiments were: marketable yield of crops, cull yield, average weight and dry matter and nutrients content in harvested products, macronutrient balance (only in experiment 1), and physicico-chemical, chemical, and biological soil properties. 
In experiment 1, the results found indicated that the overall yield under the organic production system was slightly lower than that under the integrated system, showing a decline of 11% in the average relative yield during the four years study. The cull yield was, on average, 36% higher in the ecological system. The average weight of the harvested products was quite similar in both production systems.
The contents of dry matter and nutrients in the products harvested throughout the period 2002-2005 showed wide variations depending on the crop, year, and production system; however, the mean differences between the two production systems were low. The simplified balance for macronutrients (N, P, K and Mg) gave positive values (surplus) in the two production systems; but in the organic system a comparatively higher surplus of N and Mg, and lower for K, were obtained, while it was similar in the case of P. Some characteristics of the soil layer 0-15 cm (organic matter, microbial biomass, and alkaline phosphatase and dehydrogenase activities) were quite altered by the fertilization program applied, with higher values in the organic system.
In experiment 2, the results obtained revealed that crop response to the incorporation of crop residues  varied widely depending on the vegetable species, with the largest positive response in fennel and the lowest one in cauliflower, although, in the set of all crops throughout the period 2003-2006, the average relative performance presented similar values in all three modes of management for crop residues.
Likewise, both cull yield and average weight of harvested products were slightly affected by the management procedure applied to the residues of the foregoing crop. The incorporation of the residual biomass, with respect to its withdrawal, caused significant increases in some soil characteristics in the 0-15 cm layer, mainly organic matter, organic nitrogen, nitrate nitrogen, available potassium, and biological activity (microbial biomass, dehydrogenase and alkaline phosphatase). And the parameter microbial biomass was more sensitive than organic matter, dehydrogenase or alkaline phosphatase activity as an indicator of soil changes resulting from the incorporation of crop waste biomass.