Abstract
Information about the nutrients distribution in sand-mulched soils is rather scarce; therefore, the aim of this experiment was to determine the spatial distribution and mobility of macronutrients in the wet bulb zone in two sand-mulched soils (a technique where manure and sand are layered over existing soil) for fertigated green bean with a drip irrigation distribution system under greenhouse conditions. The experimental design was multifactorial (4): soil type (S1 (1.0% organic matter (OM)) and S2 (2.5% OM)), time of sampling (before planting and after crop harvest) and spatial distribution: distance (0.1, 0.2, and 0.3 m) from the emitter and soil depth (0.1–0.2, 0.2–0.3 and 0.3–0.4 m) with three blocks and one replication per block. The chemical parameters (pH, electrical conductivity (EC), and macronutrients concentration) were analyzed in each soil sample. The testing crop was green bean (Phaseolous vulgaris L. c.v. Mantra RZ), lasting 90 days. The results obtained showed the highest value of EC and NO3−-N, K, and Ca concentration in the sand layer in both soils. At all soil profile depths, nutrient concentrations of NH4+-N and soil EC were lower in the high OM soil. Comparing the soil profile at the beginning and at the end of the experiment, there was a significant decrease in NO3−-N, P and Ca concentration and a significant increase in EC value and Mg concentration at the end of the crop. In distance, EC and K showed the highest concentration at 0.30 m. In depth, there was a decline in EC value and NH4+-N, P, K, Ca and Mg concentration. The comparison between the sand layer and the soil profile in both soils reported a similar trend in pH, EC, NO3−-N, P and Mg concentration. Considering the mobility of macronutrients in a sandy mulched soil, it would be recommendable to develop a sustainable and dynamic fertigation management, adjusting nutrient inputs over time.
Highlights
The higher values of Electrical conductivity (EC) in sand layer compared to the soil profile in our experiment can be ascribed to the retention of salts by sand in the evaporation process [31], which depends on the abrupt changes in pore size that affect water movement by capillary action
It is concluded that green bean cultivated in sand mulching soil under fertigation showed an accumulation of NO3 − -N, K, and Ca concentration at the end of the crop in the sand layer in both soils, and increased EC, showing the highest value on the periphery of the bulb at 0.30 m
Along the crop, there was a significant decrease in NO3 − -N, P and Ca concentration and a significant increase in EC value and Mg concentration
Summary
Southern Spain is one of the most important areas of intensive horticultural crops in Europe, with 31,614 ha of greenhouses, in which Almeria represents around 86% of total greenhouses [1] Agricultural practices such as the use of sand mulching soil and fertigation are common in this region [2]. Sand mulching soil has been used by local growers to develop favorable conditions for the maintenance of horticultural crop growth in semiarid conditions [3]. This system is composed by sand mulching and artificial soil profile, which can be classified as a cumulic Anthrosol [4]. The positive effects of mulches in soil, such as evapotranspiration reduction and the improvement of the root system, have been reviewed recently in detail by several authors [7,8]
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