Response of P, K, Mg and NO 3 -N contents of carrots to irrigation, soil compaction, and nitrogen fertilisation

Abstract

Soils ploughed in autumn were loosened by different tillage tools, or compacted to a depth of 25-30 cm by a tractor weighing 3 Mg (once or three times) before seed bed preparation for carrot under moist soil condition. Sprinkler irrigation was also applied to mineral soils when the soil moisture in top soil was 50% of plant-available water capacity, and the response of additional N application of 30 kg ha-1 was studied in an organic soil. Higher soil moisture tended to promote nutrient uptake, as the P content of carrot tap roots was increased by irrigation in loam. Compaction of organic soil low in P increased P and K contents and uptake by carrot roots and shoots. In severely compacted clay soil, the nutrient use decreased by increasing soil compactness. NO3-N contents were the highest in early season (25-30 mg kg-1 fresh matter) and decreased with advancing season. In loam, NO3-N content was increased by irrigation or loosening. Increasing the N fertilisation of organic soil from 30 kg ha-1 to 60 kg ha-1 increased the NO3-N content 30%. Soil type and its nutrient status, weather conditions, and growth stage had much more significant influence on the P, K, and Mg contents of carrots than soil treatments