Response of P, K, Mg and NO3-N contents of carrots to irrigation, soil compaction, and nitrogen fertilisation

Soils ploughed in autumn were loosened by different tillage tools, or compa cted 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. Sprink ler 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 add itional N application of 30 kg ha(-1) was studied in an organic soil. Highe r soil moisture tended to promote nutrient uptake, as the P content of carr ot tap roots was increased by irrigation in loam. Compaction of organic soi l 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 m g kg(-1) fresh matter) and decreased with advancing season. In loam, NO3-N content was increased by irrigation or loosening. Increasing the N fertilis ation 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 gr owth stage had much more significant influence on the P, K, and Mg contents of carrots than soil treatments.