稻壳炭对紧实土壤中苹果根系硫同化酶活性、H2S含量及根系构型的影响

  【目的】   苹果种植后土壤很少翻动，根系常受土壤紧实胁迫。研究在土壤中掺混稻壳炭提高苹果根系硫同化代谢以及根系构型的效果，为果园土壤管理提供技术参考。   【方法】   以砧木分别为平邑甜茶和八棱海棠的两年生‘红富士’苹果 (Malusdomestica ‘Red Fuji’) 幼树为试材进行盆栽试验。对掺入和没掺入稻壳炭的土壤分别进行镇压 (土壤紧实度值分别为1558和1572 KPa) 和不镇压 (土壤紧实度值分别为923和939 KPa)，共4个处理。苹果幼树移栽成活后60天，测定土壤孔隙度、氧气浓度和水溶性硫含量，分析苹果根系硫酸根和硫化氢 (H₂S) 含量及ATP硫酸化酶 (ATPS)、O-乙酰丝氨酸裂解酶 (OASTL) 和L-半胱氨酸脱巯基酶（L-CD）、D-半胱氨酸脱巯基酶 (D-CD) 活性，以及根系活力和形态构型等。   【结果】   镇压处理显著降低了土壤中水溶性硫含量，降低了八棱海棠和平邑甜茶为砧木的苹果幼树根系硫酸根含量，降低了根系ATPS、OASTL和L-CD、D-CD活性以及内源H₂S含量，并显著降低根系活力、根长密度、根系长度、根系体积和根系分形维数，在平邑甜茶为砧木的幼树根系中的降低幅度大于八棱海棠砧木。无论是否镇压土壤，掺入稻壳炭均提高了土壤孔隙度、土壤氧气浓度以及不同形态硫含量，提高了苹果根系硫酸根和内源H₂S含量，根系ATPS、OASTL和L-CD、D-CD活性，根系活力，根系长度，根长密度和根系分形维数，且在紧实土壤中八棱海棠砧木的提升幅度大于在平邑甜茶砧木中，两种砧木的苹果幼树在紧实土壤中的提升幅度均大于在正常土壤中。   【结论】   土壤紧实显著降低土壤水溶性硫含量，抑制苹果根系硫代谢和根系生长，在土壤中掺入稻壳炭可以显著提高紧实土壤中苹果根系硫代谢、根系生长和根系分枝。因此，在苹果移栽时，在土壤中掺入一定比例的稻壳炭可以有效缓解土壤紧实对苹果根系生长和硫代谢的不利影响。

Effects of rice husk biochar on enzyme of sulfur assimilation,H2S content and root architecture of apple trees in compacted soil

  【Objectives】   Apple orchard soil is least disturbed after transplanting of apple trees, so the soil often becomes compacted after years’ growth. We studied the effects of rice husk biochar on reversing the adverse impaction.   【Methods】   Two-year old potted apple trees (Malusdomestica ‘Red Fuji’) were used as the test material, with two types of rootstocks of Malushupehensis var. pingyiensis Jiang and Malusrobusta Rehd, respectively. The pot soil was subjected respectively to four treatments, mixed with or without rice husk biochar, compacted or not compacted. After the apple trees grew for 60 days, the soil porosity, oxygen concentration, sulfur fraction contents were analyzed. The apple root sulfate and H₂S content and the sulfur metabolism related enzyme activities, and root activity and root architecture were measured.   【Results】   Soil compaction significantly decreased the content of water soluble sulfur, sulfate and H₂S, and the activities of ATP sulfurylase (ATPS), O-acetylserine (thiol) lyase (OASTL) and L-cysteine desulfhydrase, D-cysteine desulfhydrase (L-CD, D-CD), and decreased apple root activity, root length density, root length, root volume and root fractal dimension. The decreases for the roots of M. hupehensis var. pingyiensis as the rootstock were higher than those of the rootstock of M. robusta. Compared with the treatment without rice husk biochar, the soil porosity, soil oxygen concentration, contents of water soluble sulfur, sulfate and H₂S in roots, and the activity of ATPS, OASTL and L-CD, D-CD in roots, root activity, root length, root length density and root fractal dimension were all improved in treatment with rice husk biochar under the normal or compact soils. The increases for the rootstock of M. robusta were higher than M. hupehensis var. pingyiensis under the compact soils, and that of the young apple of two rootstocks in the compact soil was greater than in the normal soil.   【Conclusions】   Soil compaction significantly decreases the content of water soluble sulfur in soil and inhibites apple root sulfur metabolism and growth. Addition of rice husk biochar can significantly alleviate the adverse impaction, and improve root growth. Therefore, it is recommended to add rice husk biochar in soil before transplanting of apple trees.