ABSTRACT

Lupinus albus L. (lupine) has a high tolerance for phosphorus deficient conditions as its roots can solubilize the unavailable phosphorus in the rhizosphere soil. The roots may also be able to solubilize other elements, but this requires further investigation. In this study, therefore, we conducted two experiments to comprehensively investigate the effects of lupin roots on the mineral dynamics of the rhizosphere soil. First, a mixed cropping experiment was conducted, in which lupin shared a rhizosphere with soybean (Glycine max (L.) Merr.) in a long-term experimental field with four fertilizer treatments: complete fertilization (+NPK), without nitrogen (−N), without phosphorus (−P), and without potassium (−K). The results of shoot dry weight of plants cultivated alone indicated that lupin is highly tolerant to all N, P, and K deficiencies, while soybean can adapt to N deficiency with the help of rhizobia but is less tolerant to P and K deficiencies than lupin. When mixed-cropped with lupin, the concentrations of many elements in the soybean leaf increased, particularly with the −N and −P treatments. Furthermore, soybean growth was significantly improved when cropped with lupin in the −N and −P treatments. Second, a comparison of the elemental profiles of hydroponically and field-soil-grown plants was conducted. Under hydroponic conditions, the rhizosphere effect is negligible when the culture medium is well circulated. The lupin/soybean ratios for leaf mineral concentrations were considerably larger in the field cultivated plants when compared with the hydroponic cultivations for elements such as sodium, potassium, cesium, phosphorus, iron, copper, and molybdenum, as there were lower concentrations of these elements in the soybean leaves in the field. These results indicate that lupin roots can solubilize a variety of insoluble elements in the soil, which may be the reason why lupin can adapt to various nutrient deficient soils. In the lupin rhizosphere, the solubilization of cesium, which is generally strongly fixed by soil minerals and not easily leached, was particularly pronounced. This implies that the surface structure of clay minerals might be altered in the lupin rhizosphere, resulting in the fixed forms of various elements becoming available.

摘要

Lupinus albus L. (羽扇豆) 对缺磷条件有很高的耐受性，因为它的根可以溶解根际土壤中不可用的磷。根也可能能够溶解其他元素，但这需要进一步研究。因此，在本研究中，我们进行了两个实验，以全面研究羽扇豆根对根际土壤矿物动力学的影响。首先，进行了混作试验，其中羽扇豆与大豆（Glycine max(L.) Merr.) 在具有四种肥料处理的长期试验田中：完全施肥 (+NPK)、无氮 (-N)、无磷 (-P) 和无钾 (-K)。单独栽培植物的茎干重结果表明，羽扇豆对所有N、P、K缺乏具有高度耐受性，而大豆可以借助根瘤菌来适应N缺乏，但对P、K缺乏的耐受性不如羽扇豆。当与羽扇豆混作时，大豆叶片中许多元素的浓度增加，特别是在 -N 和 -P 处理下。此外，在 -N 和 -P 处理中与羽扇豆一起种植时，大豆生长显着改善。其次，对水培和田间土壤种植植物的元素分布进行了比较。在水培条件下，当培养基循环良好时，根际效应可以忽略不计。与钠、钾、铯、磷、铁、铜和钼等元素的水培栽培相比，田间栽培植物中叶片矿物质浓度的羽扇豆/大豆比率要大得多，因为这些元素的浓度较低在田间的大豆叶中。这些结果表明羽扇豆根可以溶解土壤中的多种不溶性元素，这可能是羽扇豆能够适应各种养分缺乏土壤的原因。在羽扇豆根际，铯的溶解作用特别明显，铯通常被土壤矿物质牢固固定，不易浸出。