Effects of vertical distribution of soil inorganic nitrogen on root growth and subsequent nitrogen uptake by field vegetable crops

Information is needed about root growth and N uptake of crops under different soil conditions to increase nitrogen use efficiency in horticultural production. The purpose of this study was to investigate if differences in vertical distribution of soil nitrogen (Ninorg) affected root growth and N uptake of a variety of horticultural crops. Two field experiments were performed each over 2 years with shallow or deep placement of soil Ninorg obtained by management of cover crops. Vegetable crops of leek, potato, Chinese cabbage, beetroot, summer squash and white cabbage reached root depths of 0.5, 0.7, 1.3, 1.9, 1.9 and more than 2.4 m, respectively, at harvest, and showed rates of root depth penetration from 0.2 to 1.5 mm day)1 C)1. Shallow placement of soil Ninorg resulted in greater N uptake in the shallow-rooted leek and potato. Deep placement of soil Ninorg resulted in greater rates of root depth penetration in the deep-rooted Chinese cabbage, summer squash and white cabbage, which increased their depth by 0.2–0.4 m. The root frequency was decreased in shallow soil layers (white cabbage) and increased in deep soil layers (Chinese cabbage, summer squash and white cabbage). The influence of vertical distribution of soil Ninorg on root distribution and capacity for depletion of soil Ninorg was much less than the effect of inherent differences between species. Thus, knowledge about differences in root growth between species should be used when designing crop rotations with high N use efficiency

Root penetration of strong soil in rainfed lowland rice: comparison of laboratory screens with field performance

Rice cvs with better hardpan penetration would be expected to be more drought resistant in the rainfed lowlands. Although laboratory methods to facilitate the identification or breeding of cvs with good root-penetration ability have been described, there is a need to validate such screens against field performance. Here, we compare previous field measurements with laboratory screening measurements in eight cvs (IR20, CT9993, KDML 105, IR58821, NSG 19, IR62266, Mahsuri and IR52561). These were screened (together with Moroberekan, SG329 and IR36 for comparative purposes) using a flooded wax-layer screen. Of the eight cvs, IR58821 gave the best penetration of a 60% wax layer, with a mean penetration of 5.8 root axes per plant. The worst performer was IR52561, with a mean of 0.6 axes per plant. The cvs IR20, CT9993, KDML 105, IR58821 were also screened (together with Azucena, Bala, Moroberekan, Kinandang Patong and IR36 for comparative purposes) using a (non-flooded) sandcore screen. The sand-core screen allowed mechanical impedance of the whole sand core to be varied independently of aeration and water status. High impedance treatments were obtained by placing weights on the sand cores, which greatly decreased root growth, although differences between cvs in response to impedance in the sand-core screen were small. The ability of rice roots to penetrate wax layers did not appear to be related to their elongation through strong sand, but rather to their ability to resist buckling on encountering the wax layer. Comparison with field measurements showed that cvs with good performance in the wax-layer screen did not necessarily have good hardpan penetration in the field, although IR58821 was the best performer in the field. It is concluded that further work is required to compare root penetration in the field with root penetration in laboratory screens. (C) 2002 Elsevier Science B.V. All rights reserved

Plant and soil testing to assess the adequacy of phosphorus supply to winter oilseed rape

Includes bibliographical referencesAvailable from British Library Document Supply Centre- DSC:6924. 8597(no 58) / BLDSC - British Library Document Supply CentreSIGLEGBUnited Kingdo