【作者】 刘炜；

【导师】 高亚军； 田霄鸿；

【作者基本信息】 西北农林科技大学 ， 植物营养学， 2007， 硕士

【摘要】 秸秆覆盖技术是当前世界旱农地区广泛推广的一项耕作技术。在我国,秸秆覆盖在传统农业中早有利用,近些年来在北方旱农地区迅速发展,成为少耕、免耕法的一个重要组成部分。作物正常的生长发育是地上部光合与地下部根群吸收水分、养分相统一的系统过程。土壤温度是重要的生态因子之一,它对植物生长发育的影响既是重要的农林问题,也是重要的理论问题。关于秸秆覆盖的土壤温度效应已有不少研究,但结果存在很多矛盾。覆盖条件下作物到底是增产还是减产?土壤温度是不是造成秸秆覆盖条件下小麦减产的主要原因?其作用机制又如何?对于这些问题尚未有合理的解释。本研究通过一个大田试验和两个水培试验,探讨了秸秆覆盖条件下的土壤温度效应及作物生长对根区温度的响应,获得了以下主要结论:(1)根据土壤日均温的变化特点,冬小麦田秸秆覆盖后至小麦收获之间的6个月可以分为4个阶段:冬前和越冬前期——土壤温度迅速下降阶段,越冬中期——土壤温度最低阶段,越冬后期至返青期——土壤温度缓慢上升阶段,拔节期至小麦生长后期——土壤温度持续上升阶段。秸秆覆盖使冬麦田昼夜平均温度显著升高,从冬前至返青期阶段,覆盖与无覆盖土壤昼夜平均温度差异越来越小,返青期后覆盖的增温效果则越来越明显:10 cm土壤温度最高可增加2.52℃,20 cm土壤温度最高可增加1.65℃。土壤10 cm温度从最低上升到最高需要6～9个小时,秸秆覆盖与无覆盖没有明显差异,拔节前秸秆覆盖显著降低了土壤温度日振幅,因此,秸秆覆盖土壤的升温速率和降温速率显著低于无覆盖土壤;拔节期至小麦生长后期秸秆覆盖的土壤温度日振幅显著高于无覆盖土壤,因此,秸秆覆盖的土壤升温和降温速率也都显著高于无覆盖土壤。冬前至返青期土壤20 cm昼夜平均温度均显著高于10 cm土壤,秸秆覆盖对其差异无显著影响;拔节期至小麦生长后期土壤20 cm昼夜平均温度则低于10 cm土壤,秸秆覆盖的差异显著高于无覆盖的差异。秸秆覆盖土壤最低温和最高温出现的时间与无覆盖一致。(2)与作为对照的常温处理相比,越冬前、越冬期和返青期低温和高温处理均在一定程度上影响了小麦的生长发育及养分吸收。越冬前低温处理对小麦根长没有显著影响,越冬期和返青期低温则抑制根长的增加;越冬前和越冬期高温均能促进根长增加,但返青期高温则不利于根长增加。与常温相比,越冬前低温抑制小麦生长,其中对地上部的影响大于对根系的影响;越冬前高温促进根系生长而不利于地上部干物质累积。越冬期低温也不利于小麦根系和地上部的生长;越冬期高温显著提高根系体积,对小麦地上部生长没有显著影响。返青期低温同样明显抑制小麦生长,对根系的影响稍大于地上部;高温主要影响小麦根系生长。三个时期内低温处理均明显抑制小麦整体对养分的吸收;越冬前高温降低了小麦的养分吸收量,越冬期高温也在一定程度上不利于养分吸收,返青期高温则有提高小麦地上部养分吸收的趋势。(3)越冬期常温条件下,1/2N水平处理(6 mmol·L-1)小麦根长高于正常N水平(12 mmol·L-1);低温条件下二者差异不大;高温条件下,1/2N水平处理小麦根长则略低于正常N水平。本水培试验条件下,氮素供应对小麦根系和地上部的生长影响不大。1/2N水平条件下,低温趋于减小根系干重、根系体积和地上部干重;高温则趋于促进小麦根系和地上部的生长。常温条件下,供氮水平降低对小麦的养分吸收没有明显影响。低温和高温条件下,供氮水平降低均显著影响小麦对养分的吸收。不论供氮水平如何,低温均显著降低小麦的养分吸收量,高温则显著提高养分的吸收量。不论供氮水平如何,高温可显著提高硝酸还原酶活性(NRA)。供氮水平降低对细胞间隙CO2浓度(Ci)、蒸腾速率(E)及气孔导度(Gs)没有显著影响,对光合速率(Pn)和水分利用效率(WUEL)的影响则与根区温度有关。常温条件下,1/2N对光合速率的影响具有时段性;低温条件下,1/2N处理光合速率呈高于正常N处理的趋势;高温条件下,1/2N光合速率较低。常温和高温条件下,1/2N处理水分利用效率与正常N处理差异不明显,低温条件下,1/2N处理水分利用效率高于正常N处理。更多还原

【Abstract】 Straw mulching is a widespread farming technique in dryland around world. In China, straw mulching has been used in traditional agriculture long before. Recently, it has been developed quickly in northern China, and becoming an important part in the reduced-tillage and no-tillage system. Growth and development of plant is a systemic process of photosynthesis in leaves with water and nutrition uptake by root system. Soil temperature is one of the important ecological factors and its effects on plant growth and development are not only agriculture and forestry problems but also important theoretical problems. There have been so many contradictions in previous researches. Could straw mulching increase crop yield? Was soil temperature the main cause of yield-reduction of crop under straw mulching? And what was its functional mechanism? No any reasonable answers yet. A field experiment and two water culture experiments were conducted to study the effect of straw mulching on soil temperature and responses of wheat growth to temperature. The main results were obtained as follows:(1)According to the change characteristics of daily mean temperature, the six months from straw mulching to harvest of winter wheat could be divided into 4 stages: Before winter period and Early winter period (Nov.7~Jan.5)——soil temperature decreased quickly, Middle winter period (Jan.6~Jan.25)——soil temperature was the lowest within six months, Late winter period to Turning green stage (Jan.26~Mar.20)——soil temperature raised slowly, Jointing stage to Late stage of winter wheat (Mar.21~May 25)——soil temperature raised continuously. The average soil temperature of 24 hours in a day was significantly higher in mulched soil than no mulch soil. From the period of before winter to turning green stage, the difference of average soil temperature of 24 hours in a day between mulched and no mulch soil was smaller and smaller. The heating effect of straw mulching was significant more and more after turning green stage: temperature at the depth of 10 cm in mulched soil could increase by 2.52℃at the most, and 20 cm was 1.65℃at the most. Maximum of temperature difference at the soil depth of 10 cm between mulched and no mulch soil was at 9:00 to 17:00, and delayed 3~4 hours at the soil depth of 20 cm. The exact time varied with the growing period. Temperature at the soil depth of 10 cm raised from minimum to maximum within 6~9 hours, and there was no significant difference between mulched and no mulch soil. Daily amplitude of soil temperature (Daily Maximum-Daily Minimum) significantly decreased under straw mulching before jointing stage, so the temperature rising and cooling rates were significant lower than no mulch soil. From jointing to late stage of winter wheat, because daily amplitude of soil temperature in mulched soil was significantly higher than no mulch soil, the temperature rising and cooling rates were significantly higher than no mulch soil. The average temperature of 24 hours in a day at the soil depth of 20 cm was significantly higher than 10 cm before winter period to turning green stage, and straw mulching has no significant effect on it. From jointing to late stage of winter wheat, the average soil temperature of 24 hours in a day at the soil depth of 20 cm was lower than 10 cm, and the difference between them in mulched soil significantly higher than no mulch soil. Time of maximum and minimum temperature of mulched soil was in concordance with no mulch soil.(2)Compared with normal temperature treatment, low and high temperature treatments both affected growth and nutrition uptake of winter wheat to a certain degree before winter period to turning green stage. Low temperature had no significant effect on root length of winter wheat before winter period, but it reduced root length during winter period and turning green stage. High temperature increased root length before winter period and over winter period, but it was not favorable to the increase of root length during turning green stage. Compared with normal temperature, low temperature inhibited wheat growth, and the effect on shoot was greater than root before winter period. High temperature before winter period promoted root growth and went against dry matter accumulation in the shoot. During winter period, low temperature was not favorable to the growth of root and shoot. High temperature significantly increased root volume but had no significant effect on shoot growth during winter period. Low temperature significantly inhibited wheat growth during turning green stage, and the effect on root was a little greater than shoot. High temperature mainly affected root growth during turning green stage. Low temperature significantly inhibited nutrient uptake of winter wheat during 3 growing period, and high temperature was also not favorable to the nutrition uptake to a certain degree over winter period. But there was an increasing trend in above ground nutrition uptake at high temperature during turning green stage.(3)Over winter period, root length at 1/2 level of N (6 mmol·L-1) was higher than normal level (12 mmol·L-1) at normal temperature, and the difference between them was little at low temperature. At high temperature, root length at 6 mmol·L-1 was a little lower than 12 mmol·L-1. In this water culture experiment, N supply had no great effect on root and shoot growth of winter wheat. At 6 mmol·L-1, low temperature decreased root dry weight, root volume and shoot dry weight, and high temperature promoted root and shoot growth of winter wheat. N supply decreased had no significant effect on nutrition uptake of winter wheat at normal temperature. 6 mmol·L-1 or 12 mmol·L-1, low temperature significantly decreased nutrition uptake and high temperature significantly increased it. 6 mmol·L-1 or 12 mmol·L-1, high temperature significantly increased nitrate reductase activity (NRA). N supply decreased had no significant effect on CO2 concentration in cell clearance (Ci), transpiration rate (E) and stomatal conductance (Gs), and effects of it on photosynthesis rate (Pn) and water use efficiency at leaf level (WUEL) were related to root zone temperature. The effect at 6 mmol·L-1 on Pn had a given period of time at normal temperature. Pn at 6 mmol·L-1 was higher than 12 mmol·L-1 at low temperature and lower than 12 mmol·L-1 at high temperature. At normal and high temperature, there was no significant difference of WUEL between 6 and 12 mmol·L-1. WUEL at 6 mmol·L-1 was higher than 12 mmol·L-1 at low temperature.更多还原