Effects Of Soil Compaction On Root-soil System And Development In Maize

Improving grain yield of maize and soil productivity is now one of the key subjects.Soil compaction is a main constraint to root and shoot growth, it is the main physical stress that limits crop growth and yield.The studies on the effect of the soil compaction stress on the maize Eco-physiology and regulate measures were carried out at three locations, Henan Agricultural University Experomental Station with the methods of pot and barrel research combined with field research on three soil types during 2007-2009,repectively.Effects were studied of soil compaction stress on the growth and distribution of root, root microstructure, root respiratory metabolism, root endogenous hormones, nutrient absorbing and distribution, soil microbial biomass carbon and nitrogen , soil respiration and corn growth and yield. The results were as follows:;1,A barrel expriment were conducted to research root morphology and physiological characteristics in three soil types(fluvo-aquic soil, lime concretion black soil and yellow cinnamon soil) under soil compaction stress.The results showed that root length, root dry weight ,individual root, total root surface area,root volume were decreased significantly under soil compaction stress in different soil types, while that of root diameter exhibited the opposite. In addition, root total absorbing area, root activitily absorbing area, root activities , root ATPase activity and root/shoot ratio declined prominently. Ratio of absorbing area and ratio of activitily absorbing area to root weight were increased distinctly. The order of all parameters was fluvo-aquic soil > lime concretion black soil > yellow cinnamon soil, but three soil types varied different trend responding to soil compaction stress, Among them lime concretion black soil and yellow cinnamon soil were influenced largely and sensitivily, while fluvo-aquic soil was influenced slightly by soil compaction stress. During the growth of maize, some parameters were single peak curves, The highest values appeared at the silking stage.2,In the pot experiments stated ablove,studies were carried out to evaluate the effects of soil compaction stress on root morphology, root respiratory metabolism, root endogenous hormones and root protective enzyme activity under three soil types. The results showed that there were much more aerenchyma formation under soil compaction stress. Aerenchyma number and aerenchyma area on the root transection were increased significantly under high soil compaction. Length of cortex and diameter of plerome were also enhanced largely, and number and diameter of vessel were increased to some cxtent. Radial and transverse length of cortical cells discreased under soil compaction stress.The diversity of them were extremely significant between high soil compaction and normal soil compaction. There were different orders among three soil types. Lime concretion black soil and yellow cinnamon soil were influenced largely and sensitivily among them.The activities of pyruvate decarboxylase(PDC), lactate dehydrogenase(LDH) and alcohol dehydrogenase(ADH) increased significantly under soil compaction stress.The contents of lactat, acetaldehyde and alcoho also were increased evidently under high soil compaction.but increment of these indexes was lesser than that of these under water-logging treatment.The contents of indoleacetic acid (IAA),gibberellins (GA) and zeatin riboside (ZR) in root decreased under high soil compaction,while abscisic acid content in root increased. The value of IAA/ABA,GA/ABA,ZR/ABA were lower under high soil compaction than normal compaction.while the value of IAA/ZR was higher under high soil compaction. Under soil high compaction activities of superoxide dismutase (SOD) and peroxidase (POD) decreaesed to some extent, but content of (MDA)was enhanced significantly.3,Under high soil compaction the order of nutrient accumulation was N>K>P in different soil types, and the order of total accumulation of N, P, K in per corn was fluvo-aquic soil>lime concretion black soil>yellow cinnamon soil. Statistical analysis indicated that there were significant difference among these soil types. The order of nitrogen, phosphorous and potassium consumption in leaves and culm-sheath agreed with that in plant, and the proportion of distribution in leaves was a few higher than that in the culm-sheath. Total accumulation of N, P, K in per corn and distribution of N,P,K in leaf, culm-sheath and grain were enhanced highly with the decreasing of soil compaction.Among three soil tyes the extent of increasing in lime concretion black soil and yellow cinnamon soil were higher than that in fluvo-aquic soil. Besides the transferring rate of N,P,K in leaves and culm-sheath were increased a littler under high soil compaction.In three soil types the order of nitrogen use efficiency was fluvo-aquic soillime concretion black soil>yellow cinnamon soil under soil high compaction. With soil compaction decreasing, SMBC and SMBN were increasing. These were enhanced highly in lime concretion black soil and yellow cinnamon soil and increased less in fluvo-aquic soil.The effect of soil high compaction on SMBN and SMBC were more evident in the 20-40 cm than in the 0-20 cm.The value of MBC/SOC was higher in yellow cinnamon soil than in fluvo-aquic soil and lime concretion black soil,while the value of MBN/TN exhibited opposite. The lower the soil compaction, the more significant the increasing the value of MBC/SOC and MBN/TN.The increase of MBC/SOC was higher in yellow cinnamon soil and fluvo-aquic soil,while the increase of MBN/TN was less in lime concretion black soil.The order of value of soil microbial biomass carbon to soil microbial biomass nitrogen (SMBC/SMBN) was yellow cinnamon soil > lime concretion black soil> fluvo-aquic soil.The value of SMBC/SMBN decreased with the soil compaction decreasing. SMBC and SMBN were positive correlation with soil organic carbon,total nitrogen and available nitrogen. MBC/SOC was extreme correlation with SOC and SMBC.The soil respiration and dinrual changes of its were single curve in different soil types under soil high compaction.The highest values of soil respiration and rhizospheric respiration were at the silking stages and 25th day after silking respectively. The order of respiration changes was fluvo-aquic soil>lime concretion black soil>yellow cinnamon soil.These were some factors of root biomass,organism biomass,total biomass, leaf area index,SMBC,SMBN,soil temperature and soil moisture on soil respiration in turn.5,During the growth of maize, Leaf area index(LAI) and content of soluble sugar were single curves.The value of SPAD decreased from 14th day after silking.The order of changes of LAI,height and diameter of stem,dry matter,content of soluble sugar,value of SPAD and yield was fluvo-aquic soil>lime concretion black soil>yellow cinnamon soil.these diversity were significantly.These parameters increased evidently with soil compaction decreaesing.but 100 kernel weight was affected hardly.With soil compaction decreasing,the difference was reduced significantly.The order of different soil types was not changed.this was also T fluvo-aquic soil>T lime concretion black soil>T yellow cinnamon soil.By deep tillage or deep tillage added ridging,soil compaction and bulk density decreased ,and soil porosity was enhanced extremely significantly.The decreasing of soil bulk density was by 10.41% and 13.97% in the 0-20cm and 20-40cm depth. The increasing of soil porosity was by 17.91% and 30.51%in this two soil layers.The kernel per plant and yield were increasing by 6.8-12.7% and 10.35%-16.71%with soil conmoaction decreasing.