Response Of Wheat And Corn Under Soil Compaction Induced By Tractor Traffic

Soil compaction occurs when soil particles are pressed together, thus reducing pore spaces between them. Compaction is caused by the use of heavy machinery, pressure from wheels, tillage equipment, trampling by animals, reduced use of organic matter, frequent use of chemical fertilizers and plowing at the same depth for many years. The signs of soil compaction can often be seen by observing the crops growing in a compacted soil. Slow plant emergence, thin stands, uneven early growth, small grain heads, abnormal rooting patterns and reduced nutrients uptake can be a reflection of compaction. Excessive soil compaction impedes root growth and therefore limits the amount of soil explored by roots. Soil compaction is problem of global concern and very few have worked on this issue in China. Therefore this research work was conducted to investigate and document the deleterious effects of soil compaction on crop and soil properties, as well as to evaluate best and cheap improvement measures for reducing subsurface soil compaction.Two field experiments were conducted during the year 2005-06 and repeated during the year 2006-07 at the Jiangpu Farm of Nanjing Agricultural University, Jiangsu Province of China. In first experiment the effects of soil compaction were studied. In second experiment the effects of improvement measures applied to the artificially compacted subsurface soil were investigated, in first experiment, the soil was compacted with one pass of holder tractor, wheel tractor and crawler in T1, two passes of holder tractor, wheel tractor and crawler in T2, four passes of holder tractor, wheel tractor and crawler in T3, while no compaction was applied in T4 (control). The number of passes of tractors measured at the level of compaction. The experiment consisted of four treatments. The topsoil at 5 cm was re-tilled with a rotary plow and wheat variety Nanjing-601 and corn variety Baiyu-109 was grown.In second experiment different improvement measures were applied to subplots according to sowing plan. The experiment consisted of five strategies, S1 received deep plowing (D.P.), S2 received D.P.+FYM at 10000 kg/ha, S3 received D. P.+Gypsum at 2000 kg/ha, S4 received D.P+F’YM+Gypsum at the rates mentioned above while in S5 (control) no addition of improvement measure was made. The subsurface of the whole plot was compacted with 4 passes of a holder tractor, two wheel drive tractor and crawler tractor. Lay out was carried out and deep plowing was given to all the sub plots at a depth of 15 cm. Wheat variety Nanjing-601 was grown in all the plots with a seeding rate of 236 kg/ha.In first experiment compaction significantly affected soil strength, subsurface bulk density, subsurface soil porosity, days to an thesis, days to maturity, plant height, spikes per square meter, grains per spike, thousand grain weight, biological yield, grain yield, harvest index, crop growth rate (CGR), root length, percent grain protein, N concentration in plants (%). P concentration in plants (%) and K concentration in plants (%), while non significant variations were observed for days to emergence, emergence per square meter, tillers per square meter, upper surface bulk density and upper surface soil porosity, total soil nitrogen, available soil phosphorus and available soil potassium among different treatment means averaged over the years. The maximum values of above parameters were recorded for T4 (control) and the minimum for T3 except subsurface soil bulk density where the maximum values were recorded for T3 and minimum for T4 (control). Almost all parameters showed a decreasing trend with increasing the level of soil compaction. Interactive effects varied inconsistently. Significant effects on different parameters may be attributed to changed physical conditions of the soil due to compaction which ultimately affected growth and development parameters. However, slightly higher values were observed during second year of experiment as compared to first year which may be the effect of overall climatic conditions as during second year more rains were received. Average maximum and average minimum temperature was noticed to be lower than that recorded during first year which thus increased the total length of crop life cycle.In second experiment, addition of improvement measures to the artificially compacted subsurface soil significantly affected days to anthesis, days to maturity, plant height, tillers per square meter, Spikes per square meter, grains per spike, thousand grain weight, biological yield, grain yield, harvest index, root length, crop growth rate, percent grain protein, subsurface soil resistance, subsurface shear stress, subsurface bulk density, subsurface soil porosity, N concentration (%) in plants, P concentration (%), K concentration (%). soil N (%), soil P (%) and soil K (%) during the years of study, Non significant variations were observed among days to emergence, emergence per square meter, upper surface soil resistance, upper surface bulk density and upper surface soil porosity during the years of study. The maximum values of these parameters were recorded for S4 (D.P.+FYM+Gypsum) followed by S2 (D.P.+FYM). While minimum values were recorded for S5 (control), except subsurface soil bulk density where minimum values were recorded for S4 and S2 and maximum for S5 (control). The maximum values recorded for treatments where deep plowing+farm yard manure was added may be attributed that these amendments left positive effects on overall soil structure thus giving positive response. So, where soil compaction hinders in good crop production these amendments may ameliorate the negative effects. Interactive effects varied inconsistently. However, slightly higher values were observed during second year of experiment as compared to first year.