Abstract

The effect of soil texture on water use efficiency (WUE) was analyzed for six crops cultivated on loam and clay soils. Results were obtained after a long-term study, carried out in a lysimetric set-up, in conditions of experimental neutrality (climate, agro-techniques, and variety were the same for each crop) with the sole exception of the soil texture, which was the variable to be studied.

In the case of potato, corn, sunflower, and sugar beet, WUE was reduced significantly when crops were grown in clay soil. The reductions ranged from 22% to 25%. The decrease of WUE in clay soil was coupled with significant reductions in yield and in ET, except in the case of the corn crop. The reduction in WUE in corn depended solely on the yield decrease.

A 10% decrease in WUE values was also observed for the soy-bean and tomato grown in clay soil, but it was not statistically significant.

Different causes which may reduce the WUE values observed in the clay soil are discussed. It seems coherent to hypothesize that, during the active growing phase, a deficit in water uptake occurs in the plants growing in the clay soil. This hypothesis is consistent with the observations of stomatal conductance, daily evapotranspiration, and leaf surface.

In conclusion, the operative development of this study is outlined.

Corn was planted in containers with a volume of 3 m × 2 m × 1 m , in which different textural soils including light loam, loam and light clay were filled as the natural status. The effect of soil textural on corn root was studied. The results showed that the morphology, distribution, growth of corn root system were significantly different among three kinds textural soils. Corn root in light clay changed direction frequently during growth process so that it had more curved root system compared with that in light loam and loam, which characterized by "more deeper in light clay soil, more finer root diameter". More sub-roots in basal and less sub-roots in deeper soil were also observed in light loam than that in loam and light clay soil. The sequence of average root diameter(ARD) was light clay＞loam＞light loam. At jointing stage, the vertical and horizontal distribution of corn root cultivated in light loam was the most extensive, followed by loam and light clay. However, no significant difference was found among three kinds textural soils after male tetrad stage. The portion of root in top soil increased with more physical light clay component in soil. Growth dynamic of corn root in light loam was characterized by "earlier development and earlier senescence". Daily increase rate of root length density in light loam was far higher than that in loam and light clay, which reached 538.6 m·m-3·d-1 before jointing stage and root amount reached maximum at silking stage, then root began senescent. Growth dynamic of corn root in light clay was characterized by "later development and later senescence", that daily increase rate of root was low in early stage, root amount reached maximum at doughy stage and senesce rate was far lower than that of light loam during late stage. Root in loam had a balanced growth during the whole period.

Corn was planted in containers with a volume of 3 m × 2 m × 1 m , in which different textural soils including light loam, loam and light clay were filled as the natural status. The effect of soil textural on corn root was studied. The results showed that the morphology, distribution, growth of corn root system were significantly different among three kinds textural soils. Corn root in light clay changed direction frequently during growth process so that it had more curved root system compared with that in light loam and loam, which characterized by "more deeper in light clay soil, more finer root diameter". More sub-roots in basal and less sub-roots in deeper soil were also observed in light loam than that in loam and light clay soil. The sequence of average root diameter(ARD) was light clay＞loam＞light loam. At jointing stage, the vertical and horizontal distribution of corn root cultivated in light loam was the most extensive, followed by loam and light clay. However, no significant difference was found among three kinds textural soils after male tetrad stage. The portion of root in top soil increased with more physical light clay component in soil. Growth dynamic of corn root in light loam was characterized by "earlier development and earlier senescence". Daily increase rate of root length density in light loam was far higher than that in loam and light clay, which reached 538.6 m·m-3·d-1 before jointing stage and root amount reached maximum at silking stage, then root began senescent. Growth dynamic of corn root in light clay was characterized by "later development and later senescence", that daily increase rate of root was low in early stage, root amount reached maximum at doughy stage and senesce rate was far lower than that of light loam during late stage. Root in loam had a balanced growth during the whole period.

An investigation was made on the yield component, dry matter allocation, root distribution in 0-100 cm soil layer, and soil physical and chemical properties in two high yielding (>19500 kg·hm^-2) spring maize fields of Yulin, Shaanxi Province. In the two fields, the planting density was from 105000 plants·hm^-2 to 123000 plants·hm^-2, spike rate was from 97.7% to 102.2%, 1000-grain weight was >320 g, and the dry matter allocation in ears occupied 60.2%-65.5% of the total. The average bulk density in 0-100 cm soil layer was from 1.28 g·cm^-3 to 1.33 g·cm^-3, and the soil bulk density, porosity, and field water-holding capacity along the profile all changed in M type. Maize roots were mainly distributed in 0-60 cm soil layer, and those in 0-20 cm and 20-60 cm accounted for 64.8%-72.1% and 23.30%-28.17% of the total, respectively. There was a close relationship between root distribution and soil physical-chemical properties. Root dry mass in 0-20 cm soil layer had a significant positive correlation with soil organic matter, total nitrogen, and total phosphorus, while that in 20-60 cm soil layer was significantly correlated with soil bulk density and field water-holding capacity. Therefore, to select soils with good permeability and high maintenance capacity of water and nutrients would be the key in obtaining high maize yield.

An investigation was made on the yield component, dry matter allocation, root distribution in 0-100 cm soil layer, and soil physical and chemical properties in two high yielding (>19500 kg·hm^-2) spring maize fields of Yulin, Shaanxi Province. In the two fields, the planting density was from 105000 plants·hm^-2 to 123000 plants·hm^-2, spike rate was from 97.7% to 102.2%, 1000-grain weight was >320 g, and the dry matter allocation in ears occupied 60.2%-65.5% of the total. The average bulk density in 0-100 cm soil layer was from 1.28 g·cm^-3 to 1.33 g·cm^-3, and the soil bulk density, porosity, and field water-holding capacity along the profile all changed in M type. Maize roots were mainly distributed in 0-60 cm soil layer, and those in 0-20 cm and 20-60 cm accounted for 64.8%-72.1% and 23.30%-28.17% of the total, respectively. There was a close relationship between root distribution and soil physical-chemical properties. Root dry mass in 0-20 cm soil layer had a significant positive correlation with soil organic matter, total nitrogen, and total phosphorus, while that in 20-60 cm soil layer was significantly correlated with soil bulk density and field water-holding capacity. Therefore, to select soils with good permeability and high maintenance capacity of water and nutrients would be the key in obtaining high maize yield.

The experiments with different densities and fertilizer levels were carried out on corn hybrid SuYu9 to investigate the activity of root system relating to dry matter accumulation and grain yield. The results showed that there were positive correlations between brace root number and total root numbe

The experiments with different densities and fertilizer levels were carried out on corn hybrid SuYu9 to investigate the activity of root system relating to dry matter accumulation and grain yield. The results showed that there were positive correlations between brace root number and total root numbe

Dry weight of tobacco root on different types of soil had the same growth tendency increasing slowly before topping, increasing quickly 10 days after topping and decreasing rapidly there after.Root dry weight on Cinnamon soil increased most quickly in early period and slowly during middle period, and also decreased slowly in later period, so it changed comparatively peacefully; on Shajiang black soil, it increased most slowly in early period, and fastest during middle period, and decreased most rapidly in later period. On Alluvial soil, it changed in the between. During the maximum root dry weight stage, dry weight of tobacco root in different types of soil were:Shajiang black soil > Alluvial soil > Cinnamon soil. Tobacco root length in different types of soil extended in the same tendency extending slowly before June 10th, quickly from June 10th to July 18th, and keeping extending slowly after wards. On July 18th the root length of different types of soil were:Cinnamon soil > Shajiang black soil > Alluvial soil. Tobacco root weight, length, total surface area and active absorption area had the same vertical distribution the values of different arable layers were:0~20cm > 20~40cm > 40~60cm > 60~80cm. The characteristics of vertical distribution of root dry weight on different types of soil were that RDW on Shajiang black soil was shallow and intensive, and on Cinnamon soil was deep and extensive, and on Alluvial soil was in the between. The characteristics of root length vertical distribution were that root length of Shajiang black soil distributed shallow and intensive, and that of Cinnamon soil deeply and extensively, and Alluvial soil in the mediate degree. As to the characteristics of root total surface area and active absorption area vertical distribution, Alluvial soil distributed shallow and intensively, Cinnamon soil deeply and extensively, and the Shajiang black soil in mediate degree; furthermore, the root surface area and active absorption area of different types of soil were:Shajinag black soil > Alluvial soil > Cinnamon soil. Root weight and length of Shajiang black soil distributed most narrowly, and of Cinnamon soil and Alluvial soil most widely.

Dry weight of tobacco root on different types of soil had the same growth tendency increasing slowly before topping, increasing quickly 10 days after topping and decreasing rapidly there after.Root dry weight on Cinnamon soil increased most quickly in early period and slowly during middle period, and also decreased slowly in later period, so it changed comparatively peacefully; on Shajiang black soil, it increased most slowly in early period, and fastest during middle period, and decreased most rapidly in later period. On Alluvial soil, it changed in the between. During the maximum root dry weight stage, dry weight of tobacco root in different types of soil were:Shajiang black soil > Alluvial soil > Cinnamon soil. Tobacco root length in different types of soil extended in the same tendency extending slowly before June 10th, quickly from June 10th to July 18th, and keeping extending slowly after wards. On July 18th the root length of different types of soil were:Cinnamon soil > Shajiang black soil > Alluvial soil. Tobacco root weight, length, total surface area and active absorption area had the same vertical distribution the values of different arable layers were:0~20cm > 20~40cm > 40~60cm > 60~80cm. The characteristics of vertical distribution of root dry weight on different types of soil were that RDW on Shajiang black soil was shallow and intensive, and on Cinnamon soil was deep and extensive, and on Alluvial soil was in the between. The characteristics of root length vertical distribution were that root length of Shajiang black soil distributed shallow and intensive, and that of Cinnamon soil deeply and extensively, and Alluvial soil in the mediate degree. As to the characteristics of root total surface area and active absorption area vertical distribution, Alluvial soil distributed shallow and intensively, Cinnamon soil deeply and extensively, and the Shajiang black soil in mediate degree; furthermore, the root surface area and active absorption area of different types of soil were:Shajinag black soil > Alluvial soil > Cinnamon soil. Root weight and length of Shajiang black soil distributed most narrowly, and of Cinnamon soil and Alluvial soil most widely.

Soil texture is an important factor to effect the toxicity of heavy metal on crop plants. In order to investigate the effects of three textures of soil including loam soil, clay soil and sandy soil on the photosynthetic characteristics of wheat flag leaves under chromium stress, traits of morphology and photosynthesis of wheat, such as plant biomass, length and numbers of root, photosynthetic rate(Pn), stomata conductance(Gs), intercellular CO₂ concentration(Ci), transpiration rate(Tr), water utilization efficiency(WUE), and relative content of chlorophyll were studied during grain-filling stage. The results showed that, with the increasing of chromium concentration, the length of root decreased in clay soil, while it was shown as the trend of increasing first and then decreasing in loam soil and sandy soil, which reaching the peak at the chromium concentration of 100 mg·kg^-1. In three soil textures,lateral root numbers were all reduced as the chromium concentrations increasing; biomass of different organs were decreased also; the Pn decreased in loam soil and showed the trend of increasing first and then decreasing in clay soil and sandy soil, which reached the peak as chromium concentrations was 100 and 200 mg·kg^-1, respectively; the Gs, Ci, Tr and relative content of chlorophyll of flag leaves showed a trend of increasing first and then decreasing, and to their peak at the chromium concentration of 100 mg·kg^-1 in loam soil and clay soil, and at 200 mg·kg^-1 in sandy soil; the WUE increased at first and then decreased in clay soil, showing rising trend in sandy soil and little fluctuation in loam soil. To sum up, there were distinct inhibitions or increasing first and then decreasing trends of photosynthetic indexes of wheat flag leaves during grain-filling stage with chromium stress. While chromium concentration was more than 200 mg·kg^-1, theses stress effects on wheat were showed more and more obviously, such as reduction of root length and root number, decrease of Gs, Ci, Tr and relative content of chlorophyll of flag leaves, as well as the biomass of different organs. Additionally, in the three soil textures, photosynthesis indexes of the flag leaves of wheat during grain-filling stage declined in different degrees with chromium stress, but these decreasing trends were more obvious in sandy soil than that in loam soil and clay soil.

Soil texture is an important factor to effect the toxicity of heavy metal on crop plants. In order to investigate the effects of three textures of soil including loam soil, clay soil and sandy soil on the photosynthetic characteristics of wheat flag leaves under chromium stress, traits of morphology and photosynthesis of wheat, such as plant biomass, length and numbers of root, photosynthetic rate(Pn), stomata conductance(Gs), intercellular CO₂ concentration(Ci), transpiration rate(Tr), water utilization efficiency(WUE), and relative content of chlorophyll were studied during grain-filling stage. The results showed that, with the increasing of chromium concentration, the length of root decreased in clay soil, while it was shown as the trend of increasing first and then decreasing in loam soil and sandy soil, which reaching the peak at the chromium concentration of 100 mg·kg^-1. In three soil textures,lateral root numbers were all reduced as the chromium concentrations increasing; biomass of different organs were decreased also; the Pn decreased in loam soil and showed the trend of increasing first and then decreasing in clay soil and sandy soil, which reached the peak as chromium concentrations was 100 and 200 mg·kg^-1, respectively; the Gs, Ci, Tr and relative content of chlorophyll of flag leaves showed a trend of increasing first and then decreasing, and to their peak at the chromium concentration of 100 mg·kg^-1 in loam soil and clay soil, and at 200 mg·kg^-1 in sandy soil; the WUE increased at first and then decreased in clay soil, showing rising trend in sandy soil and little fluctuation in loam soil. To sum up, there were distinct inhibitions or increasing first and then decreasing trends of photosynthetic indexes of wheat flag leaves during grain-filling stage with chromium stress. While chromium concentration was more than 200 mg·kg^-1, theses stress effects on wheat were showed more and more obviously, such as reduction of root length and root number, decrease of Gs, Ci, Tr and relative content of chlorophyll of flag leaves, as well as the biomass of different organs. Additionally, in the three soil textures, photosynthesis indexes of the flag leaves of wheat during grain-filling stage declined in different degrees with chromium stress, but these decreasing trends were more obvious in sandy soil than that in loam soil and clay soil.