[Effects of nitrogen and irrigation water application on yield, water and nitrogen utilization and soil nitrate nitrogen accumulation in summer cotton]. / 水氮供应对夏棉产量、水氮利用及土壤硝态氮累积的影响.

A field experiment was carried out to study the effects of nitrogen and irrigation water application on growth, yield, and water and nitrogen use efficiency of summer cotton, and to develop the optimal water and nitrogen management model for suitable yield and less nitrogen loss in summer cotton field in the Huang-Huai region. Two experimental factors were arranged in a split plot design. The main plots were used for arranging nitrogen factor which consisted of five nitrogen fertilizer le-vels(0, 60, 120, 180, 240 kg·hm-2, referred as N0, N1, N2, N3, N4), and the subplots for irrigation factor which consisted of three irrigation quota levels (30, 22.5, 15 mm, referred as I1, I2, I3). There were 15 treatments with three replications. Water was applied with drip irrigation system. Experimental results showed that both irrigation and nitrogen fertilization promoted cotton growth and yield obviously, but nitrogen fertilizer showed more important effects than irrigation and was the main factor of regulating growth and yield of summer cotton in the experimental region. With the increase of nitrogen fertilization rate and irrigation amount, the dry mater accumulation of reproductive organs, the above-ground biomass at the flowering-bolling stage and seed cotton yield increased gradually, reached peak values at nitrogen fertilization rate of 180 kg·hm-2 and decreased slowly with the nitrogen fertilization rate further increased. The maximum yield of 4016 kg·hm-2 was observed in the treatment of N3I1. Increasing nitrogen fertilizer amount would improve significantly total N absorption of shoots and N content of stem and leaf, but decrease nitrogen partial factor productivity. The maximum irrigation-water use efficiency of 5.40 kg·m-3 and field water use efficiency of 1.24 kg·m-3 were found in the treatments of N3I3 and N3I1, respectively. With increasing nitrogen fertilization amount, soil NO3--N content increased and the main soil NO3--N accumulation layer moved downward. By comprehensively considering above-ground biomass, seed cotton yield, water and nitrogen uptake and utilization, and soil NO3--N accumulation in the soil profile, the treatment N3I1 could be recommended as the optimal water and nitrogen application pattern for summer cotton production in the experimental region.

[Differences in root developmenly of winter wheat cultivars in Huang-Huai Plain, China].

Selecting one presently popularized winter wheat cultivar (Zhengmai 9023) and two cultivars (Abo and Fengchan 3) introduced in the 1950s and 1960s in Huang-Huai Plain as test materials, and by using minirhizotron technique, this paper studied the live root length, root diameter distribution, and net root growth rate of the cultivars. Fine roots with a diameter from 0.05 mm to 0.25 mm occupied the majority of the whole root system, and the fine roots with a diameter less than 0.5 mm accounted for 98% of the live root length. The average root diameter varied with plant growth, the variation range being 0.15 - 0.22 mm, and no significant difference was observe among the cultivars. The live root length was significantly positively correlated root number, suggesting that root number was the main factor for the increase of live root length. The most vigorous growth period of the roots was from reviving to jointing stage, and Abo and Fengchan 3 had a longer period increased root vitality, as compared with Zhengmai 9023. For Zhengmai 9023, its fine roots with a diameter more than 0.1 mm had an increasing proportion after jointing stage, which was helpful for improving plant resistance, root activity, and grain-filling at late growth stages.

[Estimation model for water requirement of greenhouse tomato under drip irrigation].

Based on the modified Penman-Monteith equation, and through the analysis of the relationships between crop coefficient and cumulative temperature, a new model for estimating the water requirement of greenhouse tomato under drip irrigation was built. The model was validated with the measured data of plant transpiration and soil evaporation in May 2-13 (flowering-fruit-developing stage) and June 9-20 (fruit-maturing stage) , 2009. This model was suitable for the estimation of reference evapotranspiration (ET(0)) in greenhouse. The crop coefficient of greenhouse tomato was correlated as a quadratic function of cumulative temperature. The mean relative error between measured and estimated values was less than 10%, being able to estimate the water requirement of greenhouse tomato under drip irrigation.

[Plant transpiration in a maize/soybean intercropping system measured with heat balance method].

In an experimental field with maize/soybean strip intercropping, the transpiration of maize and soybean plants was measured with sap flow gauge based on heat balance method. In the intercropping system, the diurnal change of the sap flow rates of the plants fitted single-peak curve in sunny day and multi-peak curve in cloudy day. The plant sap flow rates were affected by many environmental factors, among which, solar radiation was the most important meteorological factor. The daily sap flow per maize or soybean plant showed significant correlations with solar radiation, air temperature, relative humidity, wind speed, and soil heat flux. During the observation period (June 1-30, 2008), the mean daily transpiration of maize plant (1.44 mm x d(-1)) was about 1.8 times of that of soybean plant (0.79 mm x d(-1)). Maize transpiration and soybean transpiration contributed 64% and 36% to the total transpiration of the intercropping system, respectively. Due to the spatial variation of stem diameter and leaf area, it would be necessary to install more sap flow gauges to accurately measure the sap flow of maize and soybean plants.

[Crop root growth and water uptake in maize/soybean strip intercropping].

A field experiment was conducted to study the root distribution and water adsorption of maize and soybean in their strip intercropping. The results showed that under the condition of full irrigation, both maize roots and soybean roots were distributed approximately in triangle-shape in soil profile. Maize roots extended horizontally into a wider area, 58 cm away from the plant row and usually occurred in 16-22 cm soil layer. They were not restricted to maize root zone, but traversed into soybean strip zone. Soybean roots were horizontally distributed in a limited zone near the plant row, and their reached range was within about 26 cm. Both for maize and for soybean, their root mass density decreased with increasing distance from the plant row. About 90% of the root mass of maize and edge-row soybean was presented in 0-30 cm soil layer. The root mass density of maize at 10 cm from maize row was greater than that of soybean, but this density of soybean at 20 cm from maize strip was greater than that of maize. About 85% of root mass was distributed in 0-30 cm soil layer, and the variation of soil water content in intercropping strips also occurred mainly in this soil layer. In the maize/soybean strip intercropping system, soil water content decreased in the order of maize zone > soybean zone > middle zone, indicating that each strip-intercropped crop preferentially absorbed the soil water in its strip and utilized the soil water in intermingled zone later.

[Effects of soil moisture regime on greenhouse tomato yield and its formation under drip irrigation].

Field plot experiment was conducted to study the effects of soil moisture regime at different growth stages on the fruit size, fruit number, percentage of malformed fruit, and yield formation of greenhouse tomato under drip irrigation, and the relationships between tomato yield and irrigation amount. Moderate soil water deficit (50%-55% of field capacity) at tomato's seedling stage increased the fruit number but reduced the fruit size, decreased the percentage of malformed fruit, and made the fruit maturation mainly concentrated in later picking period. Severe water deficit (less than 65% of field capacity) at flowering and fruit-developing stages promoted fruit maturation, but decreased fruit number and increased the formation of small and malformed fruits. The soil moisture content higher than 80% or lower than 65% of filed capacity at fruit maturation stage less affected fruit maturation but decreased fruit yield, and lower than 65% of filed capacity also decreased the fruit number and increased the percentage of malformed fruit. No significant effects of irrigation amount on fruit maturation were observed. The correlations of tomato yield and its water use efficiency with irrigation amount could be well described by quadratic function. The fruit number and total yield were higher while the percentage of malformed fruit was lower when the soil moisture content was controlled at 60%-65% of field capacity at seedling stage, 70%-75% of field capacity at flowering stage, and 70%-75% of field capacity at fruit-developing stage, which could be used as the optimal soil moisture indices for the greenhouse tomato production under drip irrigation.

[Light environment characteristics in maize-soybean strip intercropping system].

Observations on the light environment characteristics in maize-soybean narrow stnp intercropping system were made in 2006 and 2007 to study the spatial distribution of photosynthetically active radiation (PAR) in intercropped crop canopy, and to analyze the effects of light environment on crop biomass. The results indicated that in early growth period, the light transmittance at the bottom of the edge rows of soybean strips adjacent to maize was higher than that of the inner rows of soybean strips, while it was in adverse for maize strips. The horizontal variation of light transmittance at the bottom of crop canopy did not vary significantly at reproductive stage, and the average light transmittance was less than 7%. In soybean strips, the daily photosynthetic photon flux density (PPFD) above inner rows canopy in early growth period was 10% higher than that above edge rows canopy, and the average light transmittance of edge rows and inner rows in 1: 3 intercropping system (treatment I1) was about 15% higher than that in 2:3 system (treatment I2), indicating that the shading of maize strips on soybean strips was more senous in treatment I2 than in treatment I1. After flowering, there was a significant difference in the daily PPFD between inner rows and edge rows of soybean strips, but no significant difference was observed between edge rows. The mean light transmittance of edge rows and inner rows of soybean strips was 27% and 38%, respectively, and there was no significant difference between treatment I1 and treatment I2, which indicated that the shading effects of maize strips on soybean strips in treatment I1 and treatment I2 were similar at reproductive stage. The biomass of inner rows of soybean strips was larger than that of edge rows, and there was no significant different between edge rows, indicating that under adequate irrigation, the effects of different narrow strip intercropping systems on crop biomass were primarily due to the changes of light environment.

[Spatiotemporal distribution patterns of winter wheat and spring maize root systems under intercropping].

In this paper, root samples of winter wheat and spring maize under intercropping were taken with large-bore soil auger, and the dynamics of their spatiotemporal distribution were studied. The results showed that both in vertical and in horizontal directions, the root mass of winter wheat decreased in power function, while that of spring maize decreased in exponent function. Multiple linear regression was made to establish the two-dimensional spatiotemporal distribution functions of intercropped winter wheat and spring maize root biomass, and the validation tests demonstrated that theses functions were available to describe the real growth status of test crops root systems.