[Temporal and spatial variation of water requirement of winter wheat and its influencing factors in Henan Province, China].

Based on mean meteorological data of ten days in 17 observation stations from 1961 to 2012, the reference crop evapotranspiration was computed using Penman-Monteith formula recommended by FAO. The water requirement of winter wheat in Henan Province was calculated by adopting crop coefficients and the growth stage of winter wheat from the "National Irrigation Experiment Database", and the temporal and spatial distribution, variation and affecting factors in recent 51 years were analyzed by means of time-series analysis and gray relational grade analysis. The results showed that the average water requirement of winter wheat was 345-492 mm in Henan Province from 1961 to 2011, and it was lowest at Lushi station and highest at Mengjin station. The average water requirement of winter wheat was lowest from 1980 to 1989 and highest from 1961 to 1969 at most stations. The water requirement of winter wheat showed a tendency to increase with years at the 7 stations (Xinxiang, Luanchuan, Kaifeng, Xixia, Nanyang, Xinyang and Gushi) , while it indicated a tendency to decline in the other 10 stations. The water requirement of winter wheat in North Henan was higher than in South Henan, and had a high span variation in West Henan. During the growing period of winter wheat, the average daily maximum and minimum temperatures showed a tendency to increase with years, while the average daily wind speed and relative humidity, and the sunshine hours had a tendency to decline. In Henan Province, the water requirement of winter wheat was mainly affected by the average daily maximum temperature and the sunshine hours, and least influenced by the average daily relative humidity.

[Effects of girdling on growth, yield and water use efficiency of cotton].

An experiment with girdling applied on the main stem and fruit branch during the early or flourishing stage of flowering and boll-setting was conducted to investigate the effects of different girdling treatments on the growth, yield and water use efficiency (WUE) of cotton. The results showed that compared with the control (CK), leaf area index (LAI) of girdling treatments reduced significantly and the maximum LAI of girdled cotton occurred 5-15 days in advance. Girdling reduced the shedding rate of squares and bolls significantly, and the shedding rate of squares and bolls with girdling applied on the main stem at the flourishing stage was 15.8% lower than that of CK. In contrast with CK, the seed-cotton yield and WUE increased by 24.4% and 26.7% with girdling applied on the main stem at the flourishing stage, and increased by 13.9% and 16.7% with girdling applied on the fruit branch at the early stage, respectively. However, the girdling on the fruit branch at the flourishing stage improved the seed-cotton yield and WUE insignificantly. The seed-cotton yield with girdling on the main stem at the early stage had not significant difference and its WUE reduced slightly compared with CK. It has been concluded that the girdling applied on the main stem at the flourishing stage of flowering and boll-setting could effectively reduce the abscission rate of squares and bolls, improve yield and WUE significantly, and realize the effective unity of high production and water-saving.

[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.