RADIATION REGIME OVER ROW ORIENTATION IN WINTER WHEAT (Triticum aestivum L.)
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Date
2004
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AAU, Anand
Abstract
A field experiment was conducted during the rabi season of 2003-2004 at Anand. The experiment was laid out in Split Plot Design with the two dates of sowing as main plot and four treatment combinations of two row orientation and two row spacing as sub-plots, replicated four times. The objective was to study solar radiation regime with respect to the row orientation, row spacing and leaf geometrical parameters for Wheat crop (cv. GW- 496). The experiment was planned with the objectives to determine the influence of the treatments on the RUE, Extinction Coefficient (k), Direct beam radiation interception, soil surface temperature and soil moisture lost/evapotranspiration (as influenced by radiation penetration between rows). Comparison of the season encountered by the crop during the experimental period with that normally found in the region was made by comparing the seasonal values of different weather parameters with their normal for Anand. The nonsignificant differences in respect of each of the weather parameters established that the experimental season was identical to the normal one. Hence these results could be applicable to any normal wheat growing season around Anand region. The experimental findings obtained during the course of the present investigation revealed that the highest interception was recorded during the morning hours and there was negligible difference among the treatments in this respect. The difference in the interception was higher during noon time and narrow NS rows intercepted higher PAR (0.92). Wide NS rows and wide EW rows had higher solar radiation interception than that narrow EW rows at noon hours. The seasonal average of the fraction F indicated more or less identical results that representing different treatments, narrow NS oriented row had highest F value i.e.0.86 and while in narrow EW rows had the poorest value (0.77). There was low RUE in early growth stages because more solar energy was used up being incident on the soil surface rather than on the plants due to inadequate development of plant canopy. The RUE showed maximum value at booting stage. There was no significant difference in the RUE among the treatments and also among interactions. The difference in the RUE was found negligible. Slightly high RUE was found in the widely spaced EW rows during in second sowing (i.e.2.07 g MJm-2) as compared to the general mean (i.e.2.01 g MJm-2). The lowest RUE was observed in wider NW rows (i.e. 1.96 g MJm-2 and 1.97 g MJm-2 for respective sowing times). There was no statistically significant difference among HI values corresponding to different treatments revealed that there was no difference in fraction of radiant energy used for grain biomass. High averaged LAI was recorded in narrow NS rows during both sowing dates (3.26 and 3.7, in respective sowing dates). Wide NS rows (2.67 and 3.38, in respective sowing dates) succeeded this treatment. The EW rows produced lower LAI. The NS rows (narrow and wide) did not show much fluctuation in the values of k (extinction coefficient), while EW rows (narrow and wide) showed comparatively more fluctuations, indicating the changes in canopy structure. The average value of leaf orientation over the entire study indicated that leaves usually preferred N (16.6 %), S (16.1%) and W (13.2%) direction. General results showed the leaves were randomly oriented with different times. The seasonal average of direct beam interception fraction (I/I0) indicated that the in general, highest direct beam interception occurred on the first leaf and lowest on the second leaf while third leaf had intermediate direct beam interception. Maximum average interception fraction was 0.63 over the third leaf and minimum (0.22) over second leaf of the wider NS rows during second sowing. While, in case of the narrow NS rows of the first sowing, second leaf had high interception with 0.61 fraction, first leaf had value 0.24 and third leaf had fraction 0.41. Except these two. values for NS oriented treatments the leaves of the other treatments showed intermediate direct beam interception fraction ranging from 0.31 to 0.51 over the entire season. Soil surface temperature was observed to be slightly high at morning hours (1000 h) in the wider EW rows during both the sowings. Those for narrow EW rows followed these values. During noon time (1300 h), wide NS rows had higher soil surface temperature than respectively that for other treatments. In afternoon, the soil surface temperature did not show much difference among treatments. The difference in the temperature was considered as the function of the radiation penetration in the rows. Wide NS rows had higher evapotranspiration, in general after early growth period. Other treatments showed no distinct pattern in this respect. The moisture loss pattern had almost parallel trends for narrow and wide rows in particular orientation. This indicated that there was influence of spacing on evapotranspiration. The results revealed that NS rows and wider spacing had high radiation penetration.
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AGRICULTURAL METEOROLOGY, AGRICULTURE, A STUDY