EFFECTS OF DIFFERENT WEEDING TIME OF RYEGRASS ON GROWTH AND YIELD COMPONENTS OF WHEAT (Triticum spp.) IN JIMMA ARE, SOUTH WEST ETHIOPIA

The experiment was conducted at Jimma University College of Agricultures and Veterinary Medicine (JUCAVM) under field condition to determine the effects of different weeding time of Ryegrass on growth and yield components of Wheat (Triticum spp.) The experimental design used was randomized complete block design (RCBD) and each of the experimental treatment was replicated three times. A Wheat cultivar, Digalu was grown with Ryegrass and different weeding time of Ryegrass T1 (weeding 15-45 DAS), T2 (weeding 30-60 DAS), T3 (weeding 45-75 DAS), T4 (weed free) and T5 (no weeding) were used as a treatment. Data were recorded on Wheat Plant height, Stem thickness, Number of tillers; Spike length and Spike number. The result revealed that various weeding time of Ryegrass statistically (p≤0.05) affected Plant height, Stem thickness, Number of tillers; Spike length and Spike number. The maximum values of all the parameters were recorded in the (15-45 DAS) except for Plant height and Stem thickness. Whereas, the minimum values of these parameters were recorded from (45-75 DAS) except for Plant height. It is advisable for growers to remove the Ryegrass before the critical weed-crop competition period which is most probably (15-45 DAS) to keep the crop weed free at this period.


INTRODUCTION
Wheat (Triticum spp.) is a cereal grain, originally from the Levant region of the Near East but now cultivated worldwide (Peter, 2009) [12] . In 2013, world production of Wheat was 713 million tons, making it the third most-produced cereal after maize (1,016 million tons) and rice (745 Http://www.granthaalayah.com ©International Journal of Research -GRANTHAALAYAH [111][112][113][114][115][116][117] million tons) (FAO Stat, 2015) [4] .Average yield of wheat in Ethiopia(1.3 t/ha) Hailu (2003), [7] is very low compared to New Zealand, Netherlands, Ecuador and France (8.9, 8.6, 8.0 and 7.6 t/ha) (FAO, 2013) [5] .Ethiopia is the second largest wheat producer in sub-Saharan Africa, after South Africa. Although most of the wheat grown in Ethiopia is bread Wheat, there is some durum wheat which is often grown mixed with bread Wheat. Wheat is among the most important crops in Ethiopia, ranking fourth in total cereals production next to Maize, Sorghum and Teff (CSA, 2009) [2] .
Studies indicated that crop losses due to Weed competition throughout the world as a whole, are greater than those resulting from combined effect of Insect pests and diseases (Gella et al., 2013) [6] .There are innumerable reports on negative effects of Weeds on crop plants (Javaid et al., 2007) [8] thus cause huge yield losses (Rathore et al., 2014) [13] . Unchecked weed growth reduces crop yield up to 57% (Singh et al.,1997) [16] .Weed infestation may reduce yield by 45.5 to 63.9% (Reddy and Reddi, 2002) [14] , in Wheat while reduced up to 92% by competition from Ryegrass (Dickson et al., 2011) [3] .
Rye grass can germinate, emerge, and establish over a range of environment. As it is in the same family with Wheat, Barley and Oat, it is known to affect the growth of Wheat, Barley, Oat and other crops by competing for each requirements of Wheat. In Wheat, yield reductions depend on the relative densities of the Weed and crop, relative times of emergence, staying with crops, weeding and resources available to each species. Ryegrass affects Wheat tillers and spikes to decrease in number, stem thickness decrease or become thin and spikes size become small but plant height increase as they compete for light conditions (Bond et al, 2014; Nandula et al, 2009) [1] [10] Weeds are one of the major constraints of Wheat production and Weed control is the key Factor in increasing yield (Lopez-Granados, 2011; Shehzad et al., 2012) [9] [15] .Weed control has been observed as one of the most important practice in crop production because good Weed control will ensure maximum yield and high quality of farm produce (Njoroge, 1999) [11] .
According to Hailu (2003) [7] , despite the importance of Wheat in Ethiopia, the mean national yield (1.3 t/ha) is 24% below the mean yield of Africa and 48% the global due to Weed infestation. Therefore, the objective of this study was to investigate effects of different weeding time of Ryegrass on growth and yield components of Wheat (Triticum spp.) under field condition. estimated to be 1500mm. The soil type of this area is characteristically reddish brown clay soil with P H of 5.06-6.00.

Materials used:
Ryegrass seed, clean Wheat seed (Digalu cultivar), digging material, shovel, meter and rope were used.

Treatments and experimental design:
The experiment was carried out on 33.6m 2 consisted of 5 treatments: T 1 (weeding 15-45 DAS), T 2 (weeding 30-60 DAS), T 3 (weeding 45-75 DAS), T 4 (weed free) and T 5 (no weeding). The experiments were laid out as completely randomized block design (CRBD) replicated three times. Thus, there were 5 x 3 treatments, which were replicated three times, resulting in 15 experimental units. Each treatment was conducted on 1.05 m by 1 m plot size and replicated three times with 70 seeds of Ryegrass and Wheat per plot except T 4 (weed free) sown only Wheat seed. The spaces between plots and blocks used were 0.6m and 0.7m respectively.

PROCEDURES FOR SITE PREPARATION
1) The land was ploughed three times with oxen 2) 33.66 m 2 of land was measured with meter which was 7.65 m by 4.4 m and checked by Pythagoras theorem 3) The field was divided in to three blocks and each block was divided in to five plots of 1.05 m by 1 m size and the plots were watered properly. 4) Finally 70 seeds of wheat (Digalu cultivar) were sown in row with spacing of 0.15 m and 0.10 m between rows and plants respectively and 70 seeds of ryegrass were sown in row by drilling. All treatments except the control group (weed free) were managed by weeding once a week to keep weed free for 30 days after starting weeding but all of them were watered, applied Urea and kept from other weeds in the same way.

DATA COLLECTION AND ANALYSIS
Data was collected from five central rows of each plot using the following parameters: Plant height (cm), Stem thickness (cm), Number of tillers, Spike length (cm) and Spike number every week fifteen days after planting. Data of each parameter from each plot and replication was collected and analyzed by analysis of their variance (using ANOVA). The data was analyzed by SAS computer software.

RESULTS AND DISCUSSIONS:
Data was collected from five central rows of each plot. Five plants were selected and collected randomly from each plot. The following parameters were taken during data collection:

PLANT HEIGHT
Analysis of variance result showed that there were significant (p≤ 0.05) differences on Plant height and Spike number due to effect of Ryegrass weed (Table 1). Ryegrass weed has effect on Wheat plant height. As both of them compete for light so as to not to be shaded each other, the plant increases in height than that of weed free or usual plant height. This effect varies with the weed-crop competition period and time of weeding i.e. plant height increases during critical weed-crop competition period than the time after and before this period. This research result showed that there was significant difference in Plant height. This difference occurred between T 4 (weed free) with an average height of (60.09cm) and the rest treatments were showed no significant difference between treatment T 1 , T 2 , T 3 and T 5 with an average height of (66.5 cm, 65.9 cm, 67.5 cm and 67.7 cm) respectively (table 2 below) as there was more or less crop-weed competition until the weed had been removed in treatment T 1 , T 2 and T 3 and stay weedy in treatment T 5 .

NUMBER OF TILLERS
Very highly significant (p<. 0001) differences were observed at Number of tillers, Spike number and Stem thickness due to effect of Ryegrass weed (

SPIKE LENGTH
Ryegrass affects the spike length or size of the Wheat as it competes with Wheat for nutrients and other requirements to develop good spike height or size. The effect can be minimized by removing or weeding the Ryegrass before the critical weed-crop competition period. This research result revealed significant difference in spike length. There was significant difference between T 1 and T 3 with (9.7333 cm) and (7.6733 cm) average spike length respectively and between T 2 and T 5 with an average spike length of (8.9567 cm) and (6.9933 cm) respectively. But no significant difference was recorded between T 1 , T 2 and T 4 which showed spike length of (9.7333 cm, 8.9567 cm and9.7933 cm) respectively. And also no significant difference was observed between T 2 and T 3 with an average spike length of (8.9567 cm) and (7.6733 cm) respectively and between T 3 and T 5 with an average spike length of (7.6733 cm) and (6.9933 cm) respectively (table 2).

SPIKE NUMBER
Wheat crop which is infested by Ryegrass weed results in spike number reduction because the number of tillers becomes decreased and some of the tillers may not reach at spike bearing or heading stage due to the Ryegrass competition effect. This effect of Ryegrass on Wheat spike number varies with the growth stage of both plants i.e. early weed-crop competition followed by weeding before tillering has minimum effect whereas the effect becomes high if the wheat crop stays weedy during tiller formation and critical weed-crop competition period. This research result showed high significant difference of weeding time of Ryegrass on Wheat crop spike number. There was significant difference between T 1 , T 2 and T 3 with an average spike number of (12.3333, 7.3 and 4.59) respectively and between T 2 and T 5 with an average spike number of (7.3) and (3.8) respectively. However, no significant difference was observed between T 1 and T 4 with an average spike number of (12.3333) and (12.4333) per plant respectively and between T 3 and T 5 with an average spike number of (4.59 and 3.8) per plant respectively (table 2).

STEM THICKNESS
Ryegrass has negative impact on Wheat stem thickness as it competes with Wheat crop for common resources such as nutrients, moisture, minerals and sunlight. The stem of the Wheat infested by Ryegrass becomes thinner than that of the Wheat which is weed free and early weed infested followed by removing the Ryegrass before critical weed-crop competition period. The research conducted showed high significant difference of Ryegrass weeding time on Wheat stem thickness (table 2 below).There was significant difference between each treatment which means that the Ryegrass affected the Wheat stem thickness staring from early growth up to the beginning of maturity with less to high severity. T 1 (15-45 DAS) which resulted with an average stem thickness of (1.83333 cm) which was good thickness relative to T 4 weed free with an average stem thickness of (1.97333 cm). However, the least stem thickness was recorded from T 3 (45-75 DAS) with an average stem thickness of (1.48667) as compared to T 1 and T 4

CONCLUSION
Generally, being able to determine the growth stage of Wheat and Ryegrass at which they compete more, less or no competition is a crucial requirement to manage and accomplish different cultural practices properly and at correct time during the growing season. Fertilizers, pesticides and other chemicals should or should not be applied at certain points during the plant growth. By understanding what stage the plant is in, can be determined the correct cultural practices. Depending on this research result, the approximate correct time of Rye weeding or removing from the Wheat crop in the field should be at the early growth stage before tiller formation stop and reach at critical weed-crop competition period which is 15 -45 Days After Sowing.

ACKNOWLEDGEMENTS
The Authors would like to thank Jimma University College of Agricultures and Veterinary Medicine (JUCAVM) for funding the research expenses and providing all the necessary facilities to carry out the research.