Yield response of wheat to sorghum extract and herbicide (affinity) application at different growth

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Introduction
In Pakistan, weeds create huge problems during production of crops because weed control is not given proper preference due to the financial status of our farmers and the absence of education.Non progressive farmers have not enough money to meet the asking price of weed management requirements carry out for the production of crops.Thus this is due to weeds that growing among crop plants and adversely affect yield and quality of the harvest and maximize production costs, with low income returns.Among weeds some of them cause serious problems to crop plants and compete for various resources for example nutrients, moisture, sunlight and space [1].Apart from competition, many other factors like lodging and harvesting problems are created by weeds.In Pakistan, weeds are accountable for 30 percent grain yield losses in wheat which amounts to Rs. 1150 million annually [2].Weed decline yield and quality of crop plants and leads to higher cost in food production [3].Therefore, weed control is one of the most important aspects of crop production in agricultural systems.For better yield weed management is very crucial factor.The type of weed control which is traditional have some flaws which include time consumption, intense labor and dependency on weather.Unnecessary use of herbicide is expensive and causes environmental problems [4] and it has also adverse effects on the nutritive value of several crops [5].Besides this, research has proved herbicides resistant weeds [6] in areas to the unnecessary and too much usage of herbicides.Allelopathy is an inexpensive, natural, environment friendly and an organic attitude to regulate weed density and proliferate crop yields as it conserve the ecosystem [7] concluded that sorghum plant is extremely allelopathic and sorghum remains could be significantly used to accomplish several vital weeds in irrigated wheat crop with no effect on the main crop in semi-arid conditions.Mature sorghum plants possess nine water soluble chemicals which are phytotoxic to certain weeds such as Phalaris minor Retz.Chenopodium album L., Rumex dentatus L., and Convolvulus arvensis L. [8, 9] used water extracts of ripened sorghum plants and described that water extract spray minimized biomass of weed from 35 to 40% and proliferated yield of wheat from 10 to 20%.Researchers have also reported that the allelochemicals production in plants is affected by numerous factors related to environment and increased amount of allelochemicals have been reported in plants developed under mineral stress and drought [10,11].Allelo-chemicals, which have the ability to exterminate some species of plants, are considered highly as these substances have the potential of working as naturally selective herbicide [12].Cultivars which are highly suppressed by weeds need allelopathic crops for their substantial development [6].Sunflowers have allelopathic properties which are published many times and this crop is famous for their herbicidal effect on numerous crops and weeds.Different sunflowers cultivars were selected by [13].andextracted 125 different allelopathic compounds which were phytotoxic for various plants.[14,15]also reported that seed germination of white mustard (Sinapis alba L.) was fully inhibited by the extracts of sunflower, while it had no effect on the viability of seeds [15].

Materials and methods
Effect of sorghum extract concentration in combination with herbicide application times on weed density and yield of wheat was evaluated at Agronomy Research Farm, The University of Agriculture Peshawar, Pakistan during 2015-16.The experiment was laid out in a randomized complete block design (RCBD) having three replications.A plot size of 3 m x 1.8 m (L x W) was used.Each plot consists of six rows having 30 cm row to row distance.Wheat variety (Atta Habib 2010) at the seed rate of 120 Kg ha -1 was sown on 21 November 2015 with the help of seed drill, and harvested on 12 May 2016 by hand sickle.Nitrogen and phosphorous fertilizers were applied at the rate of 120-90 kg ha -1 respectively, and source of N and P fertilizer were applied in the form of urea (46% N) and diammonium phosphate (46% P2O5 and 18% N).All phosphorous fertilizer and half of nitrogen were applied at the time of sowing; remaining nitrogen was applied at first irrigation.Irrigation was applied whenever required.Three factors and their levels were studied in the experiment which included: For the determination of grains spike -1 ten spikes were chosen in each plot and grains were calculated.After this process, the final data was recorded on average basis.Thousand grain weight data was recorded by taking sample of thousand grains from threshed grain of each plot and then weighed with a digital balance to calculate weight of thousand grains.Harvest index was calculated for each plot dividing grain yield on biological yield and then multiplied with .100 to get harvest index in percentage.

Statistical Analysis
All the data recorded were evaluated statistically through analysis of variance methods suitable for RCBD (randomized complete block design).Means were compared by using LSD test at 0.05 (level) of probability whenever the F-values were found significant [17].

Spikes m -2
Data concerning spike m -2 was significantly influenced by sorghum concentration (SC), affinity ratio (AR), application time (AT), R x T, C x R,controlvs rest, hand weeding vs herbicide, while herbicide sole, C x T, C x R x T, interaction were found nonsignificant (Table 1).Spike m -2 increased with decreased in sorghum concentration and maximum spike m -2 was obtained from 1:5 sorghum concentration while less spike m -2 were obtained from higher sorghum concentration 1:3.Lower dose of herbicide affinity (670g) produced less spike m -2 .Higher affinity ratios (1317g) resulted in maximum spike m -2 which was statistically at par with affinity ratio (988g).Mean values of the application time showed that sorghum herbage applied at tillering stage produced maximum spike m -2 which was statistically similar to sorghum herbage applied at emergence, while lower number of spike m -2 were observed when the treatments applied at 50 % at E + 50% at T. The greater number of spike m -2 with hand weeded, sorghum concentration and application time could be the reason of higher phytotoxic influence of herbicide on weed, on contrast, the less no. of spike meter -1 in control plot could be the reason of higher density of weed that increase the weed struggle with wheat crop for requirements such as water, nutrients, air etc.Similar results have also been reported by [18,19].They reported substantial rise in spike m -2 along with the application of herbicide.These findings are in similarity with [20] where he found substantial rise in no of spikes by the application of allelopathic extracts of many plants.

Grains spike -1
Spikes latent is detrimental if considered in number of grain spike -1 and is a significant component of yield.The statistical data confirmed that grain spike -1 was significantly influenced by sorghum concentration (SC), affinity ratio (AR), application timing (AT), control vs rest, hand weeding vs herbicide, herbicide sole vs ratio, herbicide sole and C x R, while R x T, C x T, C x R x T interaction were found non-significant (Table 2).Minimum grain spike -1 was obtained from sorghum concentration 1:3.Maximum grain spike - 1 were recorded from 1:5 which was statistically at par with sorghum concentration 1:4.Less grain spike -1 were recorded from affinity applied at (988g), while higher affinity ratio (1317 g) resulted in more grain spike -1 .Sorghum herbage applied at tillering stage produced higher grain spike -1 and it was at level mathematically with that of sorghum herbage used during emerging time while the lowest grain spike -1 were obtained from sorghum herbage used 50% during emergence + 50% during tillering stage.Maximum grain spike -1 was obtained from hand weeded plots as compare to control and the rest of treated plot.Similarly sorghum concentration, herbicide and application time gave more grain spike -1 over control plots.The reason of increased number of grain spike -1 is attributed to the effective weed control in those treatments and the wheat crop efficiently utilized all the available resources.These results are in line with [18, 21, 22] who reported that herbicide application significantly increased the grain spike -1 .In control plots, the decrease in grain spike -1 might be of the rationale that competition between weeds and wheat crop was there for growth requirements.Similar results have been shown by [20,23] where they found effectively higher grains per spike with control plots and water extracts.

Thousand grain weight (g)
Thousand grains weight was significantly affected by sorghum concentration, affinity ratios, control vs. rest, hand weeding vs. herbicide, herbicide sole vs. ratio, C x R ,R x T whereas, application timing, herbicide sole, C x T, C x R x T interaction were found non-significant (Table 3).Less thousand grain weight were recorded in higher sorghum concentration 1:3 which was statistically similar with sorghum concentration 1:4.Thousand grains weight increased with decreasing sorghum concentration 1:5.Higher affinity ratios (1317 g) resulted in higher thousand grains weight which was statistically at par with affinity ratio (988 g).Lower affinity dose (670 g) resulted in lower thousand grain weight.Maximum thousand grains weight were recorded in hand weeded plots in comparison to control.Mean values for application time revealed that treatments applied at tillering time gave maximum thousand grain weight.Highest grain weight might be due to successful weed control in treated plots.It could be due to the action of various types of allelochemicals present in allelopathic plants that were used in the form of water extracts.Extracts of tested species might have the potential to be used for weed control [24].[25] also reported significantly positive effects of sorghum WE spray on 1000-grain weight.The increased grain weight could be attributed to the availability of resources to the wheat crop.Our results are in line with the finding of [26] who concluded that maximum 1000 grain weight was recorded in those plots which were treated with the mixture of herbicides, while minimum in weedy check plots.
[27] also reported that herbicide treated plots gave higher 1000 grain weight than the weedy check plots.

Harvest index (%)
Sorghum concentration (SC), affinity ratio (AR), application timing (AT), herbicide sole vs. ratio and R x T significantly affected to harvest index whereas, control vs. rest, hand weeding vs. herbicide, herbicide sole, C x R, C x T, C x R x T interaction were found non-significant (Table 4).Maximum harvest index were recorded from 1:5.Higher affinity ratio (1317 g) resulted in higher grain yield.Sorghum herbage applied at tillering stage or50% during emerging stage + 50% at tillering produced higher harvest index, while the lowest harvest index were obtained from sorghum herbage applied at emergence.The relationship between biological yield and economic yield is termed as Harvest index, for this reason, high harvest index with sorghum concentration, hand weeding, herbicide and application timing could be the reason that increased grain yield which then caused high harvest index in wheat crop.Similar findings have also been reported by [28,29] where they found substantial increase in Harvest index through various concentrations of water extract that contained allelochemicals.Same findings have also been published by [20] where they found that harvest index and all other parameters were enhanced by herbicide application.

Conclusion
It was concluded that the combination of sorghum water extract 1:5 and herbicide 1317g ha -1 (2/3) of the recommended dose of affinity applied at tillering stage significantly increased yield components and maximized net return of wheat crop.

Authors' contributions
yield (kg ha ) 100 Biological yield (kg ha )  Economic analysis were carried out by calculating marginal rate of return (MMR) as done by [16].To determine (MMR) total cost of treatment first and second, net benefits of the treatment first and second and their difference were calculated and then multiplied with 100 as in the formula given below.Similar process was repeated for all other treatments.
Conceived and designed the experiments: SK Khalil & A Tabassum, Performed the experiments: A Tabassum, Analyzed the data: A Tabassum, T Shah & M Alamzeb, Contributed reagents/ materials/ analysis tools: Z Rahman, Misbahullah, S Khan,

Table 5 .Economic analysis of sorghum extract concentrations with combination of herbicide application time Treatments Grain yield (kg ha -1 )
Grain recent market price = Rs.32kg - Straw recent market price =Rs.12kg -1 Herbicide price (Affinity)=800 per 800 g Hand weeding = 500Rs.Person -1 per day