Influence of different weed management practices on yield and nutrient dynamics in groundnut

Introduction

Groundnut is also know as king of oilseeds, which contains both oil and protien about 45 to 53% and 26% respectively. Weeds compete with crop plants for nutrients, moisture, space and light and reduce not only the crop yields but also quality of produce. So, timely weed management is needed for getting higher yield. In groundnut, initial 30 days are crucial because its intial slow growth of with less number of branches, allows severe infestation of weeds which reduces the yield to an extent of 33% (DWR, 2015) [1] . However, weed management by hand weeding has become unfeasible due to a lack of labour and increasing wages. Herbicides are the best alternative for weed control in such conditions. So present study was conducted to know the extent of nutrient loss by the crop and weed under different management practices.

Materials and Methods

A field experiment was conducted during Rabi 2020-21 in sandy loam textured soil college farm of Agricultural College, Bapatla, Andhra Pradesh. The soil was low in organic carbon (0.25%), available nitrogen (188 kg ha -1 ), available potassium (211.5 kg ha -1 ), and available phosphorus (21.7 kg ha -1 ). Healthy and sound groundnut kernel of "DHARANI" was sown on 15 October, 2020 at spacing of 22.5 x 10 cm by using seed rate of 150 kg/ha. The crop was harvested on 30th January 2021. Nine weed management practices consisted of preemergence (PE) application of Weedy check, Hand weeding at 20DAS and 40DAS, Alachlor @ 1.5 kg a.i ha -1 as PE fb hand weeding at 30 DAS, Imazethapyr @ 50 g a.i ha -1 as PoE, Quizalofop ethyl @ 50 g a.i ha -1 as PoE, Alachlor@ 1.5 kg a.i ha -1 as PE fb hand weeding at 30DAS, Propaquizafop @ 50g + imazethapyr @ 75 ga.i ha -1 as PoE at 20 DAS, Acifluorfen @ 160g + clodinafop propargyl @ 80 g a.i ha -1 as PoE at 20DAS, Fomesafen @ 110g + fluazifop-p-butyl @ 110 g a.i ha -1 as PoE at 20 DAS (Table 01). The experiment was laid out in randomized block design with three replications. Pre-and post-emergence herbicides were applied at one and 20 DAS by using battery operated knapsack sprayer fitted with flat-fan nozzle with spray fluid of 500 L/ha. The crop was supplied with recommended fertilizer dose of fertilizers with 30 kg N, 40 kg P 2 O 5 and 50 kg K 2 O per ha through urea, single super phosphate and murate of potash, respectively to all the plots as basal, Top dressing of 10 kg of N was applied in form of urea at 25 DAS. The unweeded check plots were allowed to remain infested with weeds till harvesting of the crop. The data was recorded as per standard procedures and analyzed using ANOVA and the significance was tested by Fisher's least significance difference (p=0.05), Gomez and Gomez (1984) [3] . The nutrient content in soil were analyzed as suggested by Subbiah and Asija (1956) [8] for N, Olsen's method for P and neutral normal ammonium acetate method for K (Jackson 1973) [4] .

Results and Discussion

The predominant weed species observed in the experimental field were Cynodon dactylon, Digitaria sanguinalis and Panicum repens, sedge Cyperus rotundus and broad-leaved weeds like Trichodesma indica, Cleome viscosa, Indigiofera hirsuta and Phyllanthus niruri. All the weed management practices significantly influenced the weed growth, and nutrient uptake. The lowest weed density and weed dry weight of weeds were recorded with two hand weedings at 20 and 40 DAS and alachlor @ 1.5 kg a.i. ha -1 as PE fb hand weeding at 30 DAS. Both the weed management practices were performed better throughout the crop growth period and significantly superior in reducing density and dry weight of all the category weeds and comparable with fomesafen @ 110 g + fluazifop-p-butyl @ 110 g a.i ha -1 at 20 DAS. The data revealed that, higher N, P and K uptake was recorded with the treatment where hand weeding at 20 and 40 DAS followed by alachlor @ 1.5 kg a.i ha -1 as PE fb hand weeding at 30 DAS and propaquizafop @ 50 g + imazethapyr @ 75 g a.i ha -1 as PoE at 20 DAS, this was due to treatments involving inter cultivation (hand weeding) practice and post-emergence herbicides in combination showed higher dry matter production resulting higher nutrient uptake by the crop. This might be due to less weed competition in these plots throughout the crop growth period. These results were in accordance with the findings of Divyamani et al. (2018) [2] and Naveen et al. (2019) [5] . Whereas the lowest nutrient removal by weeds is with fomesafen @ 110 g + fluazifop-butyl @ 110 g a.i. ha -1 as PoE at 20 DAS and Propaquizafop @ 50g + imazethapyr @ 75 ga.i ha -1 as PoE at 20 DAS, among the post emergence herbicides studied. Nutrient removal by weeds is in the reverse order as that of nutrient uptake by crop. There is a positive correlation between nutrient uptake by crops and yield. Similarly, there is a negative correlation between nutrient removal by weeds and yield. Hencethe podl yield will be higher whenever the nutrient uptake by crop is higher and nutrient removal by weeds is lower. Weeds deplete the soil nutrients rapidly than the crop, hence, the soil with higher population of weeds will have lower soil fertility levels when compared to an exhaustive crop. Poor soil nutrient status was recorded with unweeded control due to high weed density and dry weight. Srinivasarao et al. (2011) [7] and Naveen et al. (2019) [5] .

Conclusion

According to the results of the study, Hand weeding at 20 and 40 DAS was found to be superior over other treatments. Among the post emergence herbicides studied, higher N, P and K uptake was recorded with the fomesafen @ 110 g + fluazifop-butyl @ 110 g a.i. ha -1 as PoE at 20 DAS but the yield was reduced due to its phytotoxic effect. Application of propaquizafop @ 50 g + imazethapyr @ 75 g a.i ha -1 as PoE at 20 DAS yielded equivalent pod yield to hand weeding at 20 and 40 DAS among the post-emergence herbicides. As chemical weed control alone doesn't contribute to long term sustainability, the herbicide compatibility in integrated weed management should be tested in further studies.

References

1. Directorate of Weed Research (DWR), Indian Council of Agricultural Research (ICAR). Jabalpur, Madhya Pradesh; 2015. Available from: www.dwr.org.in
2. Divyamani B, Reddi RY, Subramanyam D. Yield and nutrient uptake in rabi groundnut as influenced by different weed management practices. J Pharmacogn Phytochem. 2018;7(5):3166-3168.
3. Naveen B, Subramanyam D, Nagavani AV, Umamahesh V. Weed management in groundnut with new herbicide molecules. Indian J Weed Sci. 2019;51(3):306-307.
4. Srinivasarao S, Madhavi M, Reddy RC. Integrated approaches for weed control in rabi groundnut. J Res ANGRAU. 2011;39(1&2):60-63.
5. Subbiah BV, Asija GL. A rapid procedure for determination of available nitrogen in soil. Curr Sci. 1956;25:259-260.