Non-herbicidal Weed and Organic Nutrient Management in Maize under Rainfed Maize-Sesamum Cropping Sequence

Maize is the third most important food grain followed by rice and wheat in India. Maize is used for human consumption both with and without industrial processing, as animal feeds and bio-chemical industries. Maize is called as the queen of cereals due to its high yielding ability. Maize is mostly cultivated during rainy season in our country and weeds are a major problem during this period of time because of amble availability of growth factors during this season. Several research workers had observed that if weed competition in maize was left unchecked it would result in serious yield loss ^1,2,3. Weed management strategies are focused on reducing the deleterious competition of weeds growing with crop plants for growth factors⁴. It is a well documented fact that due to rise in environment pollution, various human health related issues have arisen which have led the human race to advocate for reduction in the pollution for a greener earth. Agriculture too has a share in the contribution towards environment pollution through the indiscriminate use of synthetic agro-chemicals. Researchers are constantly working on bringing out techniques that would curtail the agriculture dependence on synthetic agro-chemicals while not compromising with the issue of feeding the ever growing population on earth. Manual weeding followed by earthing up⁵, hoeing twice⁶ and live mulching combined with hand weeding⁷ were documented to be effective in suppressing the weeds in maize. In India, maize-wheat or maize-rapeseed rotations are prevalent. Maize is usually mono cropped or in cultivated in rotation with greengram or blackgram in Assam⁸. The farming in the North eastern region is organic by default as the application of fertilizers and pesticides are limited compared to the other regions of the country. Maize organically cultivated may be followed by sesamum crop, an important oilseed crop of India which have a low nutrient requirement⁹. Researcher^10,11 have noticed residual effect of compost application in different cropping sequence. Researches on non-herbicidal weed and organic nutrient management in maize-sesamum cropping sequence in Assam are lacking. Considering all the points discussed above, the present experiment was done.

Materials and Methods

Site Location

During the year 2012-2013 and 2013-2014, the field experiment was done at the Instructional-Cum-Research (ICR) farm, Assam Agricultural University, Jorhat.

Treatments, layout and initial soil chemical status of the experimental field

The experiment was conducted in split plot design. The main factor was fertility management (F₀ – control, F₁ – 2.5 t/ha enriched compost and F₂ – 5.0 t/ha enriched compost) and the sub factor was weed management (W₀-no weeding, W₁– hand hoeing and earthing up 20 and 50 days after sowing,W₂–in situ cowpea mulching upto 50 days after sowing and W₃– in situ blackgram mulching upto 50 days after sowing). The treatments were incorporated in maize and its effects were carried over to the succeeding crop sesamum. The enriched compost was procured from the department of soil science, Assam Agricultural University, Jorhat. Enrichment was done by addition of rock phosphate. The research plot soil was sandy loam in texture with acidic in reaction (pH 5.33). The soil organic C value was 0.51%, available N was 318.93 kg/ha, available P₂O₅ was 32.95 kg/ha and available K₂O was 167.54 kg/ha^9,12.

Crop Varieties Used

Varieties used in the experiment were as follows, maize variety-Dekalb 900 m Gold, sesamum-Koliabor Til, cowpea-UPC-212, blackgram-T9^9,12.

Weed Analysis

The weeds present within a quadrate (50 cm x 50 cm) placed randomly at four locations in each individual plot were removed at 60 days after sowing (DAS) and during harvest of maize and sesamum. The weeds were cleaned and oven-dried at 60±5°C to constant dry weight, finely grounded with a grinding machine and chemically analysed for NPK content. The methods of chemical analysis followed were-

1. Nitrogen-Micro Kjeldahl method¹³
2. Phosphorus-Vanadomolybdate yellow colour (colorimetric) method¹³
3. Potassium-Flame photometer method¹³

For the total NPK uptake by weeds, it was calculated using the following formula:

Nutrient uptake = [Nutrient content/100] × Biomass (kg/ha)

Growth Analysis

In case of maize, length of the fully opened leaf lamina was measured from the base to the tip. Leaf breadth was taken at the widest point of the leaf lamina. The product of the leaf length and breadth were multiplied by the factor 0.75¹⁴ and the sum of all the leaves were expressed as leaf area in cm²/plant. Finally the average was calculated to get the data of each plot. This observation was recorded at 30, 60 and 90 DAS. Leaf area index (LAI) for maize and sesamum were calculated by dividing the leaf area/plant by the land area occupied by single plant. In sesamum, length of the leaf lamina was measured from the base to the tip. Leaf breadth was taken at the widest point of the leaf lamina. The product of the leaf length and breadth was multiplied by the factor 0.709¹⁵ and the sum of all the leaves was expressed as leaf area in cm²/plant. Finally the averages were calculated out. This observation was recorded at 30, 60 and 90 DAS. Days to 50% tasseling was recorded on the day when 50 % maize plants had attained tasseling stage. This data was recorded for individual plot. Days to 50% flowering was recorded on the day when 50% sesamum plants had attained flowering stage. This data was recorded for individual plot.

Yield Analysis

At physiological maturity, maize cobs from each net plot were harvested. Cobs were separated, air dried, shelled, cleaned and weighed. Grain yield per ha was worked out and expressed in kg/ha. In sesamum, during harvest, net plot was harvested separately and bundled. Bundles were dried in sunshine. Later seeds were separated from the bundles separately for each individual plot manually by tapping with a stick. The produce was dried, winnowed, cleaned and weight of seeds obtained from each net plot was recorded expressed in kg/ha.

Benefit

Cost Ratio Analysis

This was calculated by dividing the net retun by total cost of cultivation.

Statistical Analysis

All the data pertaining to the present investigation was analysed following the procedure of analysis of variance¹⁶. Significance or non-significane of variance was determined by calculating respective ‘F’ values. Whenever the variance ratio (P) was found significant, critical difference (CD) was worked out at 5% probability level.

Results and Discussion

Content (%) and uptake (kg/ha) of NPK by weeds in maize at 60 days and at harvest         

Fertility Management

The data given in Table 1 and Table 2 revealed no significant effect of fertility management by organic nutrition in maize on content (%) and uptake (kg/ha) of NPK of weeds in maize at 60 days and harvest.

Weed Management

Non-herbicidal weed management in maize resulted in significant effect (Table 1 and Table 2). It was noted that at 60 DAS, W₁ resulted in the least nutrient content of N (1.50%, 1.47% during 2013 and 2014, respectively), P (0.232%, 0.227% during 2013 and 2014, respectively) and K (1.15%, 1.12% during 2013 and 2014, respectively). At harvest of maize, W₂ resulted in the least content of N (1.24%, 1.21% at harvest during 2013 and 2014, respectively), P (0.230%, 0.224% at harvest during 2013 and 2014, respectively) and K (1.03%, 1.24% K at harvest during 2013 and 2014, respectively). In terms of uptake, during 60 DAS and harvest, W­₁ resulted in the least uptake of N (0.49 kg/ha and 0.47 kg/ha at 60 days, 7.14 kg/ha and 6.89 kg/ha at harvest during 2013 and 2014, respectively), P (0.08 kg/ha and 0.07 kg/ha at 60 days, 1.18 kg/ha and 1.11 kg/ha at harvest during 2013 and 2014, respectively) and K (0.38 kg/ha, 0.36 kg/ha at 60 days, 6.16 kg/ha and 7.14 kg/ha at harvest during 2013 and 2014, respectively). Highest content (%) and uptake (kg/ha) at 60 days and at harvest by weeds in maize was recorded in case of W₀ during 2013 and 2014.

Table 1: Effect of Weed Management and Fertility Management on NPK Content (%) and Uptake (Kg/Ha) Of Weeds in Maize at 60 DAS

NS Not significant; DAS Days after sowing

Table 2: Effect of Weed Management and Fertility Management on NPK Content (%) and Uptake (Kg/Ha) of Weeds in Maize at Harvest

NS Not significant; DAS Days after sowing

Interaction

No significant interaction effect between fertility management by organic nutrition and non-herbicidal weed management in maize on NPK content (%) and uptake (kg/ha) of weeds in maize at 60 DAS and harvest.

No significant effect due to fertility management on weeds was found in the present experiment. Organic manures had no significant effect on dicot weeds while significant effect was observed only on monocot weeds in fennel¹⁷. A study of the results on NPK content (%) of weeds revealed that the trend at harvest of maize were totally different as compared to that made at 60 DAS. Significantly more NPK content (%) of weeds at harvest of maize in case of W₁ compared to other treatments. The soil disturbances at 50 DAS due to W₁ might have encouraged emergence of new weeds later on and their density being less at harvest of maize resulted in more NPK content of weeds. However, it was not detrimental to maize as the critical period of crop-weed competition was over after 50 DAS. Significantly the lowest NPK content of weeds in case of W₂ was due to smothering of weeds. The findings regarding NPK uptake (kg/ha) of weeds at harvest in maize as described above reflected the similar trend as observed at 60 days. Though low NPK content of weeds was observed in W₂ it could not reduce the weeds NPK uptake. It was due to the fact that this treatment was unable to substantially decrease the weeds density and dry weight. As the density and dry weight of weeds were significantly lesser due to W₁, uptake of NPK in weeds was found to be significantly lesser too as compared to other treatments. No weeding resulted in the maximum uptake of NP nutrients by weeds in maize as compared to two hand weeding¹⁸.

Content (%) and uptake (kg/ha) of NPK by weeds in sesamum at 60 days and harvest

Fertility, weed management and their interaction in maize could not significantly influence the NPK content (%) and uptake (kg/ha) of weeds in sesamum at 60 days and at harvest (Table 3 and Table 4). As in the preceding crop maize fertility management with enriched compost application did not have significant effect on weeds, therefore similar effect in respect of weeds during the sesamum crop was quite obvious. No residual effect of herbicides as well as hand weeding twice applied in rice on succeeding blackgram was observed¹⁹.

Table 3: NPK Content (%) and Uptake (Kg) of Weeds in Sesamum at 60 DAS as Affected by Weed Management and Fertility Management

NS Not significant; DAS Days after sowing

Table 4: NPK Content (%) and Uptake (Kg) of Weeds in Sesamum at Harvest as Affected by Weed Management and Fertility Management

NS Not significant; DAS Days after sowing

LAI, days to 50% tasseling and yield of maizeFertility management

The LAI, days to 50% tasseling and yield of maize were found to be significantly affected due to fertility management by organic nutrition (Table 5). Best LAI (0.43 and 0.40 at 30 DAS, 2.30 and 2.24 at 60 DAS and 2.14, 1.98 at 90 DAS during 2013 and 2014, respectively) and maize grain yield¹² (2322.33 kg/ha and 2178.29 kg/ha during 2013 and 2014, respectively) were as a result of F₂ application. Application of F₁ was the second best in this regard. In case of days to 50% tasseling, F­₂ (58.17 and 58.83 DAS) and F₁ (58.17 and 59.08 DAS) were statistically at par and resulted in the least number of days for the maize plants to attain 50% tasseling as compared with F₀.

Table 5: Effect of Weed Management and Fertility Management on Growth, Yield of Maize and Sesamum Click here to View Table

** Significant; NS Not significant

F- Fertility management, W- Weed management F₀ – Control, F₁ – 2.5 t/ha Enriched Compost, F₂ – 5.0 t/ha Enriched Compost; W₀ – No weeding, W₁ – Hand hoeing and earthing  up 20 and 50 DAS, W₂ – In situ cowpea mulching upto 50 DAS, W₃ – In situ blackgram mulching upto 50 DAS

Weed Management

Effect of non-herbicidal weed management was significant (Table 5). It was noticed that highest LAI (0.43 and 0.41 at 30 DAS, 2.52 and 2.46 at 60 DAS and 2.33, 2.15 at 90 DAS in 2013 and 2014, respectively) and grain yield¹² (3014.59 kg/ha and 2849.24 kg/ha for 2013 and 2014, respectively) were recorded with W₁. Days to 50% tasseling was found to be significantly decreased due to W₁ (56.44 and 57.56 DAS at 2013 and 2014, respectively).

Interaction

Interaction of the weed and nutrient management had significant effect on the LAI, days to 50% tasseling and maize grain yield (Table 6). At the same level of organic nutrition (F), W₁ outperform the other treatments and at the same or different level of non-herbicidal weed management (W), F₂ showed better result than the other treatments in respect of both LAI and days to 50% tasseling. Among the various treatment combination, application of F₂W₁ caused significantly the highest LAI (0.53, 0.51 at 30 DAS, 3.41, 3.35 at 60 DAS and 3.28, 2.85 at 90 DAS in the 2013 and 2014, respectively) than the rest of the treatments. Application of F₁W₁ was the second best treatment in this regard. The treatment combinations, F₂W₁, F₁W₁, both being statistically at par among themselves (56.33 days in 2013 and 57.33 days in 2014 for both the treatment combinations) were able to significantly decrease days to 50% tasseling in maize.

Table 6: Interaction Effects of Weed Management and Fertility Management on Growth, Yield of Maize and Sesamum Click here to view Table

F- Fertility management, W- Weed management F₀ – Control, F₁ – 2.5 t/ha Enriched Compost, F₂ – 5.0 t/ha Enriched Compost; W₀ – No weeding, W₁ – Hand hoeing and earthing  up 20 and 50 DAS, W₂ – In situ cowpea mulching upto 50 DAS, W₃ – In situ blackgram mulching upto 50 DAS

D₁ Difference of two W means at the same level of F; D₂ Difference of two F means at the same or different level of W

While considering the same level of organic nutrition (F), W₁ produced the highest grain yield. Taking into account the same or different level of non-herbicidal weed management (W), F₂ resulted in the highest maize grain yield¹². Amongst the treatment combinations, F₂W₁ was the best in terms of grain yield of maize during both the years. 

Perusal of the results on the effects of the treatments of the present experiment on revealed that LAI, days to 50 % tasseling and yield of maize were significantly improved due to application of enriched compost and non-herbicidal weed management. This was due to the fact that non-herbicidal weed management by W₁ could significantly reduce the weed infestation in maize, and therefore, the growth attributes and ultimately the yield of maize significantly improved by organic nutrition through application of enriched compost in maize. Thus, the combination of F₂W₁ was found to be significantly the best followed by F₁W₁ in respect of the growth attributing characteristic and yield. Weed management by W₁ could significantly reduce the weed infestation till the critical period of crop-weed competition in maize thereby giving the opportunity to the maize plants to tap the growth factors from their environment with less stress from the weeds compared to other treatments. The benefits of organic nutrition through enriched compost @ 2.5 t/ha and 5.0 t/ha could only be realised by the effective management of the weeds which were evident by the data obtained. Two hand weeding applied in maize resulted in better growth attributes as compared to no weeding at all⁴. The efficacy of non-herbicidal methods in managing the weeds and increasing the yield in maize was highlighted by several workers^20,21,22. Efficiency of organic nutrition in improving the growth and yield of maize was reported by various workers^23,24. In case of in situ cowpea live mulching, even though the weed NPK content and uptake were significantly reduced compared to in situ blackgram live mulching upto 50 DAS and weedy check, in situ cowpea live mulching proved to be detrimental to the maize plants because it competed with the crop for growth factors thereby negating its weed suppressing ability which was reflected in poor growth of maize plants. In situ blackgram live mulching was poor in suppressing the weeds and thus the combined effect of blackgram plants and weeds depressed the growth of the maize plant. Competition from live mulches for growth factors with the main crop thereby causing yield loss of the main crop had been reported²⁵.

LAI, days to 50% flowering and yield of sesamum

Fertility Management

The data revealed significant residual effect of fertility management by organic nutrition in maize on LAI, days to 50% flowering and yield of sesamum (Table 5). Application of F₂ resulted in significantly more LAI (0.28, 0.19 at 30 DAS; 1.60, 1.27 at 60 DAS; 0.36, 0.26 at 90 DAS during 2013 and 2014, respectively). It was found that F₂ (37.67 and 38.00 DAS during 2013 and 2014, respectively) and F₁ (38.08 and 38.50 DAS during 2013 and 2014, respectively) were at par and caused lesser days to 50% flowering than F₀. Considering the yield of sesamum¹², F₂ (589.08 kg/ha) and F₁ (556.28 kg/ha) being at par were better than F₀ in 2013 while in 2014, F₂ (402.78 kg/ha) was the best than the rest.

Weed Management

No significant residual effect due to non-herbicidal weed management in maize on LAI, days to 50% flowering and seed yield in the succeeding crop sesamum was observed (Table 5).

Interaction

Interaction between fertility management and non-herbicidal weed management in maize on LAI, days to 50% flowering and seed yield in sesamum had significant residual effect only in 2014 (Table 6). During that year, at the same level of F₀, non-herbicidal weed management treatments in maize could not significantly change the LAI in sesamum as observed at 30 and 90 DAS and similarly days to 50% flowering also, but at 60 DAS, W₁ could significantly increase the LAI in succeeding sesamum crop in comparison with the other treatments. Similar results were obtained at F₁. Now with F₂ application in maize, W₀, W₂ and W₃ could significantly increase the LAI at 30 DAS and significantly decrease the days to 50% flowering compared with W₁. At 60 DAS, W₀ and W₂ were similar but significantly better than W₁ and W₃ in respect of LAI whereas at 90 DAS, no non-herbicidal treatments proved to be significantly more effective than W₀. A perusal of the data indicated that at the same or different level of non-herbicidal weed management (W), F₁W₀, F₁W₁, F₁W₃, F₂W₀, F₂W₂ and F₂W₃ combinations were statistically similar and resulted in significantly more LAI at 30 DAS and significantly lesser days to 50% flowering in sesamum than the other combinations. On the other hand, at 60 DAS, F₂W₀ and F₂W₂, both being statistically at par, resulted in significantly more LAI whereas at 90 DAS, F₂W₀, F₂W₂ and F₂W₃ being statistically similar resulted in significantly more LAI in sesamum.

Taking into account the same level of fertility (F₀), in terms of seed yield of sesamum¹², W₁ was the best treatment. At the same level of F₁, W₁ and W₃ being at par, both recorded significantly more seed yield of sesamum. At F₂, W₀ and W₂, both being statistically similar, was the best. F₂W₀, F₂W₂ and F₂W₃ being statistically similar, produced the highest sesamum seed yield than the rest of the combinations.

No residual effect of non-herbicidal weed management on growth characteristics and yield of the succeeding crop sesamum were observed due to weed management of maize. As the weed management during the preceding crop maize was non-herbicidal, its residual effect on weeds of the next crop sesamum was not observed obviously. No residual effect of hand weeding twice applied in rice on succeding blackgram was observed¹⁹. On the other hand, distinct residual effect due to fertility management in maize with enriched compost application was observed which was reflected in significantly improved LAI, significantly lesser days to 50% flowering and higher grain yield in sesamum. Positive residual effects of organic manures in succeeding crops following maize have been reported^26,10,27. Regarding the significant residual effect of fertility management during maize on growth characteristics of sesamum, it may be explained that due to slow release of nutrients from enriched compost during maize, the residual effect might have been obtained during sesamum. Manures have manifold benefits on the soil physical, chemical and biological characters²⁸ and have the ability to supply plant nutrient for two or more crop seasons²⁹.

Therefore, growth characteristics and seed yield of sesamum showed significant improvement due to residual effect of application of enriched compost @ 2.5 and 5.0 t/ha compared to non application of enriched compost.

Comparative economics of the treatments in maize-sesamum cropping sequence

The comparative economics of the treatments in respect of maize-sesamum cropping sequence has been presented in Table 7. It revealed that higher gross return (`292078.33/ha and `255858.67/ha in 2013 and 2014, respectively) and net return (`190310.33/ha and `154090.67/ha) of the sequence were due to application of F₂W₁ but benefit: cost ratio (2.56 and 2.16 in 2013 and 2014, respectively) was more due to application of F₁W₁.

Table 7: Comparative Economics of the Treatments in Maize-Sesamum Cropping Sequence

Fertility level                                                  Weed level                                                                        Price (`)

F₀:  Control                                                                       W₀: No weeding                                                                Maize grain: 50.00/kg

F₁:  2.5t/ha Enriched compost                                 W₁: Hand hoeing and earthing up 20 and 50 DAS           Sesamum seed: 100.00/kg

F₂:  5.0t/ha Enriched compost                                 W₂: In situ cowpea mulching upto 50 DAS

 W₃: In situ blackgram mulching upto 50 DAS

The efficacy of fertility management with application of enriched compost at either 2.5 or 5.0 t/ha and weed management by non-herbicidal methods especially hand hoeing and earthing up at 20 and 50 days in maize-sesamum cropping sequence in controlling weeds and improving growth and yield of the crops has already been highlighted. That is why, application of enriched compost associated with hand hoeing and earthing up at 20 and 50 days proved to be better than the other treatment combinations in this regard. More benefit: cost ratio obtained with application of 2.5 t/ha enriched compost as compared with 5.0 t/ha application may be attributed to the lesser cost of production incurred in case of the former.

Conclusion

Management of weeds by hand hoeing and earthing up twice coupled with organic nutrition by enriched compost in maize would result in profitable maize grain yield while beneficial residual effect of enriched compost application in maize would be observed in subsequent sesamum in terms of better growth and higher seed yield.

Conflict of Interest

The authors have no conflict of interest.

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