Effect of Land Configuration and Weed Management on Performance of Urdbean [Vigna mungo (L.) Hepper]

Pluses occupy a unique position in every system of Indian farming as a main, catch, cover, green manure and intercrop. They have played a very important role in human diet of our country as a source of protein (24.04%), carbohydrate (60%), fat (1.5%), amino acids, phosphoric acids, vitamins and minerals consumed in the form of “dal”. Urdbean/black gram (Vigna mungo L.) is a major pulse crop of the kharif season. It is one of the important pulse crop grown in India with acreage of about 4.5 million hectares and production of 2.8 million tonnes with an average productivity of 628 kg ha^-1. Whereas, in Andhra Pradesh the urdbean is grown under a total area of 5.0 lakh hectares with total production of 3.3 lakh tonnes. The average productivity of blackgram in AP is 664 kg ha^-1 (2016-17). Under rainfed situations low yields were realized due to terminal moisture stress at flowering stage. Hence, there is a need to retain the moisture in the soil for longer period and suitable land configuration measures may be developed for storage of surplus moisture. Sowing method is very useful in the pulses for better production, growth and yield. Broad bed furrows had greater positive influence on the plant height and root length over farmers practice. Blackgram is an important crop among kharif pulses and is usually grown on marginal and sub-marginal lands without weed management. Weeds reduce yield of urdbean to the extent of 78 per cent, mechanical or manual weeding is normally tedious, labour consuming and costlier. Keeping this in view, the present study was carried out to investigate integrated effect of land configuration and weed management regimes on productivity of urdbean.

A field experiment was conducted during kharif season of 2016 and 2017 at Regional Agricultural Research Station, Lam, Guntur of ANGRAU, with the mean annual rainfall was about 785 mm located at a latitude of 16o18’ North and longitude of 80^o29’ East with an elevation of 33 meters of above mean sea level (MSL). The experimental field was well drained with deep black clay loam texture. The soil of the experimental field was slightly alkaline in reaction (pH 7.6), low in organic carbon (0.48%) and available nitrogen (208.6 kg ha^-1), high in available phosphorus (38.21 kg ha^-1) and available potassium (729.5 kg ha^-1) with an electrical conductivity of 1.34 dSm^-1. The treatments comprised of two land configurations i.e., flat bed method and broad bed furrow method allotted as horizontal plots and four weed management practices i.e., weedy check, pendimethalin 30 EC @ 1.0 kg ha^-1 PE, imazethapyr 10% SL @ 55 g ha^-1 at 15-20 DAS and pendimethalin 30 EC @ 1.0 kg ha^-1 PE fb imazethapyr 10% SL @ 55 g ha^-1 at 15-20 DAS allotted as vertical plots which were replicated four times in a strip plot design. Recommended dose of N (20 kg ha^-1) and P₂O₅ (50 kg ha^-1) were applied as basal through Urea (46% N) and single super phosphate (16% P₂O₅), respectively. The seed of urdbean variety PU-31 was sown @ 25 kg ha^-1 on July 15, 2016 and July14, 2017, respectively with 30 cm × 10 cm spacing. All agronomic operations except those under study were kept normal and uniform for all the treatments. A total of 599 and 507.4 mm rainfall was received during crop growing season of kharif 2016 and 2017, respectively.
       
Weed population and weed dry weight was recorded at 50 DAS. The weed population was taken with the help of iron frame of 1 m² from 2 places of each plot and then averaged. Weed dry weights recorded by placing them in hot air oven and weed control efficiency (WCE) was calculated.  
Gross returns were calculated by taking sale price of urdbean Rs.65/- and Rs.70/- per kg in 2016 and 2017, respectively. Net returns were calculated by subtracting cost of cultivation including the cost of individual treatments from gross returns. Benefit: cost ratio was calculated after dividing net returns with the cost of cultivation. The plant height, branches plant^-1, number of pods plant^-1, test weight and grain yield were recorded. Data collected were analyzed by using standard statistical procedures. The comparison of treatment means was made by critical difference (CD) at P<0.05.

Weed dynamics
 
Weed flora emerged during the period of experimentation were grasses like, Cynodon dactylon, Dactyloctenium aegyptium, Echinichloa colona, Digitaria sanguinalis, Brachiaria sp., sedges like Cyperus rotundus and broad leaved weeds like Amaranthus viridis, Digera arvensis, Parthenium hysterophorus, Phyllanthus niruri, Trianthema portulacastrum, Acalypha indica and Abutilon indicum, Corchoru sp.
       
Experimental results revealed that crop establishment techniques viz., flat bed method and broad bed furrow method of land configuration had significant effect on weed count, weed dry weight and nodule count during first year of study. However, among the weed management practices, in the uncontrolled weedy check plot, the highest weed count (87.2 m^-2) and weed dry weight (90.9 g m^-2) were noticed and were significantly superior over all other treatments. The lowest weed count (11.3 m^-2) and weed dry weight (11.8 g m^-2) were recorded with pendimethalin 30 EC @1.0 kg a.i ha^-1 PE followed by imazethapyr 10%SL @55 g ha^-1 POE at 15-20 DAS. Similarly, higher WCE of 87 and 72.8 as also recorded in same treatments pendimethalin 30 EC @1.0 kg a.i ha^-1 PE followed by imazethapyr 10%SL @55 g ha^-1 POE at 15-20 DAS and  imazethapyr 10%SL @55 g ha^-1 POE at 15-20 DAS, respectively. Higher weed control efficiency and long lasting effects in reducing weed population and weed dry weight might be due to weed seed damage caused by pre-emergence application of pendimethalin 30 EC @1.0 kg a.i ha^-1 and suppression of established plants of both narrow and broad leaved weeds by imazethapyr and its greater efficiency to retard cell division of meristems as a result of which weeds died very rapidly. Fayaz et al., (2017) also reported similar results of effective control in weed population, weed dry matter and higher weed control efficiency (WCE) in mungbean.
 
Growth parameters
 
Land configuration practices brought significant influence on plant height and number of branches plant^-1. A significant increase in plant height (40.0 cm) and number of branches plant^-1 (7.0) were measured under broad bed furrow method over flatbed method (Table 1). This might be due to better availability of nutrients and moisture to the crop and less competition for natural resources. Similar results of higher plant height and branches plant^-1 were also reported earlier by Pandey et al., (2018) in broad bed furrow method than flat bed method of land configuration. Whereas, among weed management practices, maximum plant height (38.9 cm) was recorded with spraying of pendimethalin 30 EC @ 1.0 kg a.i ha^-1 PE fb imazethapyr 10% SL @ 55 g ha^-1 at 15-20 DAS which was statistically comparable with spraying of  imazethapyr 10% SL @ 55 g ha^-1 at 15-20 DAS and found significantly higher over other two weed management practices. The more number of branches plant-1 (6.3) were recorded with spraying of pendimethalin 30 EC @ 1.0 kg a.i ha^-1 PE fb imazethapyr 10% SL @ 55 g ha^-1 at 15-20 DAS which was significantly superior over other treatments (Table 1). Similar results of higher growth reported earlier by Teja et al., (2017) with chemical weed control than weedy check in blackgram.
 

 
Nodule count
 
Nodule count was recorded at 45 DAS indicated that nodule formation was more favored with non-herbicidal plots than herbicide treated plots (Table 1). Higher number of nodules (15.0 plant^-1) was recorded under broad bed furrow method than flat bed method of land configuration. It might be due to better availability of nutrients and moisture to the crop plants and less competition for natural resources as evident from the beneficial effects on crop growth. Among the weed management practices, in weedy check plot the maximum number of nodules plant^-1 (18.4) were recorded than rest of the treatments. It might be due to the interference of herbicide in the rhizobium-plant relationship. Strong nodulation either in chemical free treatment could be due to direct or indirect effect of herbicide to the symbiotic association of urd and rhizobium there by inhibiting nitrogenase activity. Fayaz et al., (2017) also reported similar results of higher number of nodule count plant^-1 with broad bed method of land configuration and weedy check plot in mungbean.   
 
Yield attributes and yield
 
In the present investigation, the broad bed furrow method recorded significantly higher number of pods plant^-1 (26.9) and maximum test weight (4.9 g) compared to flat bed method. Pandey et al., (2018) also reported similar results of higher pods plant^-1 in blackgram. The weed management practices significantly influenced the yield parameters where maximum number of pods plant^-1 (26.0) and test weight (4.8g) were recorded with spraying of pendimethalin 30 EC @ 1.0 kg a.i ha^-1 PE fb imazethapyr 10% SL @ 55 g ha^-1 at 15-20 DAS which was statistically on a par with spraying of  imazethapyr 10% SL @ 55 g ha^-1 at 15-20 DAS and significantly higher than weedy check and pendimethalin 30 EC @ 1.0 kg a.i ha^-1 PE (Table 1). The highest number of pods plant-1 and test weight were recorded in weed management practices might be due to more space available for crop and lower competition as compared to weedy check (Table 1).
       
Significantly higher grain yield of urdbean (1064 kg ha^-1) was obtained with adoption of broad bed furrow method over flat bed method (943 kg ha^-1). A yield advantage of 12.8 per cent with broad bed furrow method of land configuration than that of flat bed method.  This might be due to the fact that under favourable soil conditions, the plant accumulates and translocates the photosynthates from source to sink more efficiently which in turn increased all the growth and yield attributes too. Similar results of higher grain yield and straw yield were also reported earlier by Pandey et al., (2018) in blackgram. Similarly, Garud et al., (2019) and Halli and Angadi (2019) also reported more grain yield in pigeonpea and cowpea, respectively with broad bed furrow method of sowing. Whereas, the maximum grain yield (1280 kg ha^-1) was obtained with spraying of pendimethalin 30 EC @ 1.0 kg a.i ha^-1 PE fb imazethapyr 10% SL @ 55 g ha^-1 at 15-20 DAS which was significantly more than other weed management practices (Table 2). Among the weed management practices, uncontrolled weedy check resulted in 38.7 per cent reduction in grain yield of urdbean than chemical weed management. Uncontrolled weedy check recorded the lowest grain yield of 681 kg ha^-1 followed by pendimethalin 30 EC @ 1.0 kg a.i ha^-1 PE alone (978 kg ha^-1) and imazethapyr 10% SL @ 55 g ha^-1 alone at 15-20 DAS (1074 kg ha^-1). The reduction in yield under weedy check treatment might be due to more crop weed competition throughout the crop growth period for nutrients as well as moisture and reduction of yield attributing characters. Higher grain yields in chemical weed management practices may be attributed due to effective and timely weed management under these treatments reduced the density as well as dry weight of weeds which facilitated the crop plants to have sufficient space, light, nutrient and moisture and thus the number of pods plant^-1, test weight and finally the yield were increased. Similar results of more grain yield (Fayaz et al., 2017) are also observed in mungbean.
 

 
Economics
 
Two years pooled data shows that (Table 3) the maximum gross returns (Rs. 85,684 ha^-1) and net returns (Rs. 52,314 ha^-1) were observed with adoption of broad bed furrow method and with application of pendimethalin 30 EC @ 1.0 kg a.i ha^-1 PE fb imazethapyr 10% SL @ 55 g ha^-1 at 15-20 DAS. Whereas, the highest B:C (1.57) was noticed with adoption of broad bed furrow method and with application of pendimethalin 30 EC @ 1.0 kg a.i ha^-1 PE fb imazethapyr 10% SL @ 55 g ha^-1 at 15-20 DAS. This might be due to highest grain yield obtained with the respective treatments. Pandey et al., (2018) also reported higher B:C ratio of 1.82 in blackgram with broad bed furrow method. Fayaz et al., (2017) also reported similar findings of higher B:C ratio (1.96) in mungbean.
 

Based on the experimental findings, it can be concluded that broad bed method of land configuration for sowing proved its superiority over flat bed method by producing 12.8 per cent higher grain yield besides empowering growth and yield attributes. Among the weed management practices, the highest grain yield (1280 kg ha^-1) recorded with pendimethalin 30 EC @ 1.0 kg a.i ha^-1 PE fb imazethapyr 10% SL @ 55 g ha^-1 at 15-20 DAS along with maximum monetary returns and B:C can be recommended for urdbean. Overall, an yield advantage of 12.8 per cent with broad bed furrow method of land configuration and 63.1 per cent with chemical weed management.