Abstract: An experiment consisting of three levels of phosphorus (0, 30, 60 kg P2O5 ha-l) and six harvesting dates (starting from 20 days after flowering, at 5-day interval) was conducted at the field near Pal village, Jodhpur, Rajasthan (India) to assess their effects on yield and quality of moth bean. Application of 30 and 60 kg P2O5 ha-l increased the mean seed yield by 5.8 and 9.7% over no phosphorus application. Harvesting moth bean at 20 Days After Flowering (DAF) gave a mean yield of 449 kg ha-l. Seed yield progressively increased with delay in harvesting and was maximum when harvested at 40 DAF (705 kg ha-l). A further delay of 5 days in harvesting (i.e., at 45 DAF) resulted in mean yield loss of 14%. Application of 60 kg P2O5 ha-l resulted in higher split percentage (68.9%), more milling yield (82.5%), better husking efficiency (34.5%), higher head-dal yield (46.7%) and lower broken percentage (18.0%) as against 62.8, 78.9, 26.8, 37.2 and 22.0%, respectively, without the use of phosphorus. Better milling parameters were obtained when the crop was harvested at 30 DAF. Maximum crude protein was recorded when the crop was harvested at 35 DAF. Feeding trials on albino rats revealed that the pulse gave the maximum biological value of protein (47.05%) when the crop was harvested at 30 DAF with application of 60 kg P2O5. The biological value was lowest when phosphorus was not applied to the crop. Phosphorus application also resulted in increased value of net protein utilization. The study indicated that reasonable yield levels, milling parameters and protein quality could be obtained if the crop is harvested between 30 and 40 DAF.
INTRODUCTION
Grain legumes provide vegetarians with a significant amount of their dietary protein requirements. Even In case of non-vegetarians, legumes remain to be major source of proteins (Mertia et al., 2006; Guillon and Champ, 1996). These are good sources of vitamins and minerals in addition to calories and proteins (Duranti and Gius, 1997). Moth bean (Vigna aconitifolia (Jecq.) Marechal) is an important crop of arid regions. However, effect of fertilizers and other agronomic practices on quality parameters has not been investigated in detail (Bhansali et al., 2004). The grain moisture content is supposed to have a definite bearing on field and post-harvest losses, storability and milling quality of pulses. The information available on effect of agronomic practices on post harvest aspects of pulses, though important, yet is meagre (Singh, 2005). This investigation was, therefore, aimed to find out optimum harvest period besides phosphorus needs and their effects on grain yield, milling characters and protein quality with respect to time of harvest.
MATERIALS AND METHODS
An experiment was conducted at field near Pal village, Jodhpur, Rajasthan (India), for three consecutive kharif seasons on loamy sand soil having pH 8.3, organic carbon 0.24% and total nitrogen 0.06%, available phosphorus 18 kg ha-1 and available potassium 230 kg ha-1. The soil contained 86% sand, 8.2% silt and 5.6% clay and has been classified as coarse loamy, mixed, hyperthermic, camborthids according to US soil taxonomy.
A split plot design with three replications was used keeping moth bean cultivar RMO-40 as test crop Three levels of phosphorus (0, 30 and 60 kg P2O5 ha-1) in main plots and six harvesting dates (starting from 20 days after flowering at 5-day interval) were kept in sub-plots Whole of phosphorus as per treatments and 15 kg N ha-1 as starter dose were applied at the time of sowing Short spell of droughts occurred during season l at early crop stage, while during season II and III at reproductive stage and as such one supplemental irrigation (40 mm) at these stages was given in every season.
Total N in seed was determined by modified Kjeldhal method, which was multiplied by factor (6.25) to obtain crude protein content. Moth bean samples from with or without phosphorus application treatments harvested at 30 and 45 days after flowering were evaluated for protein quality by conducting feeding trials on albino rats. The collected samples were analyzed for biological value of protein (BY), True Digestibility (TD), Apparent Digestibility (AD) and Net Protein Utilization (NPU) as per Eggum (1973). The data were statistically analyzed in split plot design as per Gomez and Gomez (1984). The milling parameters were obtained with single run of laboratory model of grinding mill run by 1 HP motor
RESULTS AND DISCUSSION
Grain Yield
Application of 30 and 60 kg P2O5 ha-1 increased
the mean seed yield by 5.8 and 9.7% over no phosphorus application. The poor
response of moth bean to applied phosphorus was due to low rainfall and drought
conditions in all the seasons.
Harvesting moth bean at 20 Days After Flowering (DAF) gave a mean yield of 449 kg ha-1 (Table 1). Seed yield progressively increased up to harvesting at 40 DAF (705 kg ha-1). Thus, delay in harvesting by another 20 days resulted in increased yield by 58.8% over 20 DAF. Garg et al. (2004) reported that seeds in pod attain maximum dry weight up to 19-21 days after anthesis in moth bean. Increase in yield after 20 DAF in the present study is attributed to non-synchronous pod development in green gram. Therefore the grain yields are maximum when the grain development is complete in most of tile pods. A delay of 5 days in harvesting (at 45 DAF) resulted in mean yield loss of 14%.
| Table 1: | Influence of phosphorus and time of harvest on moth bean yield (kg ha-1) |
| DAF: Days after flowering | |
The phosphorus application increased the pod number. Application of 60 kg P2O5 ha-1 resulted in 8.5% higher pods plant-1 over control (0 kg P2O5 ha-1). The number of pods at 20 days after flowering was 16.9 per plant, which increased to 31.8 per plant when crop was harvested at 40 days after flowering. A delay in harvesting by 5 days from 40 days after flowering led to 27.8 pods per plant (14% loss of pods). The reduction in yield at delayed harvesting was mainly due to loss of pods owing to over maturity. Walsh (1991) while reviewing the causes of grain loss in mung bean found delayed harvesting as major cause of grain loss in Australia.
Milling Quality
Phosphorus application marginally improved the milling quality parameters.
Application of 60 kg P2O5 ha-1 resulted in
higher split percentage (68.9%), more milling yield (82.5%), better husking
efficiency (34.5%), higher head-dal (dehusked split) yield (46.7%) and lower
broken percentage (18.0%) as against 62.8, 78.9, 26.8, 37.2 and 22.0%, respectively,
without the use of phosphorus (Table 2). Harvesting moth bean
at 30 DAF gave better split percentage, higher total milling yield, better husking
efficiency, higher head-dal yield and lower broken percentage compared to earlier
or delayed harvesting which gave poor milling quality parameters (Table
2). The poor milling characters in early harvesting may be attributed to
pre-mature grain, while in delayed harvesting low grain moisture content played
a key role in deteriorating milling parameters. The fast drying of grains caused
very low moisture contents in grain in later harvesting, which led to higher
breakage of grains which eventually led to lower husking efficiency. Better
yield at 40 DAF and better milling parameters at 30 DAF defines a 10-day period,
i.e., between 30 and 40 DAF where reasonable yields with satisfactory milling
characters could be obtained.
Crude Protein Content
Application of phosphorus and time of harvest had no significant effect
on the crude protein content. However, crude protein (25.5%) was maximum when
crop was harvested at 35 DAF with application of 60 kg P2O5.
Singh et al. (1994) also found increased crude protein contents in seeds
of moth bean with the application of 60 kg P2O5 ha-1.
Protein Quality
Maximum biological value of protein (47.5%) was obtained when moth bean
was harvested at 30 DAF with 60 kg P2O5 ha-1
while harvesting at 30 DAF without phosphorus resulted in the lowest biological
value (44.02%). This indicates positive role of P application in enhancing protein
quality. On an average the application of phosphorus increased the biological
value from 45.08% under control to 46.62% with 60 kg P2O5
ha-1 (Table 3). Application of phosphorus also
resulted in increased value of net protein utilization.
| Table 2: | Influence of phosphorus and harvesting time on milling parameters (mean of 3 seasons) of moth bean |
| Table 3: | Protein quality of moth bean (%) as influenced by phosphorus and time of harvest (mean of 3 seasons) |
The True Digestibility (TD) and Apparent Digestibility (AD), however, decreased with application of phosphorus. Delay in harvesting from 30 to 45 DAF improved protein quality characters at both phosphorus levels except those of biological value and net protein utilization, which were higher at 30 DAF with 60 kg P2O5 ha-1 application.