Soil Fertility and Nitrogen Economy in Legume Wheat Sequences
Loading...
Date
1997
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Birsa Agricultural University, Ranchi
Abstract
Title: "Soil fertility and nitrogen economy in legume-wheat sequences"
With a theme to slash-down the application of nitrogen nutrient through chemical fertilizer in a crop and cropping sequence, exploitation of biological source of nitrogen, and maintaining the soil health for a sustainable crop production is a call of the day. As per 1991-92 fertilizer census, 18% short in nitrogenous fertilizers was reported. Even during 1996-97 a marked fall in (21%) production of nitrogenous fertilizers was reported in comparison to 1995-96. Hence, the present investigation was carried out to assess the contribution of legumes as a biological source of nitrogen for a stable wheat production.
In the present studies, five cropping sequences, (main plot, viz: soybean-wheat, cowpea-wheat, blackgram-wheat, stylo-wheat and rice-wheat) and five nitrogen levels (sub-plot, viz: No N25, N50 N75 and N100% of the recommended dose for wheat), thus altogether twentyfive treatments were put in split plot design and replicated thrice, during 1993-94 and 1994-95. The soil of the experimental plots were Silt Loam in texture (Sand, 37.72; Silt 51.10, Clay 11.18% respectively). It was low in Organic Carbon, available N, P and medium in K with PH 6.1.
The results of two years of investigation revealed that legumes in general and blackgram in particular significantly contributed towards yield and yield contributing characters in wheat. Accordingly blackgram as a preceding crop to wheat significantly produced maximum grain yield (31.32 qha") of wheat. Wheat yield obtained at 75% recommended dose of nitrogen was statistically tantamount to wheat yield received in presence of 100% Na
Introduction of legumes, further enhanced the O/C (%), available N, P and K in general and blackgram in particular enriched the soil fertility in a better way over rest of the legumes. These fertility indices contributed about 95.75 to 96.84 % towards wheat yield during the respective years.
The cropping sequences, comprised of legumes also harvested the maximum amount of N, P and K nutrients. Thus, soybean-wheat harvested the maximum quantity of N and P while stylo-wheat harvested the maximum quantity of K. Although, wheat grown after blackgram harvested the maximum N and P but soybean being a more proteinous component gave higher yield of nitrogen, which resulted in overall higher harvest of nitrogen by soybean-wheat sequence. Accordingly, better biomass production by stylo resulted in higher removal of K by stylo-wheat sequence. Increasing trend in N-levels also increased the nutrients removal by different cropping sequences, however, under all the situations, the interaction of cropping sequences and N-levels was not significant
The balance-sheet of the fate of nutrients further revealed that under all the legumes based cropping sequences, a positive gain in nitrogen nutrients while fixation of phosphorus under all,
the sequences and further gain of potassium were accounted.
Though wheat after blackgram produced significantly higher yield over rest of the sequences however, in terms of wheat equivalent yield, stylo-wheat accounted for significantly maximum yield (68.59 qha ¹) due to higher biomass production, and cost of green forage yield of stylo, while application of 75% N accounted for statistically similar wheat equivalent yield (55.32 qha) to 100% N (57.20 qha"). Although, wheat after blackgram produced more protein but soybean-wheat sequence as a whole resulted in significantly higher protein harvest over rest of the sequences (718.42 Kg.ha 1), 75% of N further recorded on par protein yield to what was recorded at 100% N.
Stylo-wheat sequencedue to higher biomass production resulted in the maximum production of energy which was closely followed by the energy produced by blackgram-wheat sequence. Application of 75% N resulted in higher energy productivity than it was recorded in presence of 100% N
Grain yield of wheat under all the different sequences gave a linear response to nitrogen application. The wheat yield above 75% N was found to be static. Among the sequences, blackgram-wheat accounted for better yield of wheat at each level of nitrogen. Stylo-wheat sequence was more remunerative since, it accounted for maximum net return (Rs. 12,850.00 ha) as well as maximum net return to per rupee investment (1.13). Income received at 75 and 100% N was statistically equal.
Performance of wheat grown after legume under 75% nitrogen was more stable since, this accounted for more grain yield over the sequence mean with regression coefficient nearer to unity (bi 1.0) and deviation from regression line resulted to zoro (0). The stability of soil nitrogen status after the completion of two years of experimentation revealed that fertility left over by legume-wheat sequence under 75 % N was more stable. Thus, wheat after blackgram under 75% nitrogen produced maximum
wheat yield but in terms of wheat equivalent yield, stylo-wheat sequence resulted in more remunerative sequence over rest of the sequences which also accounted for higher energy production and net return to per rupee investment. Blackgram-wheat sequence was more stable in terms of wheat yield and nitrogen build-up in the soil system.