Partitioning of photosynthates, N and P in mustard as influenced by nutrient management in fodder sorghum (Sorghum Bicolor L.) - mustard (brassica juneca L.) cropping sequence

Abstract

A field experiment was carried out to find out the effect of N, P and biofertilizers (Azotobacter and phosphate solubilizing bacteria [PSB]) on partitioning of photosynthates, N and P and growth and yield attributes and yield of fodder sorghum-mustard cropping system in north west India. It was observed that yield of fodder sorghum on fresh as well as dry weight basis obtained due to recommended dose of fertilizers (RDF, 60 kg N + 12.9 kg P ha⁻¹) and half RDF + biofertilizers was not only highest but also significantly higher than that of half RDF and control. However, N and P uptake by fodder sorghum was significantly higher when supplied with RDF. Results on the succeeding crop of mustard showed that stems had a maximum share in total dry matter accumulation regardless of nutrient management practices. Up to 90 days after sowing (DAS), the total phytomass accumulation of mustard was statistically equal under previously applied RDF and half RDF + biofertilizers treatments. At later stages, RDF produced significantly higher dry matter accumulation. Regarding directly applied nutrients, RDF (80 kg N + 17.2 kg P ha⁻¹) produced the highest phytomass throughout the crop growth period of mustard. Mustard crop gave significantly higher seed yield due to residual and directly applied RDF as compared to that of other residual and directly applied nutrients, respectively barring half RDF + biofertilizers. Only 22.5 – 24.0% of phytosynthates transformed into sink, i.e. harvest index (HI). However, more than 80% of N was partitioned into grain (HI_N). Available N had a negative effect on nitrogen use-efficiency (NUE). Agronomic efficiency and apparent recovery of N in mustard were highest due to directly applied half RDF + biofertilizers.

Keywords:

• Agronomic efficiency
• apparent recovery efficiency of N
• biofertilizers
• fodder sorghum-mustard cropping system
• nitrogen
• nitrogen use efficiency
• HI_N
• partitioning
• phosphorus
• photosynthates

Acknowledgements

The author greatly acknowledges the financial assistance received in the form of Senior Research Fellowship from the Director, Indian Agricultural Research Institute, New Delhi, during his Doctor of Philosophy degree programme. Thanks are also due to the Head of Division of Agronomy for providing the necessary field and laboratory facilities during the course of the investigation.