Seed yield, economics, sustainability and soil fertility as influenced by long-term nutrient management in soybean (Glycine max)–sunflower (Helianthus annuus) cropping system in Vertisols

A field experiment was conducted during 1999–2011, on fixed site at Latur, to assess the nutrient requirement of soybean [Glycine max (L.) Merr.]–sunflower (Helianthus annuus L.) cropping system with different combinations of organic and inorganic nutrient management in Vertisols. Twelve treatment combinations were applied on cropping system basis for rainy (kharif) season soybean followed by winter (rabi) sunflower. Application of 100% recommended NPK + FYM 5 t/ha to kharif soybean and 100% recommended NPK to rabi sunflower recorded higher seed yield of soybean (2.33 t/ha), sunflower (1.44 kg/ha) and total system productivity in terms of sunflowerequivalent yield (3.33 t/ha). This combination also showed higher production efficiency (16.7 kg/ha/day) sustainable-yield index (0.50), and net monetary returns ( 41.1 × 10³/ha), and was statistically similar to the application of 150% NPK to both the crops in sequence. Application of FYM 5 t/ha continuously over the period of 13 years along with 100% NPK to kharif soybean and 100% NPK to rabi sunflower in sequence improved the soil fertility in terms of organic carbon, available nitrogen, phosphorus and potassium.