Long-term yield trend and sustainability of rainfed soybean–wheat system through farmyard manure application in a sandy loam soil of the Indian Himalayas

A long-term (30 years) soybean–wheat experiment was conducted at Hawalbagh, Almora, India to study the effects of organic and inorganic sources of nutrients on grain yield trends of rainfed soybean (Glycine max)–wheat (Triticum aestivum) system and nutrient status (soil C, N, P and K) in a sandy loam soil (Typic Haplaquept). The unfertilized plot supported 0.56 Mg ha⁻¹ of soybean yield and 0.71 Mg ha⁻¹ of wheat yield (average yield of 30 years). Soybean responded to inorganic NPK application and the yield increased significantly to 0.87 Mg ha⁻¹ with NPK. Maximum yields of soybean (2.84 Mg ha⁻¹) and residual wheat (1.88 Mg ha⁻¹) were obtained in the plots under NPK + farmyard manure (FYM) treatment, which were significantly higher than yields observed under other treatments. Soybean yields in the plots under the unfertilized and the inorganic fertilizer treatments decreased with time, whereas yields increased significantly in the plots under N + FYM and NPK + FYM treatments. At the end of 30 years, total soil organic C (SOC) and total N concentrations increased in all the treatments. Soils under NPK + FYM-treated plots contained higher SOC and total N by 89 and 58% in the 0–45 cm soil layer, respectively, over that of the initial status. Hence, the decline in yields might be due to decline in available P and K status of soil. Combined use of NPK and FYM increased SOC, oxidizable SOC, total N, total P, Olsen P, and ammonium acetate exchangeable K by 37.8, 42.0, 20.8, 30.2, 25.0, and 52.7%, respectively, at 0–45 cm soil layer compared to application of NPK through inorganic fertilizers. However, the soil profiles under all the treatments had a net loss of nonexchangeable K, ranging from 172 kg ha⁻¹ under treatment NK to a maximum of 960 kg ha⁻¹ under NPK + FYM after 30 years of cropping. Depletion of available P and K might have contributed to the soybean yield decline in treatments where manure was not applied. The study also showed that although the combined NPK and FYM application sustained long-term productivity of the soybean–wheat system, increased K input is required to maintain soil nonexchangeable K level.     

Effect of tropical browse leaves supplementation on rumen enzymes of sheep and goats fed <Emphasis Type="Italic">Dichanthium annulatum</Emphasis> grass-based diets

In a switch-over experiment, eight male animals, four each of sheep and goats of local breeds with mean body weight of 26. 8 ± 2.0 and 30.0 ± 2.1 kg, were fed Dichanthium annulatum (DA) grass and four browse species viz. Helictris isora, Securengia virosa, Leucaena leucocephala (LL) and Hardwickia binnata (HB) in four feeding trials to assess their supplementary effect on activity of rumen enzymes. The sheep and goats were offered DA grass with individual browse in 75:25 and 50:50 proportions, respectively, for more than 3 months during each feeding trial, and rumen liquor samples were collected twice at 0 and 4 h post feeding after 60 and 90 days of feeding. Glutamate oxaloacetate transaminase (GOT), glutamate pyruvate transaminase (GPT) and glutamate dehydrogenase (GDH) enzymes were determined in the bacteria and protozoa fractions of rumen liquor, while cellulase enzyme activity was measured in mixed rumen liquor. LL and HB had the highest and lowest contents of CP, while fibre contents were lower in early than later browse leaves. Supplementation of browse leaves significantly (P < 0.05) affect the specific activity of GDH enzyme in bacteria fraction of rumen liquor of animal species, while GDH activity was similar in protozoa fraction of rumen liquor of sheep and goats on all DA grass–browse-supplemented diets except DA–HB (42.8 units/mg protein), where activity was significantly (P < 0.05) low. Specific activities of GOT and GPT enzymes in both bacteria and protozoa fractions of rumen liquor differ significantly (P < 0.05) due to supplementation of browse leaves to DA grass. Browse leaves significantly (P < 0.05) affect the cellulase enzyme activity in animal rumen liquor, being highest on DA–LL (193.4) and lowest on DA–HB diet (144.8 μg sugar/mg protein). Goat exhibited higher activities of GOT and GPT than sheep in both bacteria and protozoa fraction of rumen liquor, while cellulase activity was similar between the animal species on the grass–browse leaves diets. Results indicate that browse leaves supplementation affect the enzyme activities of sheep and goats rumen, while the goats rumen liquor had higher activities of GOT, GPT and GDH enzyme than sheep.