A field experiment was conducted from 1985-1986 to 2002-2003 on Vertisols under rainfed conditions to evaluate the effect of cropping systems and application of fertilizers and manure on seed cotton yield. To determine the long-term effects, trends and stability analyses were performed. Soil samples (0-0.15 and 0.15-0.30 m) were collected at the end of year 18 and analysed for available P and AB-DTPA extractable Zn. Among cropping systems, Asiatic diploid cotton (Gossypium arboreum) yielded 233 kg ha )1 more seed cotton than the upland tetraploid cotton (Gossypium hirsutum). Yield trend was positive for G. arboreum compared with G. hirsutum. However, the slope was not significant. Stability analyses indicated overall higher yield stability for G. arboreum than G. hirsutum. Compared with monocropping G. hirsutum, G. hirsutum-sorghum (Sorghum bicolor L.) (H-S) rotation was significantly more stable. Soil samples (0-0.30 m) of the manure-amended plots had significantly greater P and Zn content (above the critical limit) compared to those receiving inorganic fertilizers alone. With regard to nutrient management practices, seed cotton yield was the highest for the integrated nutrient management (INM) treatment receiving a combination of organic and inorganic fertilizers. Among primary nutrients, the effect of P was significant while that of K was not. Balanced fertilizer application was significantly better than treatments receiving N and NK. Yield trends were, in general, not significant. However, a positive trend was noticed for treatments receiving manure compared to fertilizer alone. Stability analysis, on the other hand, indicated that the slopes were, in general, significant. Among the nutrients, mean yield response with and without P was 1007 and 672 kg ha )1 respectively. Combined application of manure and fertilizer (INM) resulted in the highest mean yield response (1218 kg ha )1 ) and the slope was highly significant (P < 0.004). In the manureamended plots, a better nutrient status probably imparted a greater degree of yield stability. The present study suggests that compared to trend analysis, stability analysis being sensitive as it recognizes the treatment · environment interaction, is a better option to interpret results from long-term agronomic experiments.
Asiatic cotton (Gossypium arboreum) is mostly grown in the rainfed regions of India. However, little is known about the effects of nutrient-management practices on plant growth and fruiting pattern of Asiatic cotton. Therefore, plant growth and fruiting pattern under four nutrient-management treatments, N, NPK, FYM (10 Mg ha -1 ), and INM (integrated nutrient management: a combination of NPK and FYM) were quantified during 2000-01 to 2002-03 (years 16 to 18 of a longterm field experiment). Plants of the INM and FYM treatments were taller (68.4-149.5 cm) and had more main stem nodes per plant (30.5-44.5) as compared to N and NPK treatments. In treatment N, the shortest plants (50.9-83.6 cm) and the least number of fruiting structures were produced. Plants of the INM and FYM treatments accumulated more squares and bolls. Maximum boll production was 10-19 days earlier with the manure-amended than the N and NPK treatments. Treat-ment N had the lowest seed cotton yield (639-790 kg ha -1 ), because of small boll size (1.48-1.73 g) and few open bolls. Seed cotton yield followed the trend: NPK (815-1278 kg ha -1 ) < INM (776-1551 kg ha -1 ) < FYM (902-1593 kg ha -1 ). Water stress and nutrient deficiencies (P and Zn in the N and Zn in the NPK treatments) as a consequence of nutrient depletion over the years may have decreased seed cotton yields in treatments that received mineral fertilizer alone in comparison with manure-amended treatments. On a longterm basis, FYM application should therefore form an integral part of nutrient recommendation.
Tests of hypothesis of the parameter of the reduced exponential distribution E(a, ) has been studied from a conditional viewpoint, based on the conditionality principle of R. A. Fisher. It is shown that conditionally, optimal tests are possible though unconditionally no such test exists. Some desirable properties of the conditional test and large sample approximations to the upper percentile point of the conditional test statistic are also presented. The equivalence of two ancillaries for conditioning with respect to power criterion is shown.
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