Black pepper (Piper nigrum L.) is an important spice used in cooking and medicine. It is cultivated in more than 20 countries in Asia, Africa and Latin America. India is a major producer, consumer and exporter of black pepper. Leaf area (LA) is an indicator of crop growth and productivity. This study was undertaken to develop a method of estimating the individual LA of black pepper directly without the necessity for time-consuming area measurements. Ten black pepper lines were used in the study. Ninety matured leaves were collected from each line and an allometric relationship was derived by logarithmic transformation between actual leaf area (ALA) measured using the electronic leaf area meter LI-3000 A (LI-COR, Inc., Lincoln, NB) and leaf length (LL). The correlation coefficient (r) between ALA and LL ranged between 0.8692 and 0.9644 and the standard error (S.E.) between 0.0822 and 0.1149. The allometric models for 10 lines were: Panniyur 1, LA ¼ 0.7114 (LL) 1.8409 ; Panniyur 2, LA ¼ 0.3692 (LL) 2.067 ; Panniyur 3, LA ¼ 0.6148 (LL) 1.8838 ; Panniyur 4, LA ¼ 0.8355 (LL) 1.7694 ; Sreekara, LA ¼ 0.8984 (LL) 1.6692 ; Subhakara, LA ¼ 0.8384 (LL) 1.738 ; Panchami, LA ¼ 0.3691 (LL) 2.0749 ; Pournami, LA ¼ 0.4487 (LL) 1.9718 ; Kottanadan, LA ¼ 0.3474 (LL) 2.0634 ; P-24, LA ¼ 0.7579 (LL) 1.654 . These allometric models were used to calculate LA, which was then compared with the actual LA, and the correlation coefficient (r) between them was found to be > 0.99. These allometric models can be used to estimate the LA of individual leaves of black pepper. The approximate total LA of a vine can be obtained using following formula: total leaf area of black pepper vine (cm 2 ) ¼ number of laterals per vine · number of leaves per lateral · leaf area of individual leaf.

Rice is the staple food in many countries and is grown in varied climates from per‐humid to semiarid areas. Crop–weather models were used to predict rice yield in India. However, in spite of a significant influence of solar radiation on rice yield, none of these models used solar radiation as one of the predictors. In this paper, an attempt was made to predict the first season (June–September) rice yield at Coimbatore, Tamil Nadu, India by including solar radiation as one of the predictors. Ten years (1987/88–1996/97) data were used for the study. Seven predictors viz., percentage of rice area during first season (X1), number of days with minimum temperature below 22 °C in August and September (X2), average daily maximum temperature for three months (July, August and September; X3), average daily minimum temperature for three months (July, August and September; X4), total of average sunshine hours in August and September (X5), and total rainfall of July, August and September (X6) total average solar radiation of August and September (X7) were selected based on earlier report. Full model and stepwise regression analysis were performed using MSTAT computer package. The full model regression without solar radiation as predictor (Model I) recorded comparatively less R2 (0.6292). Inclusion of solar radiation (Model II) enhanced the R2 value considerably (R2=0.9464). Seven variables were further subjected to stepwise regression analysis and only four predictors were retained in the final model (Model III) with an R2 value of 0.9234. The model III with minimum parameters Y=22119.5758 + 19.6898, X1 − 150.9261, X2 − 1126.7501, X4 + 0.7179 X7 can be used to predict the first season rice yield (Y) at Coimbatore, India.

Field experiments were conducted at the Sugarcane Breeding Institute, Coimbatore, India during 1989–93 to study the productivity and water use efficiency of sugarcane under different methods of irrigation. The results showed that there could be a 44 % saving in water with higher water use efficiency in drip irrigation compared to conventional furrow irrigation. Among drip irrigation systems in the plant crop, sub surface drip (Biwall) at 40/140 cm spacing recorded a significantly higher number of millable canes, cane length and single cane weight compared to either conventional furrow irrigation or furrow irrigation based on IW/CPE (Irrigation Water Cumulative Pan Evaporation) ratio. In ratoon crop, Biwall irrigation at 60/120 cm gave significantly higher cane length and single cane weight compared to any other methods of irrigation. However, cane and sugar yields in Biwall irrigations were on par with conventional furrow irrigation but superior to either surface drip or furrow irrigation based in IW/CPE ratio.

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The predicted damage and yield loss under field conditions caused by rice leaffolder (Cnaphalocrocis medinalis) Guenee to the rice cultivar IR 50 was more in the unprotected crop than in protected crop. The yield loss was more when the infestation occurred at 40 days after sowing (DAS) than at 30,60 and 80 DAS. The damage and yield loss was not concomitant with the larval population. The economics of protection of grain crop showed that the protection was not necessary when the crop was infested at 30, 60 and 80 DAS while at 40 DAS the protection was necessary. A seed crop may warrant protection of the crop at both 30 and 40 DAS.