ارزیابی وضعیت شاخص سبزینگی گوجه و خیار گلخانه‌ای با استفاده از حسگرهای غیرمخرب

تکنیک‌های کشاورزی دقیق در یک محیط گلخانه‌ای به افزایش کیفیت محصول نهایی، کاهش هزینه‌های استفاده از کود و جلوگیری از رواناب نیتروژن کمک می‌کند. حسگرهای نوری با اندازه‌گیری بازتاب یا جذب از برگ‌های سبز ابزاری سریع و غیرمخرب برای محاسبه محتوای سبزینگی و کلروفیل گیاه هستند. هدف از این تحقیق، بررسی قابلیت اطمینان شاخص پوشش گیاهی تفاضلی نرمال شده (ndvi) اندازه‌گیری‌شده توسط حسگر سبزینه‌سنج (greenseeker) به‌عنوان شاخص غیرمستقیم وضعیت سبزینگی گوجه و خیار گلخانه‌ای و مقایسه عملکرد این حسگر با کلروفیل‌متر (spad) بود. آزمایش در بهار سال 1396 در گلخانه تحقیقاتی گروه مهندسی بیوسیستم دانشگاه بوعلی سینا همدان انجام شد. گوجه‌فرنگی و خیار با تیمارهای کود اوره صفر، 0.028، 0.138، 0.359 و 0.607 گرم بر لیتر با محتوای 46% نیتروژن کوددهی گردید. 71 روز پس از کاشت، تیمارهای یک تا سه با کود اضافی تحت درمان قرار گرفتند. تعداد برگ گیاهان در پایان هر مرحله از داده‌برداری شمارش شدند. رابطه رگرسیونی بین متغیرهای اندازه‌گیری شده با نرم‌افزار spss محاسبه گردید. در گوجه و خیار به‌ترتیب میزان کود و ndvi 0.95 و 0.57 و کلروفیل قرائت‌شده به‌طور متوسط همبستگی 0.65 و 0.60 داشتند.

Evaluation of Vegetation Index of Greenhouse Tomato and Cucumber using nondestructive Sensors

<p > <strong >Introduction </strong > </p > <p >One of the most important factors in agricultural production is nitrogen which has a great impact on plant growing, yield performance and plant quality production. The optimum amount of nitrogen fertilizer is varied from fields to fields. There are some time consuming and costly ways to measure the nitrogen content of plants or soil, which are inappropriate for extended field or for a long growing season. Fast and remote optical sensors calculate greenness of plant using reflectance or absorbance of light from green leaves. Measuring chlorophyll with SPAD managed the nitrogen requirement for maize, Poinsettia and Nagoya Red. Whereas SPAD was not a suitable choice for chlorophyll measurement at the end of growing period. Therefore, GreenSeeker was applied as a noncontact to record the NDVI of tomato’s and cucumber’s leaves. The purpose of this research was the evaluation of GreenSeeker ability to estimate nitrogen requirement and then the plant health. </p > <p >   </p > <p > <strong >Materials and Methods </strong > </p > <p >The study was performed on Matin and Nahid cultivars of tomato and cucumber, respectively. The pots were 291 and filled with 3 kg sieved soil. The bottom layer of each pot was filled with stone for better drainage. Before planting, the soil was analyzed in order to define the ingredients. All pots put in the greenhouse with polycarbonate structure in two floors. Measurements were repeated every week with SPAD and GreensSeeker and fertigation was started 50 days after planting (DAP). In order to provide other nutrient elements, all pots got Humicacid at 37DAP and the effect was measured in 43rd DAP. Fertigation was continued until 71st DAP and first, second and third treatments were supplemented with extra fertilizer to reach the amount of fertilizer to fifth treatment. To calculate Total  Nitrogen  (TN), the concentrations of nitrateN and nitriteN are determined and added to the total  Kjeldahl nitrogen. Chlorophyll meter (SPAD) and GreenSeeker optical sensor have become available for sitespecific and needbased N management in greenhouse. The GS was located at 60 cm above the plant and measured the average NDVI. This sensor has red and NIR diodes which reflect and absorb the spectra in 660±15nm and 770±15nm regions, respectively. The SPAD values were recorded by inserting the middle portion of the index leaf in the slit of SPAD meter. As well as, chlorophyll meter can confirm the GreenSeeker output (NDVI). GreenSeeker is a suitable optical sensor because it is not affected by light and temperature variation or wind intensity. </p > <p >Statistical analyses were performed on the pooled data of both tomato and cucumber using Statistical Product and Service Solutions (SPSS). Regression equations were fitted between fertilizer and the readings recorded with different gadgets at different growth stages. </p > <p >   </p > <p > <strong >Results and Discussion </strong > </p > <p >Chlorophyll content and NDVI of tomato and cucumber increased during the growing stages except in 71st DAP for cucumber. The percentage of total nitrogen of 1 <sup >st </sup >, 2 <sup >nd </sup > and 3 <sup >rd </sup > treatments were further than two others because of supplementary fertilizer. According to the Kjeldahl result of cucumber, the 3 <sup >rd </sup > treatment had the lowest nitrogen accumulation in fruits. In addition, chlorophyll and NDVI of cucumber almost showed the increasing correlation by fertilizer enhancement while the opposite behavior was seen for tomato. That would be related to different fertilizer needs of them. The linear regression of fertilizer and reading NDVI of 2 <sup >nd </sup > to 5 <sup >th </sup > treatments were ascending. The number of increasing leaves was calculated in all pots every weeks as another studied element. Each pot had new grown leaves every weeks that was more or sometimes less than last weeks. However, accurate correlation coefficient was reported with NDVI in all treatments, whereas chlorophyll did not show a direct relation. </p > <p > <strong >   </strong > </p > <p > <strong >Conclusions </strong > </p > <p >The result of the study confirmed the useful GreanSeeker as an accurate and fast technology for prediction of NDVI. Among different fertilizer treatments of cucumber, 3 <sup >rd </sup > one showed the acceptable results. Since tomatoes did not reach to fertility stage, it would not possible to extract the best nitrogen fertilizer treatments. It is obvious that evaluation of pots in complete growth stages reach us to codify manual fertilization. </p >