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Assessing crop N status of fertigated vegetable crops using plant and soil monitoring techniques
Author(s) -
PeñaFleitas M.T.,
Gallardo M.,
Thompson R.B.,
Farneselli M.,
Padilla F.M.
Publication year - 2015
Publication title -
annals of applied biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.677
H-Index - 80
eISSN - 1744-7348
pISSN - 0003-4746
DOI - 10.1111/aab.12235
Subject(s) - petiole (insect anatomy) , crop , agronomy , biology , nutrient , crop yield , horticulture , mathematics , botany , ecology , hymenoptera
Evaluation of crop N status will assist optimal N management of intensive vegetable production. Simple procedures for monitoring crop N status such as petiole sap [ NO 3 − –N], leaf N content and soil solution [ NO 3 − ] were evaluated with indeterminate tomato and muskmelon. Their sensitivity to assess crop N status throughout each crop was evaluated using linear regression analysis against nitrogen nutrition index ( NNI ) and crop N content. NNI is the ratio between the actual and the critical crop N contents (critical N content is the minimum N content necessary to achieve maximum growth), and is an established indicator of crop N status. Nutrient solutions with four different N concentrations (treatments N1–N4 ) were applied throughout each crop. Average applied N concentrations were 1, 5, 13 and 22 mmol L −1 in tomato, and 2, 7, 13 and 21 mmol L −1 in muskmelon. Respective rates of N were 23, 147, 421 and 672 kg N ha −1 in tomato, and 28, 124, 245 and 380 kg N ha −1 in muskmelon. For each N treatment in each crop, petiole sap [ NO 3 − –N] was relatively constant throughout the crop. During both crops, there were very significant ( P < 0.001) linear relationships between both petiole sap [ NO 3 − –N] and leaf N content with NNI and with crop N content. In indeterminate tomato, petiole sap [ NO 3 − –N] was very strongly linearly related to NNI ( R 2 = 0.88–0.95, P < 0.001) with very similar slope and intercept values on all dates. Very similar relationships were obtained from published data of processing tomato. A single linear regression ( R 2 = 0.77, P < 0.001) described the relationship between sap [ NO 3 − –N] and NNI for both indeterminate and processing tomato, each grown under very different conditions. A single sap [ NO 3 − –N] sufficiency value of 1050 mg N L −1 was subsequently derived for optimal crop N nutrition (at NNI = 1) of tomato grown under different conditions. In muskmelon, petiole sap [ NO 3 − –N] was strongly linearly related to NNI ( R 2 = 0.75 – 0.88, P < 0.001) with very similar slope and intercept values for much of the crop (44–72 DAT , days after transplanting). A single linear relationship between sap [ NO 3 − –N] and NNI ( R 2 = 0.77, P < 0.001) was derived for this period, but sap sufficiency values could not be derived for muskmelon as NNI values were >1. Relationships between petiole sap [ NO 3 − –N] with crop N content, and leaf N content with both NNI and crop N content had variable slopes and intercept values during the indeterminate tomato and the muskmelon crops. Soil solution [ NO 3 − ] in the root zone was not a sensitive indicator of crop N status. Of the three systems examined for monitoring crop/soil N status, petiole sap [ NO 3 − –N] is suggested to be the most useful because of its sensitivity to crop N status and because it can be rapidly analysed on the farm.